Behavioral biology最新文献

Mrosovsky and Powley have recently argued that the term set point is a useful concept for describing the fact that body weight is maintained at a relatively constant value and is defended against challenges. This reply takes the position that the term set point, which refers to an input variable in a control system, should be used only as an input variable and then only when there is evidence that such a reference variable exists. Since stability of a controlled system can be maintained by a regulatory system which does not contain a set point the use of this term implies a particular type of control and should only be used when there is evidence for its existence.

Endogenous opiates (endorphins) mediate a variety of motivational and behavioral states. We examined the possible contributions of endorphins to the exploratory behavior of mice. Naloxone, a blocker of opiate receptors, depressed hole board exploratory activity and entry into a novel environment. It also reduced responding for sensory stimulation. Finally, a direct correlation was demonstrated between exploratory behavior on the one hand, and enkephalin-induced behavioral activation on the other.

Rats were implanted with a photocell on one side of the duodenum and a light emitting diode on the other. This permitted recordings of upper duodenal activity in the freely moving animal. Such recordings were made when rats were injected with the terminal octapeptide of cholecystokinin or saline as they fed to satiety. While cholecystokinin reduced intake by over 50%, the amplitude of duodenal activity after cholecystokinin injection was grossly attenuated as compared with activity after normal satiation. Food intake reduction after cholecystokinin injection may therefore be due to this abnormality rather than normal satiety.

Behavioral measures of freezing, open-field activity, wheel activity, and body weight fail to show that natural selection has significantly altered scores in wild Mus musculus over 10 generations of laboratory breeding.

Intraperitoneal injections of a wide range of doses of lithium chloride (LiCl) were given to two groups of Long—Evans rats. In the first group, the effect of the drug on the eating behavior of the animals was measured. In the second group, we tested whether the rats had learned a taste aversion to flavored fluids that had been paired with the LiCl injections. The administration of doses of LiCl that produced reductions in eating in the order of 50% (P < 0.05) did not produce learned taste aversion. These results indicate that a decrease in food intake is a more sensitive test of malaise than the learning of a taste aversion. Therefore, the taste aversion test to rule out malaise as a possible explanation of reductions in eating in satiation research should be used with reservations.

Circulating testosterone concentrations of adult male pigtail macaques (Macaca nemestrina) were assessed in three social conditions: (1) subjects housed in a stable heterosexual group (continuous contact with females); (2) subjects housed in an all-male group (no contact with females); and (3) subjects housed in a newly established heterosexual group (female presence as novel stimulus). Pigtail males living continuously with females throughout the year did not exhibit seasonal cyclicity in testosterone values and maintained mean levels equivalent to those observed in the rhesus monkey during the breeding season. Members of all-male groups had mean testosterone concentrations equivalent to males living with females, but these values rose significantly following the addition of females to the group.

Attenuation of conditioned taste aversion by prior exposure to the conditioned stimulus (CS) has been called “learned safety.” Injection of imipramine, chlordiazepoxide, pentobarbital, scopolamine, or penicillin after the first CS exposure interfered with learned safety. Further experiments showed that this drug effect was not due to aversiveness of the drugs, generalized neophobia, retroactive state dependence, gustatory interference, impaired memory, or overshadowing of the CS and that the drug effect could be abolished by familiarization. Conditioned suspicion due to alteration of the internal milieu was proposed as a possible mechanism of the drug effect. Such suspicion can facilitate subsequent taste aversion but is not aversive in itself. Time-course studies suggested that conditioned suspicion may be yet another form of long-delay learning.

Food deprived rats were required to locate four pellets of food located in 4 of 16 holes in an enclosed arena. Three groups of animals were studied in 11 testing sessions: rats with bilateral hippocampal damage; rats with bilateral neocortical damage; and an unoperated group. Half of each group received haloperidol and half received saline injection 20 min before Sessions 4 through 10. No injections were given on the first three sessions or on the final, 11th session. Animals with hippocampal lesions visited more nonfood holes than control animals and did not develop consistent sequences of food-hole visits. The administration of haloperidol reduced the number of consistent sequences of food seeking behaviors by intact animals without significantly affecting the efficiency of performance as measured by the number of nonfood holes visited. Haloperidol reduced the number of visits to nonfood holes of animals with hippocampal lesions.

A water-soluble fraction, devoid of alkaloids, was isolated from Datura stramonium (leaves and seeds). This fraction greatly impaired retention of (i) discriminated avoidance learning, (ii) two-way active avoidance learning, and (iii) a food-reinforced instrumental learning. The retention impairment induced by the Datura extract in these learning tasks was not due to an effect on spontaneous locomotor activity nor to changes in the emotional reactivity of the animals. Preliminary chemical analysis suggests that the active principle of the Datura extract may be a small peptide. It is suggested that this active principle affects some memory processes.

Changes in food intake and body weight of hamsters were traced over the estrous cycle, pregnancy, lactation, and the postsuckling period. Food intake varied with the estrous cycle but did not increase during pregnancy. During the postpartum period food intake increased in proportion to litter size and body weight decreased. The postsuckling period was accompanied by a decrease in food intake and an increase in body weight. Prolactin injections did not maintain the elevated food intake during the postsuckling period nor stimulate food intake when administered for a 7-day period to virgin animals. The mechanisms and functional implications of the contrasting patterns of energy regulation in hamsters and rats are discussed.