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PubMed2001

Effects of serotonin and serotonin analogs on posture and agonistic behavior in crayfish.

Exogenous serotonin has been shown to induce an elevated, flexed posture in crustaceans and has also been hypothesized to enhance aggressive behavior. We conducted three experiments to further investigate the effects of serotonin and serotonin analogs on posture and agonistic behavior in the crayfish Procambarus clarkii. In the first experiment, we recorded behavioral responses to five different concentrations of serotonin injected into the ventral hemolymph sinus. The amine elicited a series of behaviors including the characteristic high, flexed posture, but none were clearly associated with aggression. In our second experiment, we tested serotonin and four serotonin receptor agonists [1-(3-chlorophenyl)piperazine dihydrochloride, 2-methyl-5-hydroxytryptamine maleate, 5-carboxamidotryptamine maleate and alpha-methyl-5-hydroxytryptamine maleate] and measured the ability of each agonist to mimic the actions of the amine. High concentrations of 1-(3-chlorophenyl)piperazine dihydrochloride most closely mimicked the actions of serotonin; 5-carboxamidotryptamine maleate induced a high stance, but did not otherwise induce effects similar to serotonin. In our third experiment, we conducted an analysis of fighting behavior between pairs of crayfish that had received injections of control saline, serotonin, or 5-carboxamidotryptamine maleate. Serotonin generally reduced the level of aggression between opponents, whereas 5-carboxamidotryptamine maleate enhanced the performance of several agonistic behaviors.

Agonistic Behavior↗
PubMed2000

Similarities and differences in activities and agonistic behavior of male Eastern grey kangaroos (Macropus giganteus) in captivity and the wild.

The behavior of free-ranging and captive Eastern grey kangaroos Macropus giganteus, was observed by the same observers, with similar methods and under similar vegetational/climatic conditions in a 4.2-ha enclosure at Neuwied Zoo, Germany and at Grampians National Park, Victoria, Australia. Data were collected from a zoo group of 56 animals and a free-ranging mob of 50 to 60 animals. Males were individually identified and observed: 3 large males, 9 medium males, and 10 small males in the zoo, and 8 large, 9 medium, and approximately 10 small males in the National Park were present. Activities in both situations were very similarly distributed: Feed took up less time in the zoo, resting was almost similar in both situations, alert behavior was significantly different for small and medium males, locomotor activities were similar in large males and females, autogrooming occurred significantly more in the zoo only for females. Frequencies of social interactions were slightly greater for large males and females in the zoo. Agonistic behavior in males was more frequent in the zoo situation, except for ritualized fights. Sequences of agonistic behavior were more predictable in the zoo. No differences in escalation tendencies toward potentially injurious fighting could be found. Zoo Biol 19:529-539, 2000. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗
PubMedDate not supplied

Agonistic behavior: a model, experimental studies, and perspectives.

Agonistic (competitive) behavior includes the manifestations of aggression and submissiveness by individuals in conflict situations and is a universal form of behavior found in animals of different species. The sensory contact model allows aggressive and submissive (inhibited, suppressed) types of behavior to be formed in male mice as a result of acquisition of repeated experience of social conquests or defeats in daily aggressive interactions. Chronic experience of aggression is accompanied by total activation of the dopaminergic systems in the victors. At the same time, experience of social defeat leads to changes in the state of the serotoninergic and noradrenergic systems of various parts of the brains of the defeated animals. As a consequence, significant differences in emotional expression, movement activity, investigative activity, communicative ability, alcohol consumption, and many physiological aspects were found in animals of opposite social groups. The extent and nature of these changes depended on the type of social behavior formed by the animals (victors, vanquished), the duration of confrontational experience, and the genetically determined characteristics of the animals (i.e., which line of mice). The possibilities and perspectives of this model of sensory contact in medical-biological and basic investigations is discussed.

Agonistic Behavior↗
PubMed2001

Agonistic behavior in naïve juvenile lobsters depleted of serotonin 5,7-dihydroxytryptamine.

We have been exploring the role of serotonin in fighting behavior in lobsters using a specific model of agonistic behavior, the establishment of hierarchical relationships between pairs of socially naive juvenile lobsters. We selected this model because the behavior is easily evoked, readily quantifiable, and the effects of experience are eleminated by using socially naive animals. In these studies we injected a specific neurotoxin, 5,7-dihydroxytryptamine, into juvenile lobsters over a 4-week period and then measured the effects on fighting behavior. This treatment reduces the levels of serotonin in the nervous system and immunocytochemical studies show a dramatic reduction in neuropil staining for the amine. Control animals received vehicle injection alone. All injected animals were paired against larger or smaller non-injected opponents, and three successive 30-min fights were carried out and statistically analyzed. The results were surprising: As with elevations of serotonin, reduced levels of serotonin increased the amount of time animals engaged in fighting behavior. No significant effects were seen on who initiated encounters, who retreated first, or who the eventual winner would be. Thus, in this model, elevation or reduction of serotonergic function increases the tendency of animals to engage in agonistic encounters.

5,7-Dihydroxytryptamine↗
PubMed1994

Agonistic behavior, plasma stress hormones, and metabolites in response to dyadic encounters in domestic pigs: interrelationships and effect of dominance status.

Agonistic behavior, neuroendocrine, and plasma metabolite changes were studied in 16 domestic Large White pigs (100 +/- 5 kg) submitted to dyadic encounters (30 min) in a neutral environment. The animals had been housed individually for 2 months prior to the experiment. Aggressive and submissive behaviors were recorded for each animal during the encounter. Surgically implanted catheters allowed collection of blood samples at selected times. Plasma levels of cortisol, catecholamines, and metabolites were determined and compared with data obtained on eight control pigs kept under resting conditions. Resting plasma cortisol levels tended to be higher in subordinate compared to dominant subjects, suggesting a relationship between baseline adrenocortical activity and submissive behavior during aggressive encounters in domestic pigs. Plasma norepinephrine and epinephrine levels did not differ between dominants and subordinates, but they were linearly correlated with aggressive behaviors. Metabolic state changed in response to the encounters, as evidenced by increased plasma levels of free fatty acids, glucose, and lactate at the end of the dyads. Dominance status did not significantly affect plasma metabolite levels. Plasma lactate and glucose levels were linearly correlated with both aggressive behaviors and plasma catecholamines. The present results provide evidence suggesting that stimulation of the sympathetic nervous system and physical activity are both involved in the control of the mobilization of body energy sources in response to aggressive encounters in domestic pigs.

Aggression↗
PubMed1983

[Pharmaco-ethological analysis of agonistic behavior between resident and intruder mice: effects of ethylalcohol].

The present study was conducted to investigate the effect of ethylalcohol on agonistic behavior using a resident-intruder paradigm. In this paradigm, a resident male mouse has been cohabiting with a female for 5 weeks, and an intruder male mouse is introduced into the resident's home cage. The effects of four doses of ethylalcohol (vehicle, 0.5, 1.0, and 2.0 g/kg, p.o.) were assessed in resident mice and group-housed intruder mice. Residents and intruders were drugged on alternate test days, and all animals received different sequences of drug conditions according to a random schedule. When resident mice were treated with ethylalcohol biphasic effects on resident's aggressive elements were observed: 0.5 and 1.0 g/kg of ethylalcohol increased attack bitings and sideways posture, while 2.0 g/kg of the drug suppressed aggressive elements. On the other hand, when intruder mice were drugged the resident's attack bitings were significantly increased in a dose-dependent manner. At this time, defensive upright postures of intruder mice were suppressed by the drug. Ethylalcohol at the employed doses did not affect locomotor activity in both resident and intruder mice. The results suggest that ethylalcohol enhances the hostility of resident to the intruding animal and suppresses the anxiety of an intruder to the attacking animal.

Aggression↗
PubMed1984

[Pharmaco-ethological analysis of agonistic behavior between resident and intruder mice: effects of psychotropic drugs].

The present study was conducted to investigate the effects of psychotropic drugs on agonistic behavior between resident and intruder mice. The effects of four doses of the following drugs were assessed in either resident or group-housed intruder mice: chlordiazepoxide (0, 5, 10 and 20 mg/kg, i.p.), haloperidol (0, 0.25, 0.50 and 0.75 mg/kg, i.p.) and imipramine (0, 5, 10 and 20 mg/kg, i.p.). Residents and intruders were drugged on alternate test days, and all animals received different sequences of each of the drug conditions according to a random schedule. The injection-test interval was 30 min. When resident mice were treated with chlordiazepoxide the resident's aggressive episodes (sideways posture, attack bite, tail rattle) were significantly suppressed. Both haloperidol and imipramine also showed a similar suppressive effect on the resident's aggressive episodes, but haloperidol significantly suppressed locomotor activity at all doses. When intruder mice were treated with chlordiazepoxide, attack bites by untreated residents were significantly increased in a dose-dependent manner, and the frequency of defensive upright posture displayed by intruder animals were significantly decreased. Haloperidol and imipramine did not alter resident's behavior and intruder's upright posture when intruders were drugged. The results suggest that chlordiazepoxide has specific effects on both the hostility of the resident and the anxiety of the intruder, differing from haloperidol and imipramine.

Aggression↗
PubMed1978

Agonistic behavior elicited by electrical stimulation of the brain in western collared lizards, Crotaphytus collaris.

Western collared lizards, Crotaphytus collaris, were tested in three experiments using electrical stimulation of the brain. In experiment 1, agonistic behavior (defensive, aggressive and escape) responses were elicited in free-moving unanesthetized lizards. In experiment 2, areas were localized from which gular extension, a common component of defensive and aggressive behavior, could be evoked in anesthetized animals. Experiment 3 was carried out to demonstrate that defensive and aggressive behavior could be elicited from the same stimulation sites both in anesthetized and unanesthetized lizards. Initially, gular extension was evoked while the animal was anesthetized and later the animal was tested while freely moving and unanesthetized. Based on a combined plot of the sites from which defensive and aggressive behavior was evoked in experiments 1--3, the higher threshold sites (51--750 muA) were in the dorsal ventricular ridge anterior, amygdaloid complex, septal and preoptic areas, hypothalamus, thalamus and adjacent to the nucleus profundus mesencephali (NPM) and reticular formation. Lower threshold sites (up to 50 muA) are found in the NPM and the reticular formation. Escape behavior can be evoked from stimulation sites within or adjacent to areas from which defensive and aggressive behavior can be elicited.

Aggression↗
PubMed1993

Effects of (-)-pindolol and SDZ 216-525 on social and agonistic behavior in mice.

In view of conflicting results reported for 5-HT1A receptor involvement in murine social conflict, this study examined the effect of two compounds, SDZ 216-525 and (-)-pindolol, on agonistic and social behavior in male mice. In a resident-intruder paradigm, (-)-pindolol (1.0-20.0 mg/kg), a beta-adrenergic 5-HT1A/1B antagonist, significantly attenuated all agonistic behaviors across the dose range employed. Social behaviors showed significant decreases, while nonsocial cage exploration showed significant increases at all doses. Defensive evade was significantly attenuated at 20.0 mg/kg. SDZ 216-525 (0.025-1.0 mg/kg), a selective 5-HT1A antagonist, significantly attenuated offensive posturing and bite-attacks at 1.0 mg/kg, and all offensive behaviors nonsignificantly at the smaller doses tested. Rearing was significantly attenuated at 1.0 mg/kg, while cage exploration increased at this dose. Defensive and social behaviors remained largely unchanged. These results show that both compounds tested produced significant reductions in offensive behavior, with concomitant changes in defensive, social, and nonsocial behaviors. Results are discussed in relation to SDZ 216-525 and (-)-pindolol potential for the control of anxiety and agonistic behavior.

Agonistic Behavior↗
PubMed1989

Influence of the mesocortical dopaminergic system on activity, food hoarding, social-agonistic behavior, and spatial delayed alternation in male rats.

In order to assess the behavioral role of the dopaminergic mesocortical input to the prefrontal cortex, bilateral lesions were made in the ventral tegmental area (VTA). The possibility of a functional recovery by the administration of a dopamine agonist was examined. General activity, food hoarding, social-agonistic behavior, and spatial delayed alternation performance were recorded in rats with VTA lesions and in sham-operated animals. In the open field animals with VTA lesions were more active but showed less anxiety. Food hoarding was impaired. In dyadic interactions with sham-operated opponents, VTA rats were socially more active, whereas sham operates performed more keeping down and aggressive grooming. This behavioral deficit was partially recovered when apomorphine was administered prior to testing. VTA animals were impaired in the performance of a spatial delayed alternation task with an intertrial interval of 15 s, whereas no impairment was found with a 0-s intertrial interval. The theoretical implications of these findings are discussed.

Aggression↗
PubMed1986

Agonistic behavior patterns in mice with streptozotocin-induced diabetes mellitus.

To examine the effects of the altered metabolic and hormonal state of diabetes mellitus on rodent social behavior, male Swiss Webster mice made diabetic with streptozotocin were tested in a resident-intruder encounter. Isolated diabetic and control mice were introduced as intruders into the home cages of aggression-trained resident mice. The encounters were videotaped and analyzed for frequencies and durations of agonistic behavior. Diabetic mice responded to the aggression of resident mice with significantly less investigation and aggression and significantly more static defense and escape behaviors than did control mice. Resident mice responded to less aggressive diabetic mice with more aggression and social investigation. Plasma corticosterone levels were significantly higher in diabetic mice compared to controls and positively correlated with submissive behavior in diabetic mice. These findings indicate that social behavior is altered in male diabetic mice and support the hypothesis that elevated pituitary-adrenal cortical activity and/or metabolic changes affect behavior in male diabetic mice.

Aggression↗
PubMedDate not supplied

Agonistic behavior during stress prevents the development of learned helplessness in rats.

Male Wistar rats were subjected to unavoidable electrical pain stimulation either in individual cages or in pairs. During the procedure, rats stressed in pairs fought. After 48 h, rats were tested in a shuttle box for the ability to develop active avoidance responses. The proportion of escape and avoidance responses was significantly lower in rats stressed individually as compared with intact animals and animals stressed in pairs. Plasma corticosterone was assayed one day later, at rest and after dexamethasone administration. There were no significant differences in resting corticosterone level between groups of animals. Administration of dexamethasone significantly reduced the plasma corticosterone level in intact rats and in animals stressed in pairs, but not in rats stressed individually. Thus, agonistic behavior during unavoidable stress prevents the development of pathological changes in adaptive behavior and the endocrine system.

Agonistic Behavior↗
PubMed1977

5,7-Dihydroxytryptamine lesions of the ascending 5-hydroxytryptamine pathways: habituation, motor activity and agonistic behavior.

Rats were injected stereotactically in mesencephalon with 5,7-dihydroxytryptamine (5,7-DHT) in the medial 5-hydroxytryptamine (5-HT) pathway (n = 8) and in the medial plus the lateral 5-HT pathways (n = 7) or injected with vehicle (n = 8), or sham-operated (n = 8). The 5,7-DHT lesions reduced the in vitro 3H-5-HT uptake in the hypothalamus and the cortex cerebri to 27-51% of control values, 3H-noradrenaline uptake was not significantly changed. 5,7-DHT lesions of the medial, and of the medial plus the lateral, 5-HT induced mouse killing behavior and increased number of boxing positions in the shock elicited fighting test. Both lesions also reduced the rate of habituation to touch, but only the lesion of the medial plus the lateral 5-HT pathway significantly reduced the rate of habituation to acoustic stimulation. Activity in the home cage was not significantly changed by the lesions. It was concluded that selective chemical lesions of the ascending 5-HT pathways result in prolonged habituation of the orienting response and increase in particular components of agonistic behavior. The increase in locomotor activity observed after electrolytic lesions of nucleus raphe medianus seems not to be due only to lesion of the 5-HT neurons ascending from this nucleus.

5,7-Dihydroxytryptamine↗
PubMed1986

Aerosolized 5 alpha-androst-16-en-3-one reduced agonistic behavior and temporarily improved performance of growing pigs.

Two experiments were conducted to determine the effect of aerosolized 5 alpha-androst-16-en-3-one (androstenone) on pig aggressive and submissive behaviors and on pig performance. In Exp. 1, twenty-four 5-wk-old pigs were randomly regrouped in a two-pig bioassay. A solution of either isopropyl alcohol or .5 mg androstenone in isopropyl alcohol per pig was aerosolized on both pigs in the observation pens. Summarization of video records from the 90-min bioassay showed that pens of pigs aerosolized with androstenone spent 58% less time engaged in aggressive behavior (P less than .05) and 96% less time engaged in submissive behavior (P less than .01). In Exp. 2, a performance trial was conducted with finishing pigs from 57 to 91 kg body weight. Factorially arranged treatments included aerosolized androstenone (.5 mg/pig) or the vehicle isopropyl alcohol and regrouping into uniform body weight blocks or no regrouping. Regrouping depressed average daily feed consumption (P less than .05) and average daily gain (P less than .05) for the first 7 d of the trial. Pigs reveiving the androstenone aerosol had improved average daily gain (P = .01) and gain:feed ratio (P less than .01) for the first 28 d of the trial. Performance of all treated pigs was similar for the entire finishing period. This olfactory stimulant reduced pig agonistic behavior and transiently improved performance of regrouped and non-regrouped finishing pigs.

Aerosols↗
PubMed1997

Annual cycle of plasma testosterone in male copperheads, Agkistrodon contortrix (Serpentes, Viperidae): relationship to timing of spermatogenesis, mating, and agonistic behavior.

Reproductive cycles of the majority of squamate reptiles remain undescribed. Few studies are available on seasonal patterns of circulating steroid hormones in snakes. The goal of this study was to document the annual cycle of plasma testosterone (T) in male copperheads Agkistrodon contortrix, a North American pitviper (Serpentes, Viperidae). Two experimental conditions were used in this laboratory study. One condition (repeat-test group) consisted of 10 adult males that were sampled once each month for 11 months. The other condition (single-test groups) consisted of 10 groups each with 5 males (N = 50), and each male was tested a single time. The single-test condition was used to evaluate whether or not repeated handling and sampling affected T levels. The study was conducted from February-December, 1992. A well-defined seasonal pattern of plasma T levels was detected; patterns were similar under both experimental conditions with the exception that the repeat-test group had slightly lower levels. Levels of T were lowest (baseline) in April-May, increased in early summer (June), and were highest in late summer (August). Thereafter, T levels declined up to the time of hibernation (early November) and changed little during hibernation (November-January). Upon emergence from hibernation in late winter (February), T levels increased sharply from February to March and then decreased from March to April. The results are discussed in the context of timing of spermatogenesis, mating, and male agonistic behavior.

Agkistrodon↗
PubMed2003

Stress and the development of agonistic behavior in golden hamsters.

Aggressive behavior can be studied as either offensive or defensive responses to a stimulus. The studies discussed in this review are focused on the peripubertal development of offensive aggression in male golden hamsters and its responsiveness to repeated social stress. Quantitative and qualitative changes in offensive responses were analyzed during this period. Quantitative changes in offensive responses were observed as decreased frequency of attacks. Qualitative changes were observed as changes in attack types, as animals reorient their attacks gradually from the face to the lower belly and rump. These developmental changes were altered by repeated exposure to social stress during early puberty. Daily exposure to aggressive adults during early puberty accelerated the qualitative development of offensive responses and the onset of adult-like offensive responses. In contrast, social stress had little effect on the quantitative changes associated with early puberty. However, social stress was associated with higher attack frequency during adulthood. These effects of stress during early puberty contrast with those observed with animals in late puberty. At that time, repeated exposure to aggressive adults inhibits offensive aggression. These data constitute the basis for a new theory on the development of agonistic behavior that includes the following hypotheses. First, it is hypothesized that mid-puberty is marked by a change in responsiveness to repeated social stress. As such, differences in stress responsiveness from social interactions are interpreted as a basic distinction between play fighting and adult aggression. Second, it is also hypothesized that a common neural circuitry mediates the activation of offensive responses during play fighting and adult aggressive interactions.

Agonistic Behavior↗
PubMed1988

Effects of photoperiod, the pineal gland and the gonads on agonistic behavior in female golden hamsters (Mesocricetus auratus).

Four studies were conducted to determine the role of photoperiod, the pineal gland and the gonads in the regulation of intrasex agonistic behavior in female hamsters. In the first experiment animals maintained under Long or Short photoperiods were tested in same or opposite photoperiod pairs. Under both testing conditions, Short-day animals tended to exhibit a higher ratio of offensive to defensive behaviors, which was due primarily to a reduced level of defensive behavior in Short-day groups. In the second experiment animals under Long and Short photoperiods were tested following sham surgery or pinealectomy. Short-day sham animals exhibited the highest level of offensive behavior, the lowest level of defensive behaviors and the highest offensive/defensive ratio; pinealectomy eliminated the Short-day advantage. In the third experiment, Long-day animals receiving exogenous melatonin showed a higher level of agonistic responding than animals injected with control vehicle, indicating that Short-day effects are probably mediated through pineal melatonin. The results of the last experiment in which ovariectomy to Long-day animals was not able to mimic the effects of photoperiod or exogenous melatonin indicated that the photoperiod effects on aggression are probably not mediated through the gonads.

Aggression↗
PubMed1994

5-HT1A receptor influences on rodent social and agonistic behavior: a review and empirical study.

Investigations examining the influence of 5-HT1A receptors in murine agonistic and social behavior have reported either specific or nonspecific attenuation of offensive behavior. To clarify this situation, the effects of three 5-HT1A agonists were examined on isolation-induced aggression and social behavior in male mice. 8-OH-DPAT (0.025-1.25 mg/kg) increased social behavior, rearing, and digging. Offensive behavior was reduced, without concomitant sedation. Ipsapirone (0.1-10.0 mg/kg) reduced naso-nasal behavior, whilst enhancing stretched-attend behavior, cage-exploration, and rearing. Offensive and defensive behaviors were attenuated, without reductions in activity. MDL 73005 EF (0.25-8.0 mg/kg) reduced social behaviors, cage-exploration and rearing while maintenance behavior was increased. Offensive and defensive behaviors showed attenuation. Current results corroborate previous findings with respect to 5-HT1A receptor involvement in murine agonistic behavior and anxiety. Data also connote that the behavioral specificity of 5-HT1A ligands should be interpreted in terms of response competition rather than solely concomitant sedation.

8-Hydroxy-2-(di-n-propylamino)tetralin↗