Journal of comparative and physiological psychology最新文献

Pinch-induced catalepsy was readily obtained in five strains of mice following repeated administration of strong pinches at the scruff of the neck. This catalepsy outlasted the pinch by minutes and was more easily induced on retests 48 hr after the initial acquisition tests. Repetitive tail pinches and/or exposure to the testing procedure without pinches also resulted in immobility; however, this was weak in magnitude and short in duration. Treatments designed to prevent immobility between trials (swimming in water or housing in the home cage with normally behaving littermates) failed to block or modify pinch-induced catalepsy. Spacing the trials up to one pinch per 10 min did not affect the emergence of pinch-induced catalepsy, but at one pinch per 30 min it was abolished. Pinch-induced catalepsy is strikingly similar to the behavior elicited in mice when attacked by a cat. In both cases, immobility is produced by pinches or bites at the scruff of the neck, and it outlasts the duration of the stimulus. These results support the notion of pinch-induced catalepsy as an adaptive coping strategy, increasing the chance of survival in predator/prey confrontations.

The ability of cholinergic agents to influence hormone-dependent sexual behavior in female rats was examined. In the first experiment, female sexual behavior, indicated by the incidence of lordosis, was significantly increased in estrogen-treated female rats following bilateral infusion of a cholinergic receptor agonist, carbachol (.5 microgram/cannula), into the medial preoptic area of the brain. Infusion of an artificial cerebrospinal fluid vehicle failed to facilitate lordosis. The incidence of lordosis was normally highest 15 min after carbachol infusion, began to wane by 45 min, and had returned to control levels by 90 min. Further, centrally administered carbachol activated lordosis at lower levels of estrogen priming than did systemically administered progesterone. In a second experiment, female rats, brought into sexual receptivity by administration of estrogen and progesterone, received preoptic infusions of an acetylcholine synthesis inhibitor, hemicholinium-3. Significant reductions in the incidence of lordosis were observed following bilateral infusion of hemicholinium-3 (1.25 microgram/cannula). This inhibition of lordosis was prevented when carbachol (.5 microgram/cannula) was infused along with hemicholinium-3. Results confirm the importance of cholinergic influences on sexual behavior in female rats.

In a number of successive tests, grooming, swimming, and eating behaviors of decorticate rats were reexamined by evoking the behaviors in various circumstances (stimulus conditions). The rats showed normal-length grooming sequences during spontaneous home cage grooming; when grooming was elicited by removing the rats from their home cage and soaking their fur by a brief swim, grooming-sequence length was abbreviated. In cold (18 degrees C) water, they swam well and with exaggerated vigor and frequently inhibited forelimb movements; in warm (37 degrees C) water, they swam poorly and paddled with all four limbs. To eat small pieces of food, they sat up and used their forepaws as do normal rats, but they frequently dropped the food; they did not use their forepaws to eat large pieces of food. When given powdered food, they first tried to grasp it in their mouth while they scratched at the floor surface with their front limbs; thereafter, they became increasingly proficient in licking it up. Thus, in a narrow range of stimulus conditions, decorticate rats can make movements resembling those of normal rats. They also improve with practice in some (eating powdered food) but not other (forepaw immobility, eating large food pellets) tasks. The study shows that in order to elucidate the role of the cortex in control of motor behavior, it is necessary to obtain "behavior profiles" of each behavior by testing the animals repeatedly and under widely varying test conditions.

A series of experiments on the role of Pavlovian processes in tolerance to amphetamine-induced anorexia in rats was conducted. In Experiment 1A, tolerance to the suppressant effect of d-amphetamine (4.0 mg/kg) on milk consumption was substantially diminished in an environment not previously associated with drug administration. Experiment 1B supported the interpretation that Pavlovian compensatory conditioning rather than a nonassociative mechanism mediated this phenomenon. Experiment 2 examined the hypothesis that "contingent tolerance" results from an inadvertent manipulation of Pavlovian cues. As in previous research, tolerance was contingent in that it did not develop if the rats were not exposed to food under the influence of the drug. Tolerance developed only if access to food occurred under the influence of amphetamine, but as in Experiment 1A, it was substantially diminished in an environment not previously associated with drug administration. Thus, tolerance to amphetamine-induced anorexia was shown to be both contingent on previous experience with food in the drugged state and subject to Pavlovian control. No current explanation for the occurrence of contingent tolerance or for the control of tolerance by Pavlovian processes can at once account for both of these findings. Experiment 3 confirmed the hypothesis that interaction with the food stimulus would be necessary to extinguish tolerance. This finding is also problematic for any current behavioral theory of tolerance. It is proposed that interaction with food is necessary for the homeostatic regulation of disturbances in eating caused by amphetamine. When activated, this regulatory process operates by means of Pavlovian conditional compensatory processes.

Adult female rats given bilateral parasagittal knife cuts in the medial hypothalamus (VMH group) were hyperphagic and became obese on a chow diet, compared with sham-operated controls. The VMH rats also overconsumed, relative to controls, sucrose and glucose solutions during 30 min/day tests. Pretreating the VMH and control rats with atropine methyl nitrate (1.0, 5.0, or 10.0 mg/kg) reduced their intake of the sugar solutions in three out of five experiments, and in all experiments it suppressed their 24-hr chow intake. However, the VMH rats continued to drink more of the sugar solutions than did the controls after all atropine treatments, and in three out of four experiments their hyperphagia on the chow diet was not blocked by the atropine. The results do not support the hypothesis that vagally stimulated insulin release or other cholinergically mediated cephalic responses of digestion are essential for the expression of hypothalamic hyperphagia and finickiness.

This study determined whether the visual characteristics of a familiar (imprinted) model or the auditory characteristics of the species maternal call are more important in determining the maternal preferences of visually imprinted ducklings. Domestic mallard (Peking) ducklings were visually imprinted to a stuffed model of a mallard duck during a 30-min following trial at 24 hr after hatching. Simultaneous choice tests between the familiar mallard model and an unfamiliar red-and-white striped box at 48 hr and 72 hr confirmed the efficacy of the imprinting procedure: When both models were silent, subjects preferred to follow the familiar mallard model. However, when a recording of the mallard maternal assembly call was played from a speaker mounted inside the red box, subjects imprinted to the mallard preferred to follow the unfamiliar box rather than the familiar mallard model (Experiment 1). That preference was not due merely to the audiovisual stimulation provided by athe box, since when a recording of intermittent tones was played from the mallard model, subjects imprinted to the mallard still preferred to follow the red box emitting the mallard call (Experiment 2). Playing only the tones from the red box disrupted the stability of the subjects' imprinted preferences between the first and second tests but did not produce a preference for the box (Experiment 3). These results show that the mallard maternal call is more important than visual experience with an inanimate model in determining the maternal preferences of visually imprinted Peking ducklings.

Adult female rats were given ventromedial hypothalamic parasagittal knife cuts (VMH treatment) or control surgery (Con treatment), followed 10 days later by subdiaphragmatic vagotomy (Vag treatment) or sham vagotomy (Sham treatment). The hyperphagia and obesity produced by the VMH cuts to rats on a chow diet was completely blocked by vagotomy (VMH-Vag group). Vagotomy also inhibited the VMH rats' overconsumption of a 20% sucrose solution during 1 hr/day and 24 hr/day tests, which contrasts with the effects of atropine treatment. However, when offered a selection of palatable foods (cookies, sweet milk, high-fat ration) in addition to chow, the VMH-Vag rats overate and gained considerably more weight than did the Con-Vag rats or the Con-Sham rats. The Con-Vag rats, on the other hand, gained less weight than did the Con-Sham rats on the palatable diet. The results indicate that intact subdiaphragmatic vagi are not essential for the expression of VMH hyperphagia and finickiness, and they therefore question the role of vagally mediated cephalic responses in the hypothalamic hyperphagia syndrome. On the other hand, the results indicate that in brain-intact animals vagotomy suppresses the development of diet-induced obesity.

Norway rat dams have a chronic elevation in core temperature throughout the first 2 wk postpartum, a situation that makes them vulnerable to a further, acute rise in body temperature during contact with their young. Prolactin appears to contribute to the chronic elevation of maternal temperature, probably by stimulating the secretion of progesterone, which then elevates the maternal thermal set point.

The rewarding effect of habenular stimulation was studied in 65 rats. The animals learned to bar press for electrical stimulation of the medial or lateral habenular nucleus or the fasciculus retroflexus, but not the surrounding thalamic nuclei. The response rates were moderate and steady and not influenced by food or water deprivation. Habenular self-stimulation was significantly facilitated by placing lesions in the ipsilateral anterior part of the medial forebrain bundle (MFB). Similarly, MFB self-stimulation was enhanced by ipsilateral habenular lesions. Lesions centered in the region of median raphe nucleus suppressed habenular self-stimulation for more than 4 wk. Self-stimulation of median raphe was not affected by habenular lesions. The results show that habenular stimulation can produce a rewarding effect by exciting neurons in the region of the raphe nuclei but apparently without requiring the participation of the well-known MFB reward system.