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Results for “Appetitive Behavior”

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PubMedDate not supplied

Increased acquisition of a complex appetitive task after MSH and MIF.

After daily injections of melanocyte stimulating hormone (MSH), MSH-release inhibiting factor (MIF), or diluent albino rats ran a 12 choice Warden maze for a palatable food reward. Rats receiving the hormones had shorter latencies and made fewer errors than controls during learning but, unlike results with simple tasks, there were no differences during extinction. The results demonstrated that both MSH and MIF-I could facilitate the acquisition of an appetitive task which seemed of sufficient complexity to emphasize differences in performance.

Animals↗
PubMed1985

The role of central noradrenergic neurons in electroconvulsive shock-induced muricide inhibition in olfactory bulbectomized rats.

In order to elucidate the role of central monoaminergic neurons in electroconvulsive shock (ECS)-induced muricide inhibition in the olfactory bulbectomized rat (OB rat), we examined the effect of chemical or electrical lesions of each monoamine-containing neuron on ECS-induced muricide inhibition. ECS-induced muricide inhibition was antagonized by 6-hydroxydopamine (6-OHDA) treatment and locus coeruleus lesions, while it was unaffected by desipramine + 6-OHDA, substantia nigra lesion, and desipramine + 5,7-dihydroxytryptamine. The present results strongly suggest that ECS-induced muricide inhibition of the OB rat is due to increased activity of the noradrenaline but not of dopamine and serotonin neurons.

Adrenergic Fibers↗
PubMed1986

Synthesis of rat brain DNA during acquisition of an appetitive task.

We have examined the incorporation of [3H-methyl]thymidine into DNA extracted from several brain regions of rats learning a reverse handedness task, of control rats allowed to use their preferred paw, and of control rats left in their home cages. In learning animals, decrements in percent incorporation were observed in the visual cortex, remaining brain, hippocampus and entorhinal cortex. In the latter two regions less marked decreases were present in the active control group. No variation occurred in the sensory-motor cortex. In learning rats the specific radioactivity of neuronal DNA was markedly decreased in the hippocampus and remaining brain. In the former region, a less marked decrease was present in active control rats. In subcellular fractionation studies it was observed that decreases in DNA specific radioactivity prevailed in the mitochondrial fraction isolated from the hippocampus and visual cortex of learning rats. Brain radioactive DNA was widely distributed among fractions differing in their degree of repetitiveness. Its pattern of distribution did not coincide with that of bulk DNA and differed significantly among behavioural groups. The results suggest a non random origin of newly-synthesized brain DNA and its involvement in learning.

Animals↗
PubMed1991

Effect of the 5-HT2 antagonist ketanserin on salt appetite in the rat.

The 5-HT2 antagonist ketanserin inhibited salt appetite induced by subchronic deoxycorticosterone acetate (DOCA) treatment, as well as salt appetite induced by sodium depletion (which is governed by the synergy of aldosterone and angiotensin in the brain). The effect of ketanserin was more evident following intraperitoneal than intracerebroventricular injection. On the other hand, ketanserin did not inhibit either salt intake induced by intracranial renin injection, or the need-free salt intake of the multidepleted female rat, which is not dependent on the renin-angiotensin-aldosterone system. These findings suggest that the antinatriorexic action of ketanserin is selective for the mineralcorticoid mechanisms controlling salt appetite. Ritanserin, too, a potent 5-HT2 antagonist showing a different receptor selectivity profile from that of ketanserin, suppressed DOCA-induced salt appetite, thus supporting the involvement of 5-HT receptors in the antinatriorexic action. DOCA treatment alters serotonin metabolism in the central nervous system and it has been proposed that changes in 5-HT metabolism may be important in the genesis of DOCA-induced hypertension. The present results indicate that ketanserin inhibits DOCA-induced salt appetite and suggest that serotoninergic mechanisms might be involved in the elicitation of mineralocorticoid-induced salt appetite.

Animals↗
PubMed1992

Effect of administration of an analog of LHRH on appetitive learning in young and middle-aged female rats.

Hypothalamic luteinizing hormone-releasing hormone (LH-RH) had been reported to induce changes in defensive learning. In middle age, females exhibit a decline in their reproductive axis. Several studies in rodents suggested that hypothalamic LHRH function deteriorated in middle-aged females. Our experiments compare T-maze learning in young and middle-aged female rats and study the effect of administration of an analog of LHRH, D-Trp6-LHRH. The ovarian action of the analog was studied and a gonadectomized control group was added. No differences were observed between young and middle-aged females in acquisition, retention, and reversal of a simple discrimination in the T-maze. However, after removal of motor and spatial cues acquisition of the discrimination on visual cues was impaired in middle-aged females compared to young mature ones. Administration of D-Trp6-LHRH enhanced performance during the visual discrimination in younger females and had no action in middle-aged ones, whereas it inhibited ovary function in both groups. Ovariectomy had no effect. These results suggest a direct effect of the analog of LHRH on the CNS and show that this peptide fails to counteract the deleterious effect of age on performance.

Aging↗
PubMed1994

Phenytoin and phenobarbital: a comparison of their state-dependent effects.

Two commonly used antiepileptic drugs, phenytoin sodium and phenobarbital sodium, were investigated for state-dependency effects at different doses. Male Wistar strain rats trained to a criterion in an inhibitory avoidance task and a food-motivated T-maze task under varying drug and nondrug states were subjected to retention tests 24 and 48 h, respectively, following acquisition. The treatment instituted at the time of retrieval was either the same as, or different from, that used during training. The results indicated that phenytoin produced state-dependency effects at test doses of 20, 40, and 60 mg/kg in the avoidance task and at test dose of 20 mg/kg in the T-maze task experiments. These state-specific effects were comparable to those of phenobarbital sodium (5 and 10 mg/kg). The reinstitution of the drug state in an additional test session produced approximately equal and significant recovery of conditioned responses in the T-maze paradigm both in phenytoin and phenobarbital groups. These results demonstrate, for the first time, the ability of phenytoin to produce state-dependency effects in a pattern similar to that observed with a widely studied compound such as phenobarbital. Overall, the data provide no support for the view that the degree of discriminability of a drug is an indicator of potential state-dependency effects and is restricted only to the dosage high enough to produce noticeable intoxication.

Animals↗
PubMed1990

The effects of aging in rats on working and reference memory performance in a spatial holeboard discrimination task.

The effects of aging on spatial memory performance of rats was studied in a holeboard task in which 4 of 16 holes were baited with food. Brown-Norway rats of five ages (4, 13, 19, 25, and 30 months) received a total of 80 acquisition trials. A clear age-related decline of spatial working and reference memory performance was found. The decline was most profound between 19 and 25 months of age. The speed of visiting holes and the development of a preferred pattern of hole-visits did not influence spatial discrimination performance. Correlational analysis supported the view that the working and reference memory measures represent distinct aspects of spatial memory.

Aging↗
PubMed1990

Diazepam-induced impairment of a go-no go successive discrimination.

Diazepam (2.0 and 4.0 mg/kg, but not 1.0 mg/kg) administered in eight acquisition sessions significantly impaired the light-cued successive discrimination of male Sprague-Dawley rats. In two postdrug (vehicle) sessions, groups previously treated with the drug demonstrated good recovery in discrimination. An analysis of response components indicated that the impairment was due to the failure of drugged subjects to inhibit or withhold responses during the no go periods of the task. These findings are consistent with a "disinhibitory hypothesis" of drug impairment. The similarity of the present findings to those previously reported with chlordiazepoxide suggests that such effects are a generalized characteristic of the benzodiazepine class of drugs.

Animals↗
PubMed1990

Delayed response, preoperative overtraining, and prefrontal lesions in the rat.

An earlier study in this laboratory found that preoperative overtraining improved retention of a delayed alternation task after prefrontal lesions in the rat. In this study, however, it was found that preoperative overtraining did not improve performance of the rat in a delayed response task following prefrontal lesions. These results support the hypothesis that preoperative overtraining can improve postoperative performance only when postoperative recovery is ordinarily present, as it is with delayed alternation. but not with delayed response, in the prefrontal rat. This suggests that effects of preoperative overtraining and postoperative recovery may be mediated by similar mechanisms. It further suggests that a shift of function, which seems to account for postoperative recovery, may occur in some parts of the normal adult brain as a result of overtraining.

Animals↗
PubMed1990

Nimodipine alters acquisition of a visual discrimination task in chicks.

Chicks 5 days old received intraperitoneal injections of nimodipine 30 min before training on either a visual discrimination task (0, 0.5, 1.0, or 5.0 mg/kg) or a test of separation-induced distress vocalizations (0, 0.5, or 2.5 mg/kg). Chicks receiving 1.0 mg/kg nimodipine made significantly fewer visual discrimination errors than vehicle controls by trials 41-60, but did not differ from controls 24 h later. Chicks in the 5 mg/kg group made significantly more errors when compared to controls both during acquisition of the task and during retention. Nimodipine did not alter separation-induced distress vocalizations at any of the doses tested, suggesting that nimodipine's effects on learning cannot be attributed to a reduction in separation distress. These data indicate that nimodipine's facilitation of learning in young subjects is dose dependent, but nimodipine failed to enhance retention.

Age Factors↗
PubMed1990

The effects of dorsal noradrenergic bundle lesions on spatial learning, locomotor activity, and reaction to novelty.

The dorsal noradrenergic bundle (DNB) of male Wistar rats was lesioned bilaterally using intracerebral injections of 6-hydroxydopamine neurotoxin. Some of the rats were trained in a water maze using an "alternation" strategy, where the two positions of the hidden platform in the pool were changed between successive trials in the daily tests, and other rats in a water maze, where the temperature of the water was lowered to about 11 degrees C. The rats trained in the cold-water maze were also tested in open-field and saccharin neophobia tests. No differences were found between the two groups in learning of water maze tasks or in locomotor activity in the open-field tests. However, the saccharin neophobia test revealed an increased neophobia in the DNB-lesioned rats.

Animals↗
PubMed1990

Lesions of the caudate nucleus selectively impair "reference memory" acquisition in the radial maze.

Groups of Long-Evans rats with bilateral lesions of the caudate nucleus, sham lesions, or no lesions were given one trial per day in an eight-arm radial maze. The same four maze arms were baited on each trial. The remaining four arms never contained food. Optimal performance required animals to enter each of the baited arms only once on each trial and to avoid entering the arms in the unbaited set. Rats with caudate lesions learned to enter each of the baited arms only once on each trial. However, these rats were severely impaired in learning to avoid entering the arms in the unbaited set. Implications for dual-memory theories are discussed.

Animals↗