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Who dares, learns: chemical inspection behaviour and acquired predator recognition in a characin fish.

Individuals that dare approach predators (predator inspection behaviour) may benefit by acquiring information regarding the potential threat of predation. Although information acquisition based on visual cues has been demonstrated for fish, it is unknown whether fish will inspect predators on the basis of chemical cues or whether such inspection behaviour results in information acquisition. Here, we first ascertained whether predator inspection behaviour can be mediated by chemical cues from predators by exposing groups of predator-naive glowlight tetras (Hemigrammus erythrozonus) to the chemical cues of a potential fish predator (convict cichlid Cichlasoma nigrofasciatum) that had been fed either tetras (which possess an alarm pheromone) or swordtails (Xiphophorus helleri, which lack Ostariophysan alarm pheromones). Tetras showed a significant increase in antipredator behaviour when exposed to the tetra-diet cue, but not when exposed to the swordtail-diet cue. Chemically mediated predator inspection behaviour was also affected. Both the latency to inspect and the minimum approach distance to the predator significantly increased, and the mean number of inspectors per predator inspection visit significantly decreased when tetras were exposed to the tetra-diet versus the swordtail-diet chemical cues. We then examined a potential benefit associated with chemically mediated predator inspection behaviour. Only tetras that were initially exposed to the tetra-diet cue and that had inspected the predator acquired the visual recognition of a convict cichlid as a predation threat. Our results thus demonstrate that (1) predator inspection behaviour in the glowlight tetra can be initiated by chemical cues, (2) chemically mediated inspection behaviour is affected by the presence of alarm pheromone, and (3) inspectors benefit by acquiring the recognition of novel predators. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

Housing and welfare in laboratory rats: effects of cage stocking density and behavioural predictors of welfare.

Using male and female Alderley Park (Wistar-derived) rats housed in single-sex groups in standard laboratory cages, we looked at the effect of group size (one, three, five or eight) on competitive behaviour and time budgeting (initial and longer term), changes in their serum testosterone (males), corticosterone and antibody concentrations, and organ pathology at age 16 weeks, together with the interrelationships between behavioural measures and pathophysiological indices of social stress. Group size had only limited long-term effects on overall time budgeting and did not affect pathophysiological responses, although there were highly significant differences between individuals in replicate cage groups. Pathophysiology within both sexes showed strong and highly specific correlations with a small subset of behaviours suggesting frustrated attempts to escape from cages, including chewing the cage bars. Escape-related behaviour also correlated strongly with one component of competitive behaviour, Aggressive Grooming within both sexes, although Aggressive Grooming correlated with pathophysiological responses only among males. Females generally showed greater escape-related behaviour associated with greater signs of pathophysiology regardless of the level of aggression shown between cagemates. Major differences in intercorrelated behavioural and pathophysiological responses between replicate groups implied that the individual composition of groups rather than their size had the greater impact on the welfare of the rats, especially among females. This may be consistent with adaptive sex differences in their competitive reproductive strategies. The frequency of apparent escape-related behaviours and Aggressive Grooming, particularly when rats are first introduced into their cage groups, may provide a simple assessment of the welfare implications of particular cage groupings. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

Behavioural studies on the effects of d-amphetamine and estradiol benzoate alone and in combination.

The effects of d-amphetamine sulphate on grooming, rearing, and ambulatory behaviour in the T-maze was studied in rats. Low doses (0.25-2.0 mg/kg) produced a dose-dependent change in behaviour; ambulatory behaviour was increased while grooming and rearing behaviour was decreased. The results suggest that the behavioural changes are a direct effect of amphetamine rather than a secondary consequence of a competition between different types of behaviour. The effects of d-amphetamine sulphate and/or estradiol benzoate on grooming, rearing, and ambulatory bheaviours in the T-maze and open field were also studied. Rats chronically treated with estradiol or oil were injected with amphetamine or saline just prior to evaluation in the maze or open field. Amphetamine treatment, irrespective of environment or hormone treatment, stimulated ambulatory behaviour while inhibiting grooming behaviour. Estradiol specificially antagonized the amphetamine induced reduction of grooming in the maze only. The results suggest that amphetamine has an independent action on T-maze behaviour whereas estradiol has an effect that depends on the environment for its manifestation.

Animals↗

Di-n-propylacetate-induced abstinence behaviour as a possible correlate of increased GABA-ergic activity in the rat.

Administration of di-n-propylacetate (DPA), an inhibitor of SSA-dehydrogenase, produces in naive rats abstinence behaviour which can be blocked by morphine and bicuculline and may be useful as a behavioural correlate of increased GABA-ergic activity. The usefulness of this model has been demonstrated by studying the effect of bicuculline, picrotoxin, strychnine, morphine, aminooxyacetic acid, 3-mercaptopropionate and thiosemicarbazide on DPA-induced abstinence behaviour. Behaviour was suppressed both by bicuculline or picrotoxin, while the selective glycine antagonist strychnine was ineffective. A comparable syndrome could not be evoked by treatment with aminooxyacetic acid, a GABA-transaminase inhibitor, indicating that the effect of DPA was not caused by inhibition of this enzyme. Instead, aminooxyacetic acid suppressed the DPA-induced abstinence behaviour, suggesting that two GABA-ergic systems with opposite effects on behaviour can be distinguished. The syndrome was also suppressed by convulsant doses of 3-mercaptopropionate, while thiosemicarbazide was ineffective. Abstinence behaviour was further suppressed by morphine with an ED50 of 0.5 mg/kg and this action could be clearly separated from its depressant effect on locomotor activity in non-treated animals. These results suggest that morphine receptors may be involved in DPA-induced abstinence behaviour. Based on these experiments a model has been proposed for GABA-ergic terminals being under the inhibitor influence of GABA-ergic autoreceptors. It is proposed that DPA-induced abstinence behaviour may be useful as a model of increased GABA-ergic activity to aid study of the regulation and properties of the GABA-ergic system in vivo.

3-Mercaptopropionic Acid↗

Associations among health-related behaviours: sociodemographic variation in Finland.

OBJECTIVES: The study examines sociodemographic variation in associations and co-occurrence of health behaviours that contribute to multifactorial chronic diseases. METHODS: Mantel-Haenszel odds ratios were used to examine pairwise associations among smoking, alcohol use, physical activity, and diet across categories of sociodemographic characteristics. Breslow-Day test for homogeneity was used to test for sociodemographic differences. In addition, co-occurrence of each two unhealthy behaviours was examined across sociodemographic groups using nationwide population survey data from 26,014 Finnish adults. RESULTS: Most of the health behaviours examined were interrelated and sociodemographic differences in the associations were few. Differences were inconsistent for all sociodemographic characteristics. Variation was observed only in the strength of the associations, not in their direction. However, due to unequal distribution of the individual behaviours, co-occurrence of unhealthy behaviours varied strongly across sociodemographic groups. CONCLUSIONS: Associations between health behaviours were relatively similar across sociodemographic groups. Since co-occurrence of unhealthy behaviours depends on the prevalence of individual unhealthy behaviours and the strength of their association, their co-occurrence in any particular sociodemographic group was primarily determined by the prevalence of individual unhealthy behaviours.

Adult↗

Not in their genes: phenotypic flexibility, behavioural traditions and cultural evolution in wild bonnet macaques.

Phenotypic flexibility, or the within-genotype, context-dependent, variation in behaviour expressed by single reproductively mature individuals during their lifetimes, often impart a selective advantage to organisms and profoundly influence their survival and reproduction. Another phenomenon apparently not under direct genetic control is behavioural inheritance whereby higher animals are able to acquire information from the behaviour of others by social learning, and, through their own modified behaviour, transmit such information between individuals and across generations. Behavioural information transfer of this nature thus represents another form of inheritance that operates in many animals in tandem with the more basic genetic system. This paper examines the impact that phenotypic flexibility, behavioural inheritance and socially transmitted cultural traditions may have in shaping the structure and dynamics of a primate society--that of the bonnet macaque (Macaca radiata), a primate species endemic to peninsular India. Three principal issues are considered: the role of phenotypic flexibility in shaping social behaviour, the occurrence of individual behavioural traits leading to the establishment of social traditions, and the appearance of cultural evolution amidst such social traditions. Although more prolonged observations are required, these initial findings suggest that phenotypic plasticity, behavioural inheritance and cultural traditions may be much more widespread among primates than have previously been assumed but may have escaped attention due to a preoccupation with genetic inheritance in zoological thinking.

Animals↗

Behavioural sensitization after repeated exposure to Delta 9-tetrahydrocannabinol and cross-sensitization with morphine.

RATIONALE: Repeated exposure to several drugs of abuse has been reported to induce behavioural sensitization. So far no evidence has been provided that such a phenomenon also applies to cannabinoids. OBJECTIVES: In this study we investigated if repeated exposure to Delta(9)-tetrahydrocannabinol (Delta(9)-THC) induces behavioural sensitization. In addition we tested the possibility of cross-sensitization between Delta(9)-THC and morphine. METHODS: Male Sprague-Dawley rats were administered for 3 days, twice daily, with increasing doses of Delta(9)-tetrahydrocannabinol (2, 4 and 8 mg/kg i.p.) or increasing doses of morphine (10, 20 and 40 mg/kg s.c.) or vehicle. After a washout of 14 days the animals were challenged with Delta(9)-THC (75 and 150 microg/kg i.v.), with a synthetic cannabinoid agonist WIN55212-2 (75 and 150 microg/kg i.v.) or with morphine (0.5 mg/kg i.v.), through a catheter inserted into the left femoral vein 24 h before, and the behaviour recorded. RESULTS: Rats previously administered with Delta(9)-THC showed a greater behavioural activation compared to controls in response to challenge with Delta(9)-THC (150 microg/kg i.v.) and to challenge with morphine (0.5 mg/kg i.v.). Similar to that observed after repeated opiates, this behavioural sensitization was characterized by stereotyped activity. Animals administered with a schedule of morphine that induces behavioural sensitization to morphine also showed a behavioural sensitization to challenge with cannabinoids (Delta(9)-HC and WIN55212-2, 75 and 150 microg/kg i.v.). The effect of the challenge with Delta(9)-THC was prevented by the administration of the CB1 antagonist SR141716A (1 mg/kg i.p.), 40 min beforehand. CONCLUSIONS: The results of the present study demonstrate that repeated exposure to Delta(9)-THC induces behavioural sensitization not only to cannabinoids but also to opiates. This cross-sensitization was symmetrical since rats behaviourally sensitized to morphine were also sensitized to cannabinoids. These observations further support the evidence of an interaction between the opioid and the cannabinoid system and might provide a neurobiological basis for a relationship between cannabis use and opiate abuse.

Analgesics, Non-Narcotic↗

Socio-economic differences in patterns of health and oral health behaviour in 25 year old Norwegians.

The purpose of this study was to test the hypothesis of multidimensionality of oral and general health behaviour. To evaluate the proposed behavioural dimensions, relationships with individual beliefs and socio-economic factors were explored. A simple random sample of 1190 residents born in 1972 was drawn from the populations of three counties in western Norway in February 1997. A questionnaire was mailed to the eligible sample. After one reminder, 735 subjects (58% women) replied. Principal component analysis (PCA) provided two factors, which accounted for 32.5% of the variance among the behavioural variables. One-way analysis of variance revealed significant, inverse relationships between two sum scores of health enhancing and health detrimental behaviour derived from the factors; socioeconomic variables and perceived vulnerability. Controlling for gender, multiple logistic regression analyses revealed significant relationships between health enhancing behaviour and occupational status (non-manual versus student, OR=0.6, 95% CI 0.4-0.8) and perceived vulnerability (OR=2.2, 95% CI 1.5-3.0). Occupational status (manual versus student OR=1.8 95% CI 1.2-2.6 and non-manual versus student OR=1.4 95% CI 1.0-2.1) turned out to be the strongest predictor of health detrimental behaviour. The present results indicate that oral and general health behaviour reflects two distinct behavioural domains. This appears to imply that oral and general health behaviour should be approached jointly in health promotion lifestyle programmes and that the lower socio-economic status groups should be targeted.

Adult↗

"Enough is enough, I don't want any audience": exploring medical students' explanations of consent-related behaviours.

Medical students are often faced with an ethical dilemma within the clinical setting--to learn from as many patients as possible but to learn only with consenting patients. Although studies have examined patients' and students' views about informed consent, none have examined how medical students talk about consent-related behaviours in 'naturalistic' focus group settings. This paper aims to explore medical students' explanations of behaviours relating to patient consent. Thirty-five excerpts across eight focus group discussions were identified using what we call momentum analysis: an identification of where the impetus of the groups' discussions changed noticeably. Ten were related to consent issues, seven of which occurred in focus groups with medical students. Utilising Malle's folk conceptual theory of behavioural explanation (2004. How the mind explains behavior. Folk explanations, meaning, and social interaction. Cambridge Massachusetts: MIT Press) within a narrative framework, we identified seven types of consent-related behaviour across the seven excerpts and 101 explanations for these behaviours by students. We found that students employed less reason explanations but more causal history reason (CHR) and enabling factor explanations than is found in other studies of naturally occurring talk, suggesting that consent-related behaviours were difficult and that our students actively managed others' impressions of them and their behaviours. Although our data is generally supportive of Malle's folk conceptual theory of behavioural explanation we suggest potential developments to this theoretical framework following our analysis with naturally occurring talk. However, further research is needed with larger samples of behavioural explanations to contribute more fully to theoretical development.

Adult↗

Effects of the benzodiazepine antagonist Ro 15-1788 on social and agonistic behaviour in male albino mice.

In view of recently reported low-dose behavioural activity of Ro 15-1788, the present study examined the effects of this benzodiazepine antagonist on social and agonistic behaviours in adult male albino mice. Using a resident-intruder paradigm, independent pharmacological manipulation of interactants and pharmaco-ethological analysis, our data demonstrate significant behavioural effects of Ro 15-1788 in benzodiazepine-naive animals. In residents, treatment with the antagonist (1.25, 2.5, 10 and 20 mg/kg, IP) resulted in dose-related increases in offensive threat behaviour and reduced olfactory investigation. However, 5 mg/kg exerted no detectable behavioural action in these animals. In intruders, behavioural effects were observed only with 1.25 mg/kg Ro 15-1788, and consisted of a profile suggestive of reduced defensiveness. In both experiments, the behaviour of untreated opponents confirmed the existence of drug-induced behavioural changes in their partners. It is argued that present data are not inconsistent with the existence of putative endogenous benzodiazepine-like ligands and that the differential effects of Ro 15-1788 in residents (singly-housed) and intruders (grouped) suggest one possible explanation for previous failures to detect low-dose behavioural activity with this compound.

Aggression↗

Role of dopaminergic system(s) in mediation of the behavioural effects of bombesin.

To test the effects of dopamine receptor blockade on bombesin (BN)-induced behavioural changes, adult male Sprague-Dawley rats were administered fluphenazine (0.01, 0.025, 0.1, 0.25 mg/kg, IP) followed 30 min later by BN (1 micrograms in 5 microliter) or saline (5 microliter) intracerebroventricularly (ICV). Subsequent behavioural effects were monitored in chambers equipped with strategically located infrared beam grids, controlled by a microprocessor. The following behaviours were monitored: locomotor activity (distance traversed), floor activity (horizontal or lateral displacement) and rearing activity (frequency of vertical displacement extending 17.8 cm above the floor). At all but the highest dose (0.25 mg/kg, which suppressed floor activity), fluphenazine failed to significantly alter any of the behavioural parameters monitored. Whereas at doses of 0.025 or lower, fluphenazine failed to alter BN-induced behavioural output, at doses of 0.1 mg/kg or greater, it significantly blocked the behavioural effects BN. In the next experiment, dopamine neurons of adult male Sprague-Dawley rats were lesioned using 6-hydroxydopamine (6-OHDA) (250 micrograms/10 microliter, ICV). The 6-OHDA and sham-lesioned (control) rats were administered BN (0.001, 0.01, 0.1 or 1.0 microgram, ICV) and their behaviour monitored. In the control animals, BN stimulated locomotor, floor and rearing activity in a dose-dependent manner. However, these behavioural effects of BN were markedly attenuated or absent in the 6-OHDA-lesioned animals. These data further support our contention that centrally administered BN may mediate its behavioural effects, through the dopaminergic system(s).

Animals↗

Ondansetron inhibits a behavioural consequence of withdrawing from drugs of abuse.

The ability of the selective 5-HT3 receptor antagonist ondansetron to influence the behavioural consequences of withdrawal from chronic treatment with ethanol, nicotine or cocaine was investigated in the light/dark exploration test in the mouse and social interaction test in the rat. In both tests acute and chronic (7 days) treatments with ondansetron (0.01-1.0 microgram.kg-1 IP) disinhibited suppressed behaviour; withdrawal from chronic treatment (0.1 mg/kg IP b.i.d.) did not exacerbate the behavioural suppression. Chronic treatment for 14 days with ethanol (8% w/v in the drinking water), nicotine (0.1 mg/kg b.i.d.) or cocaine (1.0 mg/kg b.i.d.) released suppressed behaviour in the mouse and rat tests. Behavioural suppression was increased following withdrawal from ethanol, nicotine and cocaine. The administration of ondansetron (0.01 mg/kg IP b.i.d.) during the period of ethanol, nicotine and cocaine withdrawal prevented the exacerbation in suppressed behaviour. It is concluded that ondansetron potently reduces behavioural suppression during acute and chronic treatments in the rodent models, does not cause a rebound exacerbation of behavioural suppression following withdrawal, and is a highly effective inhibitor of the increased behavioural suppression following withdrawal from the drugs of abuse: ethanol, nicotine and cocaine.

Animals↗

Differential effects of CGS 12066B and CP-94,253 on murine social and agonistic behaviour.

Although it has been previously proposed that 5-HT1B agonism specifically attenuates rodent agonistic behaviour, more recent investigations have indicated that such influences may be ancillary to an anxiogenic effect. The present study examined the influences of two 5-HT1B agonists, CGS 12066B and CP-94,253, on murine agonistic behaviour. In a resident-intruder paradigm, CGS 12066B (0.5-5.0 mg/kg) decreased resident offensive aggression, social interest, and exploration while dose-dependently enhancing defensive behaviours across the dose range tested. CP-94,253 (2.5-10.0 mg/kg) also reduced elements of resident offensive behaviour whereas defensive behaviours were largely unchanged. Some elements of resident nonsocial and social behaviour were enhanced at 2.5 and 5.0 mg/kg but decreased at 10.0 mg/kg. The behavioural profile of CP-94,253, but not CGS 12066B, supports the proposal that 5-HT1B receptors inhibit agonistic behaviour without concomitant sedative or anxiogenic effects. Findings are discussed in relation to 5-HT1A/1B/2C receptors involved in agonistic behaviour and anxiety.

Agonistic Behavior↗

Reactivity and repeatability of hygiene behaviour: structured observations from Burkina Faso.

If interventions promoting improved hygiene behaviour to prevent childhood diarrhoea are to be implemented and evaluated, valid methods for measuring this behaviour will be required. This paper presents findings from a study to investigate the use of structured observations to measure hygiene behaviour in Burkina Faso. Two hundred mothers with young children (2-36 months) were observed on several occasions, with particular attention focused on events/behaviour surrounding defaecation. Child defaecation occurred most often in a potty (67% of occasions). Stools were most often disposed of into a latrine (79%). Following defaecation the child's bottom was usually rinsed using water alone with a bare hand (76%). Subsequent hand washing by the mother/caretaker was much rarer (29%). None of these behaviours appeared "reactive" to the presence of the observer. Less common behaviors showed some evidence of reactivity. The frequency of child defaecation in the yard increased over the course of three observations (5% to 16%; P = 0.01) and the proportion of occasions on which the child was observed to be cleaned after defaecation declined (95% to 85%; P = 0.01). Mothers usually took with them to the latrine a water recipient (91%). Hand washing after leaving the latrine was observed on 30% of occasions. This proportion declined from 36% to 22% over three observations (P = 0.05). Defaecation by older siblings (aged 3-5 years) was usually into a potty (48%) or directly in a latrine (30%). There was no evidence that this behaviour was reactive. The repeatability of behaviours at the individual level was generally low. The site of index child defaecation (kappa = 0.27), how the child's bottom was cleaned (kappa = -0.01) and whether the caretaker washed her hands afterwards (kappa = 0.26) all showed low repeatability. The method of stool disposal was more repeatable (kappa = 0.73). Hand washing by mothers after using the latrine showed moderate repeatability (kappa = 0.40). Older sibling's defaecation behavior had excellent repeatability (kappa = 0.90). Our findings suggest that, in studies which aim to measure behaviour at the population level, structured observations may provide a useful tool. Studies which investigate links between hygiene behaviour and diarrhoea incidence at the individual level will require repeated observations of mothers and children since measuring behaviour during a single observation will lead to misclassification of exposure status, resulting in bias which could mask any underlying association. This is likely to be very costly.

Adult↗

Dopamine functions in appetitive and defensive behaviours.

The data reviewed here are compatible with the hypothesis that telencephalic dopamine activity is elicited by motivationally significant stimuli which in turn creates a neural state in which animals are more prepared to respond to significant stimuli in the environment. This analysis may be viewed as extensions of both the sensorimotor hypothesis, which depicts dopamine as potentiating the ability of stimuli to elicit responses (Clody and Carlton, 1980; Marshall et al., 1974; White, 1986) and of the incentive motivational hypothesis, which emphasizes the importance of dopamine in responding to stimuli that serve as signals of biologically significant events (Blackburn et al., 1989a; Crow, 1973; Mogenson and Phillips, 1976). In addition, we have sought to emphasize that not all responses are equally dependent upon the integrity of forebrain dopamine activity. Some responses, such as ingestion of standard foods by hungry animals, copulation, and escape, are relatively impervious to dopamine disruption. Further, once other behaviours, such as avoidance or appetitive operant responses, have been acquired, they can be maintained at an initially high rate despite perturbation of dopamine systems, although performance deteriorates with repeated testing. This analysis has emerged from the joint consideration of how both appetitive and defensive behaviours are influenced by dopamine antagonists, along with an examination of dopamine release during sequences of behaviour. The data reviewed suggest that dopamine is involved in fundamental psychological processes through which environmental stimuli come to exert control over certain aspects of behaviour. In the future, as knowledge in this field advances, there will have to be an integration of the literature on dopamine and motivation with the literature on dopamine and motor systems. We expect that dopamine release will be seen as a mechanism by which important environmental cues, of innate or learned significance, lead to a general enhancement of motor skeletal responses directed towards distal cues. We conclude with a caveat: Caution must be exercised when attempting to infer a general role of any neurotransmitter in motivated behaviour based on the study of a limited number of motivational systems. Although neurotransmitter pathways may figure prominently in the control of certain behaviours, it is incorrect to think of neurotransmitters as having a single role in behaviour. However, when comparative analyses reveal a common thread among different motivational systems, as is becoming apparent for the general role of mesotelencephalic dopamine pathways in behaviour, then the goal of generating coherent and comprehensive theory concerning a neurotransmitter's function in behaviour will begin to be realised.(ABSTRACT TRUNCATED AT 400 WORDS)

Aggression↗

Clinical assessment and interpretation of abnormal illness behaviour in low back pain.

Patients with chronic low back pain present with a mixture of symptoms and signs. Some are a direct consequence of physical pathology whereas others are attributable to associated and appropriate psychological and behavioural changes. At times the latter may be out of keeping with the degree of physical pathology and thus have specific significance in terms of the affective and cognitive disturbances that are also present and which may be the basis for abnormal illness behaviour. In an attempt to demonstrate more clearly the relationship between physical, psychological and behavioural components of illness, this paper draws on two data sets in patients with low back pain. The first explores the relationship between behavioural symptoms and signs, objective physical impairment, pain and disability and psychometric measures of distress together with scales making up the illness behaviour questionnaire (IBQ) of Pilowsky and Spence. A second data set is used to assess the value of the IBQ in understanding how psychological distress and behavioural signs and symptoms are related to the outcome of surgical treatment. The results gained reveal that behavioural symptoms and signs are directly related to the physical severity of low back disorder, the patient's report of pain and disability and the outcome of surgical treatment. Scores on the IBQ were strongly related to measures of affective disturbance and psychological distress. More specifically the disease affirmation scale of the IBQ, incorporating scales for disease conviction and psychological versus somatic focussing was an important dimension in relation to the behavioural symptoms and signs, thereby confirming results gained by other workers. Disease conviction and lack of response to clinicians' reassurances regarding illness - a situation in which abnormal illness behaviour is often deemed to exist - should not be seen simply as a function of the disease process, but more as a psychological coping mechanism for certain individuals under stress. The significance of this observation is discussed in relation to decisions regarding the overall assessment of chronic pain patients and their treatment.

Back Pain↗

The effects of simultaneous or separate infusions of some pro-opiomelanocortin-derived peptides (beta-endorphin, melanocyte stimulating hormone, and corticotrophin-like intermediate polypeptide) and their acetylated derivatives upon sexual and ingestive behaviour of male rats.

Intraneuronal post-translational cleavage of pro-opiomelanocortin yields a variety of peptides including beta-endorphin, melanocyte stimulating hormone and corticotrophin-like intermediate polypeptide, some of which are subsequently N-acetylated. Such peptides may be co-released from neuronal terminals, and so these experiments explored the effects of co-administration of some of them on sexual behaviour in the male rat, which is known to be sensitive to hypothalamic infusions of beta-endorphin. Peptides were infused into the pre-optic-anterior hypothalamic area bilaterally in doses up to 320 pmol, and males allowed access to a sexually receptive female and/or a sweet solution (0.1% Acesulfame-K) for 15 min, so that both sexual and ingestive behaviour could be studied. beta-Endorphin(1-31) by itself inhibited sexual interaction, confirming our previous data. Acesulfame-K ingestion was inhibited in control-infused rats in the presence of a female, but this inhibition was released when sexual behaviour was itself diminished by beta-endorphin(1-31). Both the acetylated and non-acetylated forms of melanocyte stimulating hormone (alpha-melanocyte stimulating hormone and des-acetyl melanocyte stimulating hormone) stimulate sexual behaviour; latencies both to ejaculation and to resumption of copulatory behaviour after an ejaculation (post-ejaculatory interval) were reduced. However, infusion of either corticotrophin-like intermediate peptide or N-acetylated beta-endorphin (1-31) had no effect on either sexual or ingestive behaviour. Infusion of either acetylated melanocyte stimulating hormone or des-acetyl melanocyte stimulating hormone mixed with beta-endorphin(1-31) prevented the inhibitory effect of the latter on sexual behaviour. Dose-response studies showed that the behavioural effect of such mixtures depended upon the molar ratios of the two peptides, rather than their absolute concentrations. The higher the ratio in favour of alpha-melanocyte stimulating hormone or des-acetyl melanocyte stimulating hormone, the greater the display of sexual behaviour. Infusing either corticotrophin-like intermediate polypeptides or N-acetyl beta-endorphin(1-31) with beta-endorphin(1-31) did not prevent the inhibition of sexual activity expected with beta-endorphin(1-31) alone. These results are discussed in terms of the functional consequences of co-release of proopiomelanocortin peptides from hypothalamic nerve terminals.

Acetylation↗

Specific effects of beta-endorphin infused into the amygdala on sexual behaviour in the male rat.

Bilateral intra-amygdaloid infusions of 0, 20, 60, 120 and 200 pmol beta-endorphin were administered to sexually experienced male rats in a Latin-square design. Sixty, 120 and 200 pmol beta-endorphin significantly decreased preintromission investigation rate and increased intromission latency with an oestrous female. No other effects on the male rats' sexual behaviour were produced. beta-Endorphin-induced effects on preintromission investigation and intromission latency were naloxone reversible (5 mg/kg, i.p.). Similar doses of intra-amygdaloid beta-endorphin had no effect on aggressive interaction with another, strange, male behaviour and similar doses of intra-amygdaloid corticotropin-releasing factor had no effect on sexual behaviour. Thus, there was both behavioural and chemical specificity of intra-amygdaloid beta-endorphin-induced effects on male sexual behaviour. Bilateral 60 pmol beta-endorphin infusions into the caudate-putamen had no effects on male sexual behaviour, demonstrating anatomical specificity of the intra-amygdaloid-induced effects. Basolateral excitotoxic lesions did not prevent the behavioural effects of intra-amygdaloid beta-endorphin infusions. These results demonstrate that intra-amygdaloid beta-endorphin specifically suppresses the precopulatory phase of male rat sexual behaviour but leaves the execution of the copulatory series intact once it has been initiated. This effect appears to be mediated via the corticomedial amygdaloid region. The change in precopulatory behaviour suggests that beta-endorphin may interfere with the processing of sensory information from the female, thus delaying appropriate initiation of the copulatory series.

Aggression↗