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At least 1,459 records · Page 81Linked to original sources
PubMed1993

Amygdaloid NMDA and muscarinic receptors involved in working memory performance of rats.

In a three-panel runway task, the competitive N-methyl-D-aspartate (NMDA) receptor antagonist, 3-[(+-)-2-carboxypiperazin-4-yl]propyl-1-phosphonic acid (CPP) (56 ng/side), injected bilaterally into the basolateral subdivision of the amygdala, significantly increased the number of errors (attempts to pass through two incorrect panels of the three panel gates at four choice points) in a test of working memory. Intra-amygdaloid injection of the muscarinic receptor antagonist scopolamine (5.6 micrograms/side) also significantly increased working memory errors. In a test of reference memory, neither CPP nor scopolamine affected the number of errors when injected into the basolateral amygdala at doses up to 56 ng/side or 5.6 micrograms/side, respectively. These results indicate that processes mediated by NMDA and muscarinic receptors in the basolateral amygdala are involved in the performance of working memory, but not in reference memory.

Amygdala↗
PubMed1993

Discrimination of insulin-produced hypoglycemia in rats.

Hypoglycemia is an abnormal state that can be induced by administering insulin to a fasting animal. Rats were trained to discriminate the normal state of euglycemia from the hypoglycemia produced by injection of 6 units/kg insulin. A drug discrimination procedure was used with a two-lever operant response. Insulin or water injected 25 min prior to the operant sessions determined whether left or right lever presses were reinforced. During 40 training sessions, reliable discrimination of the insulin-produced cue developed. After insulin injection, mean blood glucose levels dropped to about 75% of preinjection values. At 12 min postinsulin injection, prior to the development of hypoglycemia, noninsulin responses were made. Noninsulin responses were also made after injection with 800 mg/kg ethanol, indicating that a novel interoceptive state did not substitute for the insulin-produced cue. Insulin injections produced less severe hypoglycemia in less food-deprived rats, which again gave noninsulin responses. Animals can be trained to recognize the insulin-produced state, which presumably involves hypoglycemia, and/or counterregulatory process evoked in response to the drop in blood glucose.

Animals↗
PubMed1993

Age differences in the controls of ring doves' pecking.

Three experiments investigated the endogenous and exogenous controls of ring dove pecking. Experiment 1 confirmed that deprivation modulates adult pecking although nondeprived subjects peak at high levels. Experiment 2 determined that the level of pecking in nondeprived birds is modulated by exogenous cues such as the salience of the seed. Experiment 3 analyzed some of the controls of pecking in squabs. Both nondeprived and deprived squabs pecked little on days 12 and 16 of life, but by day 18, deprived squabs pecked significantly more than nondeprived squabs. Squabs inexperienced with deprivation peck less when hungry than squab that have had previous experience with deprivation. The controls of feeding change between day 24 of life and adulthood as exogenous cues did not stimulate nondeprived squab pecking until day 24 of life.

Aging↗
PubMed1993

Anticonflict action of chlordiazepoxide in rats with combined lesions.

Lesions of brain areas thought to promote anxiety do not diminish the anticonflict effects of benzodiazepines (BZDs). After initial training in the lick-suppression conflict test, eight rats received electrolytic lesions of the amygdala, dorsal raphe, locus coeruleus, and mammillary bodies. Ten others received sham lesions. Postoperative testing revealed a significant increase in punished licking at two stages after surgery in lesioned animals when compared with their own preoperative baseline levels and with the punished licking of control animals. Systemic administration of chlordiazepoxide (CDP, 2.5-10.0 mg/kg) resulted in a comparable dose-dependent increase in punished licking in both groups. These results suggest that the several structures lesioned need not be intact for CDP to have an antianxiety effect. It appears that sites of anxiolytic action are much more widely spread than currently believed and that other brain areas should be considered.

Amygdala↗
PubMed1993

Context conditioning: positive reinforcing effects of various food-related stimuli.

Rats were subjected to context preference tests to investigate the degree to which various manipulations involving food stimuli can be used to appetitively condition contextual cues. One manipulation consisted of placing hungry rats in a context that contained food that they could consume. A second one involved exposure to a context containing food that could only be seen and smelled, without consumption being possible. A third type of manipulation consisted of exposing animals to a context after the consumption of a small meal in the home cage. Finally, hungry, control subjects were merely exposed to a context containing an empty food tray. Preference for the context was only enhanced after the first type of manipulation, indicating that the actual consummatory act constitutes the major source of reinforcement in the present procedure. Olfactory and visual food cues, as well as postingestional aftereffects in isolation, did not function as reinforces.

Animals↗
PubMed1994

LTP of mossy fiber-stimulated potentials in CA3 during learning in rats.

The study was done to determine whether long-term potentiation (LTP) of the potentials occurs at mossy fiber (MF)-CA3 synapses with the advance of learning in unrestrained and unanesthetized rats. The rats were divided into two groups, the test and control groups. The test group was given daily learning tasks in the radial arm maze, whereas the control group was similarly handled without learning tasks. Complete acquisition of learning was observed in the test group on day 5, and the learning was maintained over 3 days. Under freely moving conditions, a significant increase in population spikes (PS) elicited by MF stimulation with the progress in learning was observed in the test group, and the PS potentiation remained stable after day 4. Furthermore, on day 7, when MF stimulation-induced PS in the test group were compared with that in the control group in pentobarbital-anesthetized rats, the responses were comparatively higher in the former. As the training-induced PS potentiation in CA3 occurred with the advance of learning, these findings suggest that LTP in CA3 induced by learning may be related to memory storage.

Animals↗
PubMed1994

Effects of intranasal ZnSO4 irrigation on olfactory and trigeminal cues.

Intranasal irrigation with ZnSO4 solutions is used for experimental induction of anosmia. It is, however, unknown whether the trigeminal nerve is affected by the treatment. One day after irrigation (concentrations investigated were between 0.05-1%) the ability of food finding, an olfactory cue, was decreased in a concentration-dependent manner. The trigeminal effect was investigated from a reflexively induced decrease in respiratory rate due to n-propanol exposure. No impairment occurred at 1% ZnSO4. Anosmia was also seen 2-3 h after an irrigation with solutions of 0.05-1% ZnSO4. At the same time, 0.2 and 1% solutions in themselves decreased the respiratory rate due to reflexes from the upper and lower respiratory tract. A conspicuous systemic effect can be ruled out as the Zn++ antidote, CaNa2EDTA, had no effect on the decrease. A direct activation of the trigeminal nerve due to a reaction with a thiol group may explain the effect from the upper airways.

1-Propanol↗
PubMed1994

Age-related impairment of food anticipatory locomotor activity in rats.

In rats of various ages (11 weeks to 24 months), restricted feeding was carried for 6 successive days and food was withheld completely on the 7th day to assess the effect of aging on food anticipatory activity. When feeding was restricted to a single meal at a fixed time of day (1330-1730), rats exhibited intense locomotor activity from 1-3 h before feeding time (prefeeding activity). This prefeeding activity was still detected on the fasting day. In addition, intense locomotor activity was observed for 1330-1730 even on the fasting day (mealtime-associated activity). Thus, mealtime-associated activity of the fasting day became an another good index for food anticipatory activity. These results indicate that the rats had come to anticipate the mealtime. Both prefeeding and mealtime-associated activities were similar at 11 weeks and 9 months of age, but they were impaired at 12 and 24 months of age. In 11-week-old rats, there was a negative correlation between the level of mealtime-associated activity and the daily duration of access to food, but this relationship was absent in 12-month-old rats. The present study suggests that aging strongly impairs the manifestation of food anticipatory activity in rats.

Aging↗
PubMed1994

Exogenous cholecystokinin octapeptide in broiler chickens: satiety, conditioned colour aversion, and vagal mediation.

Intraperitoneal injections of 3.5, 7.0, 14.0, and 28.0 micrograms/kg of CCK-8 into free-feeding broiler chickens significantly reduced food intake and delayed feeding (p < 0.05). To determine whether CCK can condition preference or aversion and to investigate the latency and the reversal of the effect, a low (2 micrograms/kg) and a high (14 micrograms/kg) dose of CCK-8 were administered using the coloured food paradigm. One colour, the conditioning stimulus (CS+), was paired with injections of CCK-8; the other colour was paired with injections of saline (CS-). The 2 micrograms/kg dose of CCK-8 neither reduced food intake nor conditioned a colour aversion. The 14 micrograms/kg dose significantly reduced food intake and conditioned a colour aversion (p < 0.05). When vagotomy was performed, the 14 micrograms/kg dose of CCK suppressed feeding in sham-operated birds (p < 0.05) but not in vagotomized birds (p > 0.05). A significant aversion for the food paired with CCK was obtained in sham-operated birds (p < 0.001) but not in vagotomized birds (p > 0.05). It was concluded that IP injections of CCK-8 reduce food intake in broiler chickens and that chicks can learn to associate the colour of the food with injections of CCK, developing an aversion. It was also shown that the vagus nerve mediates the CCK satiety effects and that aversion conditioning to CCK is dependent upon intact vagal innervation of the viscera.

Age Factors↗
PubMed1995

Blockade of the discriminative stimulus effects of gamma-hydroxybutyric acid (GHB) by the GHB receptor antagonist NCS-382.

The present study was designed to assess the ability of the newly synthetized, selective gamma-hydroxybutyric acid (GHB) receptor antagonist, NCS-382, in blocking the discriminative stimulus effects of GHB in a T-maze, food-reinforced drug discrimination procedure. Two groups of rats were trained to run the left arm of the maze 30 min after the i.g. administration of either 300 or 700 mg/kg GHB and the right arm after water. Once discrimination was acquired, combination of different doses of NCS-382 (0, 12.5, 25.0 and 50.0 mg/kg, IP) and GHB training doses were tested for blockade of GHB discrimination. NCS-382 dose-dependently blocked GHB-appropriate responding in both the 300 and 700 mg/kg GHB rat groups. The results of the present study indicate that the discriminative stimulus properties of GHB are mediated via stimulation of GHB receptors.

Animals↗
PubMed1995

Magnetic field effects on spatial discrimination and melatonin levels in mice.

Previous research has demonstrated a decrement in spatial discrimination learning following exposure to a .30 Tesla magnetic field. It had been suggested that those findings might be the result of an interaction between the magnetic field and physiological ferromagnetic material (magnetite). In the present study, mice were exposed for 100 min to a 2.0 Tesla field and both their left-right discrimination learning ability and serum melatonin levels were compared with a control group. Results indicated a significant interference with spatial discrimination learning following exposure, but no significant differences in serum melatonin levels. These findings appeared to rule out magnetically induced melatonin fatigue as an explanation of the decrement in spatial learning, as opposed to other possibilities such as magnetic effects on brain magnetite. However, additional controls are suggested for future research.

Animals↗
PubMed1995

Methotrexate does not interfere with an appetitive Pavlovian conditioning task in Sprague-Dawley rats.

There has been considerable interest in developing an animal model of the neuropsychological toxicity of chemotherapeutic agents used in the treatment of patients with cancer, especially children, since these agents often cause significant, long-term neuropsychological deficits. Yanovski, Packer, Levine, Davidson, Micalizzi, D'Angio (13) recently proposed such a model based on their finding that methotrexate retarded the formation of aversive Pavlovian excitatory associations. The present experiment examined the generality of methotrexate induced cognitive impairments by testing rats in Appetitive Pavlovian Conditioning tasks and a Conditioned Taste Aversion paradigm. The results of our study revealed no impairment following methotrexate exposure on the Appetitive Pavlovian tasks or on the Taste Aversion task, relative to two control conditions. While there were a number of methodological differences between the present experiment and those conducted by Yanovski et al. (13), the present results question the robustness and generality of Yanovski's et al. (13) animal model.

Animals↗
PubMed1996

Why do pouched mice (Saccostomus campestris) hoard food?

The function of food hoarding in Saccostomus campestris was investigated by examining the effect of photoperiod and temperature on the amount of two different types of food that were eaten and stored in artificial burrows by pouched mice from four different localities which experience contrasting climatic regimes. Food consumption was influenced by a variety of factors including the type of food, the sex of the individual, photoperiodic and temperature conditions, and the locality from which the animals originated. Females did not hoard significantly more food than males, which might have indicated that the solitary females hoard additional food specifically to provision their young. There was also no evidence that pouched mice hoard food to prepare for future periods of food scarcity, because there was no significant effect of photoperiod or temperature on hoarding activity, and the geographical variation in hoarding observed was not related to differences in climatic conditions at the different localities. However, geographical differences in food consumption and food hoarding were similar so that populations which ate the most food also hoarded the most food. Likewise, hoarding was selective and directed towards preferred food items. It therefore appears that food hoarding in this species may simply be a component of feeding behaviour and possibly serves to limit the amount of time spent processing food outside the burrow.

Animals↗
PubMed1996

Spatial and visual discrimination learning in CD1 mice: partial analogy between the effect of lesions to the hippocampus and the amygdala.

CD1 mice with dorsal hippocampal and central amygdaloid lesions were submitted to three radial eight-arm maze tasks requiring various degrees of spatial and nonspatial information processing. The results show that, on the standard version of the radial maze, only hippocampal lesions disrupted performance. In the spatial four-baited path task, both hippocampal and amygdaloid lesions increased the errors and modified the patterns of arm choice. Finally, on the visually cued four-baited path task, the two lesions did not affect any quantitative aspect of performance but a strong and unexpected effect of amygdaloid lesions on the patterns of arm choice was found. Taken together, the results indicate i) an effect of hippocampal lesions in all situations that require performing a spatial discrimination, and ii) an effect of amygdaloid lesions in all situations that require distinguishing between baited and unbaited arms, whatever the modality--spatial or visual--being relevant for discriminating the two sets of arms. The analogy between the effects of hippocampal and amygdaloid lesions specifically observed in the spatial four-baited path task suggests that these two limbic areas can exert a similar control on performance in tasks involving mapping operations based upon the discrimination of rewarded and nonrewarded reinforced locations.

Amygdala↗