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PubMedDate not supplied

The effects of NPY and 5-TG on responding to cues for fats and carbohydrates.

Previous research has shown that glucoprivic and lipoprivic metabolic challenges selectively augment the performance of appetitive responses conditioned to carbohydrate- and fat-associated cues, respectively. The present experiment investigated whether intracerebroventricular (i.c.v.) infusion of neuropeptide Y (NPY) has a similar selective effect on appetitive behavior. We trained rats to associate two different conditioned stimuli (CSs) with two different macronutrient (peanut oil and sucrose pellets) unconditioned stimuli (USs). After training, the rats were food sated and responding to each CS was then tested in extinction. In one test session, the effects of NPY were compared to isotonic saline. A second test compared the effects of these two treatments with i.c.v. infusion of the glucose antimetabolite 5-thio-d-glucose (5-TG). Replicating our earlier result, 5-TG selectively promoted conditioned responding to the CS for sucrose pellets. In contrast, the capacity of NPY to promote appetitive behavior did not depend on the macronutrient that was signaled by the CS. These results suggest that NPY and 5-TG promote appetitive behavior via different mechanisms.

Animals↗
PubMed2006

Environmental enrichment reduces impulsivity during appetitive conditioning.

Although environmental enrichment is presumed to enhance learning, appetitive behavior may also be altered by this experience: anticipatory responding for sucrose is reduced in environmentally enriched (EE) rats [van der Harst, J.E., Baars, A.M. and Spruijt, B.M. Standard housed rats are more sensitive to rewards than enriched housed rats as reflected by their anticipatory behaviour. Behav Brain Res 2003;142:151-156]. To assess the impact of differential environmental experience on learning and appetitive behavior, we trained 17 EE and socially isolated (SI) rats in a three-phase, operant-shaping procedure for sucrose reinforcement. In phase one, a feeder cue was paired with sucrose availability. In phase two, a nose poke to either one of two lit holes on the opposing wall activated the feeder cue. In phase three, the feeder cue was elicited by a poke to a single lit hole. While acquisition rates in phase one and phase two were similar, EE animals reached phase-three criteria [completion of 100 trials in 45 min and 15 or fewer bad pokes] faster than SI animals. These two groups showed similar session completion rates, reinforced and non-reinforced licking responses, and overall behavioral activity during phase three acquisition; however, SI rats performed more bad pokes (responses to the non-lit hole after nose-poke cue onset) and intertrial interval (ITI) pokes during this training period. Because all ITI (and presumably many bad) pokes were initiated before onset of nose-poke cue, this difference indicates greater anticipatory responding in SI animals. This experience-dependent alteration in appetitive behavior may explain, in part, the tendency of SI rats to show attenuated learning rates in appetitive contexts in which complex contingencies exist.

Animals↗
PubMed1991

Chronic administration of flumazenil (Ro 15-1788) enhances non-appetitive exploratory behavior of rats.

The effects of chronic administration of the benzodiazepine receptor antagonist, flumazenil (Ro 15-1788; 4 mg/kg/day for 14 days in drinking water) on the performance of adult rats in the 12-arm radial maze were studied. Relative to controls, the animals treated with flumazenil showed an increase (P less than 0.002) in non-appetitively motived exploratory behavior, so called because it occurred in 88% of instances in non-baited alleys, facing the well-illuminated "enriched environment" of the center of the room, as opposed to the baited alleys, facing the "dull" corner of the room. This behavior emerged between day 5 and 7 of treatment with the drug, it continued to increase over the period of treatment with drug (P less than 0.002), and reached its peak at day 3, after withdrawal of the drug (P less than 0.008; a longer duration was not investigated). The occurrence of non-appetitively motivated exploratory behavior was inversely correlated with the scores for urination/defecation (P less than 0.003) and, therefore, most likely reflected the anxiolytic action of flumazenil. During treatment with drug or vehicle, the control and the drug groups made comparable numbers of "working memory" errors (P = 0.17). However, upon withdrawal of drug and introduction of alley gates (to confine the animal for 10 sec to the center platform, after an alley was explored), the working memory errors of the rats exposed to the drug, remained unchanged (P = 0.35), relative to the preceding three trials, while the performance of the control group was disrupted, as shown by an increase in the numbers of errors (P less than 0.004). At day seven of treatment with drug, the emergence of exploratory behavior was associated with an increased density and/or affinity of benzodiazepine receptors in cortex, hippocampus and brain stem, while three days after withdrawal of drug, when the exploratory behavior reached its peak, there was a reduction in GABA-enhanced binding of [3H]flunitrazepam in the cortex.

Animals↗
PubMed1975

The effects of mevinphos on appetitive operant behavior in the gerbil.

The need for study of the effects on performance of non-lethal organophosphate insecticide exposure is founded on many reports of behavioral difficulties in aerial applicators following exposure. In this study, a different pair of gerbils served in each of the following schedules of reinforcement: FR 25, FR 75, DRL 12-sec, DRL 20-sec, and VI 1-min. Baseline performance in these tasks tended to be comparable to that of more common laboratory species, but was more variable in the case of the VI 1-min task. Mevinphos doses of 0.20 mg/kg and above produced observable somatic signs of poisoning and also produced dose-related decrements in performance in FR and VI tasks. Performance in the DRL schedule was affected only at a dose of 0.30 mg/kg. No performance deficits or overt somatic signs of poisoning were present at mevinphos doses of 0.10 mg/kg or lower. These results do not agree with those of an earlier study which decrements in VI performance of pigeons and squirrel monkeys appeared at low mevinphos doses which did not produce overt somatic signs of poisoning. The possibility of variations in mevinphos effect as a function of species and task was discussed.

Animals↗
PubMed1996

Appetitive sexual behavior in male rats: 1. The role of olfaction in level-changing behavior.

Level-changing behavior is a form of anticipatory behavior of a male rat, when tested in a bilevel testbox. The male explores the testcage prior to introduction of a female. The female is introduced after 5 min. The number of level changes displayed by the male in this period reflects appetitive aspects of sexual behavior and it was suggested that analysis of this level-changing behavior may function as assessment of sexual motivation. In this study the increase of anticipatory level changes over repeated weekly tests was dependent upon (sexual) olfactory stimulation. The number of anticipatory level changes was reliably reduced by administration of the opioid antagonist naloxone, suggesting that endogenous opioids facilitate this behavior. These results suggest that the increase of anticipatory level changes over repeated tests is a response to olfactory stimuli and reflects appetitive aspects of sexual behavior, which are stimulated by endogenous opioids. These results are in accordance with the concept that analysis of anticipatory level-changing behavior can be used to assess sexual motivation.

Animals↗
PubMed1998

A peptidergic basis for sexual behavior in mammals.

Vasopressin (VP) is a peptide neurotransmitter in the limbic system of rats. It is synthesized in the medial amygdaloid nucleus in the presence of sex steroids, transported to other limbic structures such as the hippocampus and septum and secreted there by a calcium-dependent process. In the hippocampus, VP acts on cerebral microvessels and local circuit interneurons. Its excitatory action on the inhibitory interneurons produces near-total shutdown of electrical activity of the efferent fibers of pyramidal cells, the projection neurons of the hippocampus. Stimulation of the medial amygdala and release of the endogenous VP duplicates these effects and, since they are blocked by ventricular application of a VP antagonist, the effects are almost certainly mediated by endogenous VP. Recording from the VP-containing cell bodies or of the hippocampal action of the peptide indicates that the system is selectively involved with the early stages of sexual behavior, specifically those appetitive behaviors that anticipate coitus. Stimulation of the VP cells produces alterations in sexual behavior in a manner consistent with the hypothesis that the medial amygdala organizes the appetitive phase of recognition of an appropriate partner and sexual arousal. This role for the medial amygdala complements the proposed role of nearby structures in the consummatory, reward and learned aspects of sexual behavior. Association between VP, oxytocin (OT) and homologs with sexual behavior is very widespread among vertebrates, including amphibians, reptiles, primates and humans. Humans and other primates display a phenomenon called 'concealed ovulation' that may have played a role in the evolution of social structures. The review concludes with a discussion of possible experimental strategies for evaluating the possible role of VP in concealed ovulation and other conditions in which sexual behavior occurs outside of estrus.

Animals↗
PubMed2006

Mood disorders in intellectual disability.

PURPOSE OF REVIEW: This article examines reviews and research on the diagnosis and treatment of mood disorders in people with intellectual disability published from September 2004 to December 2005. RECENT FINDINGS: Patients with intellectual disability have limitations in verbal ability, and with increasing levels of disability may have an atypical clinical presentation. Thus, methods to diagnose mood disorders were a major research focus. Informant-rating scales and two self-report instruments provided data on thought patterns, aberrant behavior, appetite, and suicidality. Behavioral symptoms such as aggression were frequently associated with mood disorders. Pharmacotherapy and electroconvulsive therapy were found to be effective treatments. Mood disorders were frequently identified in people with intellectual disability, although suicide was still quite rare. SUMMARY: Patients with milder levels of disability can use self-report measures and can be diagnosed using standard criteria with little modification. For those with more severe disability, diagnosis is challenging and often requires the use of residual categories. Atypical clinical presentation, including maladaptive behaviors, lent support for 'behavioral equivalent' substitutes of standard criteria. Typical pharmacological agents were effective for depression and electroconvulsive therapy for treatment-resistant bipolar disorder.

Aggression↗
PubMed1989

[Physalaemin-like N-terminal fragments of mammalian tissues, PHLIP-7 and PHLIP-8 do not modify drinking behavior and sodium appetite in rats].

PHLIP-7 and PHLIP-8, two peptides reproducing at least in part the N-terminal aminoacid sequence of physalaemin, have been identified in mammalian tissues. These peptides produce alterations of fighting behaviour in the mouse, but are devoid of any behavioural activity in the rat. This suggests that PHLIP-7 and PHLIP-8 have no affinity for brain receptors involved in the behavioural effects evoked by tachykinins in the rat, and that the brain of this animal is lacking in receptors for the N-terminal sequence of tachykinins.

Amino Acid Sequence↗
PubMed2003

Sardinian alcohol-preferring and non-preferring rats show different reactivity to aversive stimuli and a similar response to a natural reward.

Sardinian alcohol-preferring (sP) and non-preferring (sNP) rats were studied to ascertain whether some behavioral and/or neurochemical traits, beyond ethanol preference, differentiated the two lines. Spontaneous reactivity of Wistar, sP and sNP rats to aversive or pleasurable stimuli was examined in an avoidance test, an elevated plus maze test, and in response to palatable food presentation. As the mesocorticolimbic dopaminergic system plays a relevant role in the response to rewarding or aversive stimuli, extraneuronal dopamine levels and cocaine-induced dopamine accumulation in the nucleus accumbens shell (NAcS) and medial prefrontal cortex (mPFC) were studied by microdialysis in the three groups of rats. Moreover, rats were exposed to repeated unavoidable stress and their avoidance response and NAcS dopamine output were determined. Finally, the capacity of sP, sNP, and Wistar rats to learn a palatable food-sustained appetitive behavior was studied. The present study shows that, beyond ethanol preference, there are several behavioral and neurochemical distinctions between sP and sNP rats. The sP rats displayed an increased level of anxiety-like behavior and sNP rats showed a reduced avoidance of noxious stimuli, compared to Wistar rats. Moreover, in the NAcS and PFC, extraneuronal dopamine levels were higher in sP rats and lower in sNP rats compared to Wistar rats; cocaine-induced dopamine accumulation in the NAcS was higher in sP rats than in sNP and Wistar rats. However, sP and sNP rats showed a similar behavioral and neurochemical response to chronic unavoidable stress. Interestingly, they also showed similar behavioral and neurochemical responses to a natural rewarding stimulus and a similar ability to learn an appetitive behavior.

Alcohol Drinking↗
PubMed1991

Effects of stimulus intensity and quality on discrimination of odorant mixtures by spiny lobsters in an associative learning paradigm.

The Florida spiny lobster, Panulirus argus, can behaviorally discriminate between members of a set of four artificial odorant mixture types: crab, mullet, oyster, and shrimp. The present experiments were designed to examine the effects of both intensity and quality on discrimination of odorant mixtures. This was accomplished by conditioning lobsters to only one concentration (0.5 mM) of shrimp mixture and testing them with four concentrations (0.005, 0.05, 0.5 and 5.0 mM) of shrimp mixture and two concentrations (0.05 and 0.5 mM) of oyster mixture. For the two appetitive behaviors examined, lobsters did not discriminate the conditioned mixture (0.5 mM shrimp) from any other of the same-type nonconditioned mixtures. For a third behavior, active avoidance, lobsters discriminated, to a significant degree, the 0.5 mM shrimp mixture from all of the nonconditioned mixtures. However, aversion values for the nonconditioned shrimp mixtures were markedly and consistently higher than those for the nonconditioned oyster mixtures for all three behaviors. Thus, when spiny lobsters are forced to use intensity as a cue (as in an aversive conditioning situation), they have the ability to discriminate between mixtures of the same quality but different intensity. Nevertheless, based on examination of post-conditioning decreases in appetitive behaviors, it is most likely that the intensity of an odorant mixture has a relatively minor effect on the discrimination of the quality of that mixture by these animals, at least over a 1000-fold concentration range.

Animals↗
PubMed2000

Dehydroepiandrosterone-mediated decrease in caloric intake by obese Zucker rats is not due to changes in serum entrostatin-like immunoreactivity.

To understand the mechanism(s) of appetite modulation by DHEA, we have undertaken a series of studies to examine the effects of DHEA on neurotransmitters and neuropeptides known to affect appetitive behavior. Here, we report the effect of DHEA on serum enterostatin-VPDPR or E, a pentapeptide known to cause selective diminution in fat intake. Four-week-old lean (fa/+) and obese (fa/fa) Zucker rats were divided into control and treatment groups. DHEA-treated groups received powdered chow containing 0.6% DHEA ad lib for 16 weeks. Another group of obese rats was pair fed to match the intake of the obese DHEA-treated rats. At the end of this period, trunk blood was collected from fasted rats for assay of E-like immunoreactivity (E-LI) by ELISA. DHEA treatment caused a significant diminution in circulating E-LI in both lean (control: 2030 +/- 226; treated: 752 +/- 145 ng/mL; n = 10, p < 0.0001) and obese (control: 2489 +/- 391, n = 6; treated: 1123 +/- 185 ng/mL, n = 7; p = 0.0003) rats. Because DHEA treatment decreases caloric intake and body weight, we examined the effect of caloric intake and body weight on E-LI levels. Serum ELI levels were lower in the obese DHEA-treated group compared to that of obese pair fed (pair fed: 1589 +/- 313, n = 6; DHEA: 1123 +/- 185 ng/mL, n = 7), but the differences were statistically insignificant (p = 0.185). Also, both weight-matched lean and obese control rats had significantly (p < 0.008) higher E-LI than their DHEA-treated counterparts. To examine whether the decrease in serum E-LI following DHEA treatment could be due to increased peptide metabolism, the rate of disappearance of endogenous E-LI from serum (obese control and DHEA-treated) at 37 degrees C was evaluated. The results show an attenuation of peptide metabolism in serum from DHEA-treated rats, a finding contrary to our expectations. In summary, DHEA treatment lowers serum E-LI levels both in lean and obese Zucker rats. This decrement in peptide level is not secondary to changes in body weight or caloric intake due to DHEA, or due to altered serum peptide metabolism. Although DHEA appears to be a potent modulator of E-LI levels, the relationship between DHEA and E-LI in relation to appetitive behavior remains to be clarified.

Animals↗
PubMedDate not supplied

Appetitive responses to computer-generated visual stimuli by the praying mantis Sphodromantis lineola (Burr.).

Tethered adult female praying mantises, Sphodromantis lineola (Burr.), were presented with various computer-generated visual stimuli that moved against patterned or homogeneous white backgrounds in predetermined patterns and at predetermined speeds. The degrees to which the stimulus configurations elicited appetitive behaviors (attempting to approach and/or striking) indicated the relative degrees to which the stimuli were classified as prey. Mantises readily struck at cartoon "crickets" that subtended visual angles as great as 24.5 deg x 62.5 deg, but response rate was suppressed if the stimuli were superimposed on horizontally moving patterned backgrounds. Mantises also displayed appetitive behaviors to moving black squares (edge lengths = 10-47 deg) that moved in predetermined "erratic" paths; however, their response rates were affected by several factors: (1) response rate declined as edge length increased over 10 deg; (2) striking was emitted to stimuli viewed from 23 mm (but not farther) away; and (3) both stimulus displacement rate (distance moved between video frames) and apparent speed (video frame rate) dramatically affected the releasing strength of the stimuli. Finally, mantises responded appetitively to random dot patterns moving synchronously against identically patterned backgrounds and to pairs of black squares moving synchronously against a white background. However, in the latter case, response rate declined as the squares were moved farther apart horizontally or vertically. These and previous results from our laboratory on mantises are congruent with behavioral results obtained from other insects such as flies (Diptera) and dragon flies (Odonata) and suggest that there are neuroanatomical similarities between these groups.

Animals↗
PubMed2004

Dopamine in the orbitofrontal cortex regulates operant responding under a progressive ratio of reinforcement in rats.

Prefrontocortical dopamine (DA) plays an essential role in the regulation of cognitive functions and behavior. The orbitofrontal cortex (OFC) receives a dopaminergic projection from the ventral tegmental area and is particularly important for goal-directed appetitive behaviors and for the neural representation of reward value. We here examined the effects of DA receptor blockers locally infused into the OFC, on instrumental behavior under a progressive schedule of reinforcement. After continuous reinforcement training (lever pressing for casein pellets) rats received bilateral intra-OFC-infusions of the DA D1-receptor antagonist SCH23390 (3 microg/0.5 microl), the DA D2-receptor antagonist sulpiride (3 microg/0.5 microl), or phosphate buffered saline through chronically indwelling cannulae. Immediately after infusion they were tested under a time-constrained progressive ratio schedule of reinforcement (3, 6, 9, 12, ... lever presses for 1 casein pellet within 180 s). Both SCH23390 and sulpiride led to a significant reduction of the break point (cessation to respond to the increasing criterion of instrumental effort) compared to vehicle infusions. A food preference test revealed no drug effects on the amount of consumed pellets and on the preference of casein pellets over laboratory chow. Leftward shifts of the break point in progressive ratio tasks indicate a disturbance of the mechanisms that translate motivation into appetitive behavior under conditions of increasing instrumental effort. Therefore, our data indicate that orbitofrontal dopamine is necessary for reward-related instrumental behavior.

Analysis of Variance↗
PubMed2005

The hypothalamic neuropeptide melanin-concentrating hormone acts in the nucleus accumbens to modulate feeding behavior and forced-swim performance.

Melanin-concentrating hormone (MCH) is a hypothalamic neuropeptide with a prominent role in feeding and energy homeostasis. The rodent MCH receptor (MCH1R) is highly expressed in the nucleus accumbens shell (AcSh), a region that is important in the regulation of appetitive behavior. Here we establish a role for MCH and MCH1R in mediating a hypothalamic-limbic circuit that regulates feeding and related behaviors. Direct delivery of an MCH1R receptor antagonist to the AcSh blocked feeding and produced an antidepressant-like effect in the forced swim test, whereas intra-AcSh injection of MCH had the opposite effect. Expression studies demonstrated that MCH1R is present in both the enkephalin- and dynorphin-positive medium spiny neurons of the AcSh. Biochemical analysis in AcSh explants showed that MCH signaling blocks dopamine-induced phosphorylation of the AMPA glutamate receptor subunit GluR1 at Ser845. Finally, food deprivation, but not other stressors, stimulated cAMP response element-binding protein-dependent pathways selectively in MCH neurons of the hypothalamus, suggesting that these neurons are responsive to a specific set of physiologically relevant conditions. This work identifies a novel hypothalamic-AcSh circuit that influences appetitive behavior and mediates the antidepressant activity of MCH1R antagonists.

Analysis of Variance↗
PubMed2000

Intrinsic and extrinsic modulation of a single central pattern generating circuit.

Intrinsic and extrinsic neuromodulation are both thought to be responsible for the flexibility of the neural circuits (central pattern generators) that control rhythmic behaviors. Because the two forms of modulation have been studied in different circuits, it has been difficult to compare them directly. We find that the central pattern generator for biting in Aplysia is modulated both extrinsically and intrinsically. Both forms of modulation increase the frequency of motor programs and shorten the duration of the protraction phase. Extrinsic modulation is mediated by the serotonergic metacerebral cell (MCC) neurons and is mimicked by application of serotonin. Intrinsic modulation is mediated by the cerebral peptide-2 (CP-2) containing CBI-2 interneurons and is mimicked by application of CP-2. Since the effects of CBI-2 and CP-2 occlude each other, the modulatory actions of CBI-2 may be mediated by CP-2 release. Although the effects of intrinsic and extrinsic modulation are similar, the neurons that mediate them are active predominantly at different times, suggesting a specialized role for each system. Metacerebral cell (MCC) activity predominates in the preparatory (appetitive) phase and thus precedes the activation of CBI-2 and biting motor programs. Once the CBI-2s are activated and the biting motor program is initiated, MCC activity declines precipitously. Hence extrinsic modulation prefacilitates biting, whereas intrinsic modulation occurs during biting. Since biting inhibits appetitive behavior, intrinsic modulation cannot be used to prefacilitate biting in the appetitive phase. Thus the sequential use of extrinsic and intrinsic modulation may provide a means for premodulation of biting without the concomitant disruption of appetitive behaviors.

Action Potentials↗
PubMed2001

A study of the antidepressant activity of Hypericum perforatum on animal models.

The treatment of non-selected depressed patients with a hydro-alcoholic extract of Hypericum perforatum has been reported to have an efficacy similar to that of classical antidepressants. The effects of H. perforatum on three animal depression models have been studied: (a) an acute form of escape deficit (ED) induced by unavoidable stress; (b) a chronic model of ED, which can be maintained by the administration of mild stressors on alternate days; (c) a model of anhedonia based on the finding that repeated stressors prevent the development of appetitive behavior induced by vanilla sugar in satiated rats fed ad libitum. H. perforatum: (i) acutely protects animals from the sequelae of unavoidable stress; (ii) reverts the chronic escape deficit state maintained by repeated stressors and (iii) preserves the animal's capacity to acquire motivated appetitive behavior. Exposure to chronic stress not only induces escape deficit, but also decreases extraneuronal levels of dopamine in the nucleus accumbens shell; both behavioral and neurochemical effects are reverted by long-term treatment with antidepressants. Three-week treatment with H. perforatum reverted the chronic stress effect on extraneuronal dopamine in the nucleus accumbens. A consistent body of data in the literature suggests that, among the components of H. perforatum extract, hyperforin is the compound (or one of the compounds) responsible for the antidepressant activity. We compared the efficacy of the total extract with the efficacy of hyperforin after p.o. administration. In the acute-escape deficit model, hyperforin showed a potency of about ten times that of the total extract in protecting rats from the sequelae of unavoidable stress. Thus, hyperforin appears to be the most likely active component responsible for the antidepressant activity of H. perforatum.

Animals↗
PubMed1999

Contingent negative variation in children with anorexia nervosa.

BACKGROUND: Central catecholamines, particularly dopaminergic and noradrenergic systems, have affected the appetitive behavior in patients with anorexia nervosa (AN). The purpose of this study is to distinguish the characteristics of contingent negative variation (CNV) and postimperative negative variation (PINV), which may reflect the level of catecholamine in children with AN. METHODS: Eight children with AN aged 10 to 15 years and 23 age-matched healthy children were recruited. Contingent negative variation was recorded from the frontal midline (Fz), central midline (Cz) and parietal midline (Pz) referenced to linked earlobes during 30 trials consisting of a warning stimulus and an imperative stimulus with an interstimulus interval of 2 s and an intertrial interval of 10 s. The imperative stimulus of each trial required a button press. RESULTS: Children with AN had a diminished amplitude of the CNV. They had a significantly more attenuated early CNV and late CNV amplitude at Cz than normal children. No significant differences were observed between AN children and normal children in the amplitude of PINV at all three electrode sites. No difference could be found between the two groups in the frequencies of normal and abnormal duration of PINV. CONCLUSION: These findings suggest that early CNV may be diminished by norepinephrine deficiency and late CNV may be attenuated by dopaminergic deficiency in children with AN. Reduced CNV may represent impaired cognitive processes which reflect impaired appetitive behavior in AN children.

Adolescent↗