Maternal influences on body temperature in the infant primate.

The following study investigated the diurnal variation in body temperature of the young monkey infant and assessed the role that the mother plays in the development of the temperature rhythm. Using an implantable biotelemetry system, core body temperature and motoric activity were evaluated in maternally-reared and hand-reared rhesus monkey infants across the first several months of life. Our results indicated that the nocturnal temperatures of hand-reared infants are lower than those of mother-reared infants at one month of age, and that there are persistent differences in the orientation and shape of the diurnal temperature rhythm. The initial thermal challenge and the prolonged rhythm shift may have implications for the normal development of several physiological systems in the hand-reared infant monkey.

Diurnal rhythms of body temperature, drinking and activity over reproductive cycles.

These studies describe diurnal rhythm changes in female rats during gestation and lactation. In Experiment I, we measured the diurnal temperature rhythm (DTR) of 20 females through gestation, lactation and the post-lactational period and found that rhythm amplitude decreased during gestation and increased during lactation. Phase changes were also common features of the DTR during these states. In Experiment II, we measured drinking rhythms in 12 females during lactation and post-lactation and found phase and amplitude changes that were similar to the DTR changes seen in Experiment I. In Experiment III, we correlated the behavior of lactating females with their DTR and found that there was a consistent internal organization between behavior and Tb regardless of the degree of change in the DTR during the postpartum period. Females showing large phase changes in their DTR patterns were distinguishable from those showing smaller phase changes, however, on the basis of the absolute temporal organization of their behavior during lactation. All phase and amplitude changes disappeared immediately after pups were removed from the cage.

Body temperature and sleep architecture in response to a mild cold stress in women.

Six women participated in a seven consecutive night polygraphic sleep study during which both 24-hour rectal, body temperature and wrist activity were continuously sampled and stored at one-minute intervals. The study was designed to investigate the effects of a mild nocturnal cold stress on thermoregulation and sleep. On nights 4 and 5, subjects slept naked, without any bedcovers (mild cold stress) in a warm (26.7-28.3 degrees C) room. The daily mean rectal temperature and the daily nadir (low point) of the circadian temperature rhythm (CTR) showed a significant decrease between the baseline and cold stress conditions. The lowered nadir resulted in a significant amplitude increase in the daily CTR between the baseline and cold stress conditions. There were no significant changes in activity levels across experimental conditions. The ability to maintain a sleep state was significantly impaired during the cold stress. Stage 4 slow wave sleep increased, while Stage 3 decreased in response to the cold stress condition, and there was an associated lengthening of the first NREM period. These data suggest that challenges to the thermoregulatory system can be used as a vehicle to systematically alter sleep architecture in humans.

Diurnal changes in thermoregulatory behavior in rats with medial preoptic lesions.

Rats with medial preoptic area (MPOA) damage lack adequate autonomic thermoregulatory reflexes but can behaviorally regulate their body temperatures (Tb) in the cold and heat. We examined the performance of such rats on 90-min behavioral thermoregulatory tests. Tests were conducted during the day and night to determine the preferred Tb at different phases of the circadian Tb rhythm. The amplitude of this rhythm was exaggerated after electrolytic MPOA lesions; differences of 3-4 degrees C between daily peaks and troughs were seen (from 37 degrees C during day to 40-41 degrees C at night) compared with control variations of only 1.5-2.0 degrees C (from 36.0-36.5 degrees C during day to 38 degrees C at night). When escaping cold during the day or night or when escaping heat at night, both MPOA-damaged and control rats maintained Tb within +/- 0.5 degrees C of initial values. When escaping heat during the day, control and MPOA-damaged rats allowed their TbS at the end of the 90-min behavioral tests to rise to normal night levels (38 degrees C for controls and 40-41 degrees C for MPOA rats). These results demonstrate that rats with MPOA damage behaviorally defend the different phases of their exaggerated Tb rhythm in a manner similar to that of controls. Therefore the exaggerated swings in Tb seen in these preparations have an active regulated component and are not simply passive results of an excessive rhythm in heat production or heat conservation.

Brood patch function for the ventral scent gland of the female Mongolian gerbil, Meriones unguiculatus.

Infants of gerbil mothers whose ventral scent gland has been excised were compared on a number of developmental indices with pups of mothers who had had an equivalent section of lateral skin removed. The removal of the mother's ventral scent gland retarded the offsprings' pattern of ultrasounding during the 1st 21 days of development. In addition, infants from such mothers showed a retarded righting reflex. Inhibitions in the developmental behavior of gerbil pups might have resulted from less effective heat transfer during mother-pup contact. Indeed, excision of the gland resulted in lower ventral temperatures. The duality of function of the gland as an odor source for communication and as a heat source for offspring development suggests integrated communicative and thermoregulatory processes.

Ingestional aversion learning in preweanling rats.

Ingestional aversions were conditioned in 12- and 15-day-old rats by infusing a .5% solution of saccharin into the oral cavity and following this oral infusion by the injection of lithium chloride. At both ages, subjects for which the saccharin exposure was followed by lithium injection within 2-3 min drank less when the saccharin solution was again presented by oral infusion 12 hr later; such suppressions of intake were not observed in subjects that previously received the saccharin and lithium in an unpaired fashion (Experiments 1 and 3). Ingestional aversions were also learned by 12-day-olds when a 30-min interval was introduced between saccharin exposure and lithium toxicosis but not when toxicosis was delayed by 120 min (Experiment 2). In contrast, 15-day-olds learned aversions with both the 30- and 120-min-delay intervals (Experiment 3). Despite the absence of long-delay learning in 12 day olds, ingestional aversions conditioned at 12 days of age were retained for 2 wk (Experiment 4). These results provide further evidence of the associative abilities of neonatal rats and illustrate a developmental aspect of long-delay learning.