Behavioral biology最新文献

Male rats were reared under one of the following conditions from 14 days of age: (1) Isolation (raised in individual cages); (2) Contact isolation (isolation except for Days 40–60 when two females lived close to the male, separated only by a screen); (3) Cohabition with males prepuberally (males together between Days 14 and 40); (4) Cohabition with males postpuberally (males together between Days 40 and 60); or (5) Cohabition with females (male together with females between Days 40 and 60). When 75 days old, the rats were subjected to penile deafferentation by pudendal nerve transection and tested for masculine sexual behavior. The Group 5 males showed more intromission patterns than those of Groups 1, 2, and 3 and more ejaculation patterns than those of Groups 1, 2, 3, and 4. It was concluded that postpuberal heterosexual experience controls the expression of sexual behavior in two ways: (a) by increasing the readiness to initiate mounting behavior and (b) by facilitating the display of a complete mating pattern.

The initiation of suckling (nipple approach and attachment) was not affected by gastric preloads in 10- and 20-day-old rat pups tested with their anesthetized mother. However, food intake was affected. In 10-day-old pups nutritive and nonnutritive loads depressed diet intake during suckling by the same amount and apparently as a result of severe gastric distension. In contrast, the diet intake of 20-day-old pups was differentially depressed by nutrivive preloads, suggesting an emerging postgastric or postabsorptive control of ingestive behavior.

Preferences for eight concentrations of sodium chloride were measured in 10 control rats, 10 rats fed a diet supplemented with 2.5% methionine, and 10 rats fed a diet supplemented with 2.5% methionine and 2% zinc sulfate. All rats received the applicable diet for 21 days before testing was initiated with a 48-hr, two-bottle preference paradigm. Results of the study indicated that rats supplemented with methionine alone had significantly greater preferences for the salt solutions than rats from either of the remaining groups. Dietary treatment did not affect total volume intake (milliliters per gram body weight). Further analysis of the separate water and sodium chloride solution volume intakes demonstrated that while all groups consumed essentially equivalent amounts of water, the rats supplemented with methionine alone consumed significantly increased amounts of the salt solutions, thus manifesting an increased percentage preference. The results indicate that methionine, a thiol-containing amino acid, can alter preferences for sodium chloride solutions and that this effect can be reversed by zinc supplementation. The etiology of this change in preference behavior may be related to either decreased gustatory sensitivity (mediated by zinc depletion and/or thiol supplementation) or to salt craving (mediated by kidney and/or adrenal dysfunction).

A new cognitive learning task has been devised in the rat. The subjects, presented with a specific stimulus (stimulus session), must afterward (testing session) recognize this stimulus among the three presented in order to obtain their reinforcement (water). The stimulus changes randomly for each trial. Once the rule has been learned, performance remains stable and a delay of up to 30 min can be placed between stimulus session and testing session without significantly affecting performance. The length of the maximum delay is a function of the duration of the stimulus session. Such long delays allow experimental manipulation of this specific memory trace.

In these experiments we tested the hypothesis that the same afferent systems which mediate vomiting reflexes also participate in conditioned taste aversions which are formed when ingestion of a taste cue is paired with subsequent internal malaise. Borison and Wang have shown that emetic reflexes in dogs and cats are integrated in a brainstem center which responds to local gastric irritation mediated by the vagus or to bloodborne toxins monitored by brain stem chemoreceptors. This same afferent system may mediate taste-illness conditioning since the emetic center is anatomically associated with the relay nucleus for primary taste afferents. We have shown that subdiaphragmatic vagotomy in rats disrupts the acquisition of a saccharin aversion induced by repeated conditioning trials with low doses of intragastric or intraperitoneal copper sulfate. In contrast, there is little effect on the aversion produced by a single, larger dose of copper sulfate injected directly into the blood via the tail vein, although vagotomized rats displayed an accelerated extinction pattern. These results parallel reports on the effect of vagotomy on vomiting reflexes in dogs and suggest a functional relationship between acute vomiting reflexes in dogs and suggest a functional relationship between acute vomiting reflexes which eject poison and chronic conditioned taste aversions which inhibit subsequent ingestion of poison; further, they provide evidence that these responses are subserved, at least in part, by similar neural mechanisms.

The effect of lesions in the amygdala or dorsal hippocampus on the acquisition and generalization of a taste aversion was investigated. Rats were conditioned to avoid a 16% sucrose solution using a two-bottle technique. Once conditioning was established, a bottle containing the 16% solution was paired with either a 32, 24, 8, or 4% sucrose solution or water for 30 min/day for 5 days. No differences were observed in either the number of days to acquisition or in generalization gradients for any of the conditioned-aversion groups. In the generalization test, these subjects demonstrated a preference for sucrose concentrations below 16%. Control animals that received injections of saline rather than poison demonstrated a significantly lower preference relative to the poisoned animals for the lower sucrose concentrations.

The involvement of the adrenal glands in the induction of electroconvulsive-shock amnesia was examined. Sham-adrenalectomized rats given an electroconvulsive shock immediately following a single passive avoidance acquisition trial showed amnesia when tested 24 hr after training. Bilateral adrenalectomy 10 days before training protected rats against the disruptive effects of electroconvulsive shock on passive avoidance behavior.

Male Charles River rats were offered diazepam either orally or by counterinjection over a 6-day period, with drug concentrations increasing every other day. Although diazepam intoxication was observed at all drug concentrations and with increasing severity as the drug concentration was increased, no decrease in intake ensued. This apparent lack of conditioned aversion formation was not due to diazepam-induced amnesia, since rats poisoned with lithium chloride after diazepam consumption showed no attenuation of conditioned aversion when compared to rats poisoned after drinking flavored water.