Behavioral and neural biology最新文献

Post-training administration of morphine (0.25, 0.5, or 1 mg/kg) dose-dependently impairs retention of an inhibitory avoidance response in mice. The effects on retention performance induced by the drug appear to be due to an effect on memory consolidation. In fact, they were observed when drugs were given at short, but not long, periods of time after training, i.e., when the memory trace was susceptible to modulation. Moreover, these effects are not to be ascribed to an aversive or a rewarding or nonspecific action of the drugs on retention performance, because the latencies during the retention test of those mice that had not received a footshock during the training were not affected by post-training drug administration. Pretreatment with either selective D1 or D2 dopamine (DA) receptor antagonists SCH 23390 and (-)-sulpiride administered at per se noneffective doses (0.025 and 6 mg/kg, respectively) potentiated the effects of morphine, while either selective D1 or D2 receptor agonists SKF 38393 and LY 171555 at per se noneffective doses (5 and 0.25 mg/kg, respectively) antagonized the effects of the opiate on memory consolidation. No significant differences were evident between the effects of D1 and D2 receptor active compounds, thus suggesting that D1 and D2 receptor types are similarly involved in the effects of morphine on memory consolidation, in agreement with previously reported results. These results are discussed in terms of a possible inverse relationship of endogenous opioid and DA systems in the brain that are involved in memory processes.

Four groups of male Wistar rats showing disrupted inhibitory avoidance conditioning due to striatal lesions were studied. Three groups received striatal, cortical, or ventral mesencephalic brain grafts and the fourth group remained as a lesioned control. Sixty days postgraft the animals were retrained in an inhibitory avoidance task. The striatal-grafted animals were the only group that significantly improved in the ability to acquire the inhibitory avoidance task. Acetylcholinesterase histochemistry revealed positive patches of cells in the striatal grafts. Cortical grafts showed less reactivity, without patches. Immunocytochemical analyses for tyrosine hydroxylase revealed positive cell reactivity in the mesencephalic grafts and few positive fibers were detected in the border between the striatal grafts and the host tissue. These results demonstrate that striatal but not cortical or mesencephalic brain grafts can promote the restoration of the ability to acquire an inhibitory avoidance task and suggest that the acetylcholine tissue content is involved in the behavioral recovery.

Ten different behavioral tests were performed on a population of young (n=20) and aged (n=20) Fischer 344 rats. The relationship structure among these tests was studied by principal component analysis applied both to the entire data set and separately to the two age groups. This analysis proved very useful in highlighting a global index of the rat “behavioral” age based on the entire test set. The analysis effected separately on the two age groups evidenced qualitative differences between them that were linked to the different meaning the same test would assume in rats of different ages. From an overall methodological viewpoint, this work indicates that the correlations among behavioral parameters appear to depend on the observational scale and that the spin-glass model represents an appropriate metaphor to approach the study of the correlations in biological systems.

In the present experiment the effect of a conditioned inhibitory stimulus on tolerance to scopolamine-induced adipsia was evaluated. Long-Evans rats were injected with 0.6 mg/kg scopolamine bromidrate in the presence of a tone or a noise, and physiological saline with a compound tone-oder. A summation test with the compound stimulus noise-odor showed a tolerance reversal effect to scopolamine adipsic effects in tolerant subjects. This reduction of tolerance was similar to adipsia produced by the first scopolamine administration, only when the odor stimulus was present. However, the inhibitory stimulus alone has no effect upon water intake. Results confirmed that a Pavlovian conditioned inhibition procedure can reduce conditioned tolerance to a drug.

Two experiments studied the adjustment of toads (Bufo arenarum) to partial reinforcement in a runway. In Experiment 1, two groups received 24 daily trials of either continuous reinforcement (CR) or 50% partial reinforcement (PR). Training parameters that facilitate the PR extinction effect (greater resistance to extinction after PR than CR training) in rats were selected. PR impaired performance during acquisition but had no effect on performance during extinction relative to CR. In Experiment 2, four groups were trained in a factorial design involving CR and PR, and a lesion of the medial pallium and a sham operation. Performance during acquisition was again impaired by PR, but the medial pallium lesions had no effect. The lesion, however, increased resistance to extinction after both CR and PR training. The results are discussed in relation to comparative research on learning and to the hypothesized homology of the amphibian medial pallium and the mammalian hippocampal formation.

Respiratory pumping in Aplysia is a spontaneously occurring behavior whose neural circuitry has been explored, but whose natural functions are incompletely understood. Respiratory pump rate was examined in freely behaving pairs of Aplysia fasciata, to determine whether it is modified by the occurrence of mating and other behaviors. The background rate of respiratory pumping was ∼2/hour. This rate was maintained while animals were immobile, moving in place, crawling, or feeding. The rate was inceased to over 8/hour during courtship and to ∼4/hour during female mating and was reduced to ∼1/hour during male-mating. These data suggest that respiratory pumping has a reproductive function, perhaps in dispersal of pheromones that are released during female-mating and courtship. Respiratory pumping never occurred while animals were swimming, suggesting that respiratory pumping and swimming may be mutually incompatible behaviors. Respiratory pumping was less common by night than by day.

The effect of reserpine on the serotonin content of the central nervous system and the feeding behavior of the carnivorous leech Haemopis marmorata was investigated. Leeches were hand-fed to satiation by presentation of pieces of chicken liver held in forceps for three meals at 4-day intervals prior to and 1 week following three consecutive injections of 100 μg reserpine in the crop. A group matched by weight and preinjection food intake was injected with the vehicle in a blind experimental design. Histochemical and chemical determinations showed that reserpine effectively depleted the serotonin content of the animal's central nervous system. Furthermore, the food intake of reserpine-treated animals was significantly less than that of the sham-injected group. However, the depleted animals continued to ingest approximately 40% of the amount consumed during the preinjection period. These results show that reserpine successfully depleted the serotonin in the carnivorous leech H. marmorata and decreased the food intake of this leech species. They suggest that feeding behavior in Haemopis is partially but not exclusively dependent on serotonin and that, in contrast to the sanguivorous leeches, additional factors may be necessary for its regulation.

Three experiments were conducted to examine the effectiveness of different forms of tactile stimulation, probe and stream, and interstimulus intervals (ISI) in producing habituation in the polypoid sessile stage of the jellyfish Aurelia aurita. Results from Experiment 1 showed that polyps significantly decreased their responsiveness to both forms of tactile stimulation with 30-s ISI across 60 trials. Response to a novel stimulus indicated that the response decrement had not been due to fatigue. When the ISI was lengthened to 6 min in Experiment 2, response to the probe form of tactile stimulation did not significantly decrease across 20 trials. Using an ISI of 1 min in Experiment 3, response to the probe form of tactile stimulation decreased significantly across 40 trials. A significant increase in response to the original stimulus (dishabituation) following presentation of a novel stimulus indicated that response decrement was due to habituation or a habituation-like process rather than simple effector fatigue or sensory adaptation.

The development of brain stem auditory-evoked potentials (BAEP) was studied in devocalized ducklings reared in auditory isolation and in vocal ducklings exposed to enhanced species-specific auditory stimulation with embryonic contact-contentment calls (CTs). Thresholds and latency of BAEP wave P₁ in the mute ducklings indicated that even short-term auditory deprivation affected the development of auditory sensitivity, substantially reducting the rate of decline in BAEP thresholds and latencies of P₁, especially in the low-frequency (500 and 750 Hz) and high-frequency (above 2.0 kHz) ranges. The ducklings exposed to enhanced stimulation, on the other hand, showed an accelerated decline in BAEP thresholds and latencies of P₁ across all test frequencies, with the most marked influence on low (below 1.5 kHz) and high (above 2.5 kHz) frequencies. The influence of species-specific auditory experience had its most potent effect during the embryonic critical period for postnatal auditory perceptual (behavioral) development, at which time the embryo produces and hears a special low-frequency (1.5–2.5 kHz) version of its own contact-contentment vocalization.

A role for the 5-HT_1A receptor in learning and memory has been suggested by diverse evidence. The present paper deals with the acute effect of 8-OH-DPAT (a 5-HT_1A agonist) administered to rats before or after training in an autoshaped lever-press response (a model of associative learning). The results show that 8-OH-DPAT improved consolidation of the conditioned response (CR) when injected post-training, but impaired it with pretraining administration. Both effects were time-dependent. When the compound was administered pre- or post-training to free-feeding or prefeeding animals, they did not learn the CR. When it was administered to retrained food-deprived animals, the compound was also inactive. However, with retrained animals on a free-feeding schedule, pre- or post-training administration of 8-OH-DPAT enhanced retrieval in a dose-dependent fashion. Pretraining administration of 8-OH-DPAT impaired food intake and exploration, and therefore learning. The present results strongly suggest a role of 5-HT_1A receptors in the consolidation and retrieval of learning. Such improvement is independent of food intake.