Search PubMed⌕ Search

Biomedical subjects

M A Hofer

Publications and source records attributed to M A Hofer.

At least 91 records · Page 5Linked to original sources
PubMed1979

Sleep and temperature regulation during restraint stress in rats is affected by prior maternal separation.

During restraint stress, 30-day-old rats uniformly show an abrupt and persistent decrease in activity with a corresponding increase in quiet wakefulness. However, the effect of restraint on sleep and body temperature depends on whether maternal separation had previously occurred at the customary age (day 22) or 7 days earleir (day 15). If maternal separation took place on day 22, subsequent restraint on day 30 has no effect on the amount of time spend in sleep or on body temperature, relative to a comparison sgroup of unrestrained rats. But if maternal separation took place on day 15, restraint on day 30 elicits a marked initial increase in sleep and a later decrease in sleep and body temperature. The results are consistent with the interpretation that premature maternal separation retards the normal maturation of these behavioral and thermoregulatory responses to restraint stress.

Age Factors↗
PubMed1978

Early maternal separation increases gastric ulcer risk in rats by producing a latent thermoregulatory disturbance.

Rat pups that are separated early from their mothers, at postnatal day 15, become hypothermic when subjected to physical restraint on postnatal day 30. Restraint of separated pups also elicits an unusually high incidence of gastric erosions, as well as insomnia and an increase in quiet wakefulness. If hypothermia during restraint is prevented, neither the erosions nor the behavioral responses occur. Rat pups separated at the customary age (postnatal day 22) do not become hypothermic during restraint, and the restraint of such pups is not associated with either gastric erosion or insomnia.

Animals↗
PubMed1978

Ultrasonic vocalization during social interaction and isolation in 2-weeek-old rats.

Two-week-old rats were found to emit very little ultrasound in their cage except during arrivals and departures of the mother, when average peak rates of approximately 1 ultrasonic pulse/rat/min were detected. However, when all pups except one were removed from the home cage, the remaining isolated pup emitted ultrasound at a mean rate of 12 pulses/min for at least 30 min. When young rats of this age were placed alone in an unfamiliar test area, the ultrasound pulse rate was approximately 25/min, whereas groups of 4 littermates in the same situation emitted only occasional ultrasonic pulses. If an isolated pup in the novel environment was allowed access to a single anesthetized littermate or mother this also significantly reduced the rate of ultrasound emission, whereas a warm clay model did not.

Animals↗
PubMed1978

Predisposition to gastric erosions in the rat: behavioral and nutritional effects of early maternal separation.

After early maternal deprivation (on postnatal day 15), the incidence of restraint-induced gastric erosions on day 30 increases to approximately 5 times that of rats separated at the customary (day 21) weaning age. These data suggest that factors in the mother-infant relationship during postnatal development in young rats can influence later susceptibility or resistance to gastric erosions. We present a series of experiments to test whether loss of behavioral interaction with the mother or loss of maternal milk results in this increase in gastric erosion susceptibility. The results show that the absence of maternal milk, rather than behavioral deprivation, is primarily responsible for the increase in susceptibility after early maternal separation. However, behavioral interaction with the mother can additionally modify this susceptibility.

Age Factors↗
PubMed1977

Some effects of a split litter cross foster design applied to 15 day old rat pups.

Rat litters were divided and cross fostered on a postnatal Day 15 so that each mother had 4 of her own pups and 4 pups of a second litter, until weaning at 21 days. Daily weight and body temperature measurements made between Day 15 and 21 showed no differences between foster pups and pups who stayed with their biological mothers. However, by the age of 30 days, foster pups weighed less than pups reared by their own (biological) mothers; and foster pups at that age did not survive food deprivation as well as the pups reared by their biological mothers. In their Day 30 weights and the capacity to survive food deprivation, foster pups resembled pups that had been permanently separated from their mothers on postnatal Day 15. We conclude that the split cross foster design may introduce variability rather than reduce it. Nonetheless, this design may be useful in the experimental investigation of maternal behavior and mother-pup interactions in the rat.

Animals↗
PubMed1976

The organization of sleep and wakefulness after maternal separation in young rats.

Two-week-old infant rats were studied before and after 24 hr of maternal absence. This experience produced an increase in time spent awake, a reduction in time spent in paradoxical sleep (PS), and an increased frequency of state transitions with more frequent and shorter periods of both slow-wave sleep (SWS) AND PS. Body movements were increased and nonnutritive sucking decreased during PS after separation. Other aspects of sleep organization were relativly stable: the pattern of probability of direction of state transitions, the integration of the physiological and behavioral determinants of state, the pattern and amount of nonnutritive sucking, and the underlying PS cycle period. These findings, and the results of 2 control experiments, suggest that some aspects of the prolonged absence of the mother produce a shift in the infant's central neutral state regulation through processes yet to be understood.

Animals↗
PubMed1976

Olfactory denervation: its biological and behavioral effects in infant rats.

Two-week-old infant rats were treated with intranasal ZnSO4 and compared with littlemate controls 24 hr later. When infants were returned to their mother and littermates, those with olfactory deficits lost weight, had reduced cardiac and respiratory rates and lower body temperatures, and showed increased locomotor behavior in an unfamiliar test area. Subsequent experiments showed that in the absence of the mother and also in isolation, differences between ZnSO4-treated and control infants involved fewer systems were less marked, and presented different patterns. Isolated infants given oral ZnSO4 did not differ from controls on any measures. Olfactory denervation appears to produce these effects by disrupting nursing, by altering littermate interaction, and by other central nervous system effects that are independent of social interaction.

Animals↗
PubMed1975

Survival and recovery of physiologic functions after early maternal separation in rats.

Fourteen-day-old rats separated from their mothers have greatly increased survival rates, if provided with a local heat source. Body weight, temperature, cardiac and respiratory rates declined for 3 days in all separated animals, and eye opening was delayed most in those separated at room temperature. In survivors, a second phase followed in which all measures rebounded to levels characteristic of normally mothered infants. Cardiac rate, having fallen 40 percent in the first days after separation, rose to levels higher than normally mothered infants at 21 and 30 days of age. Recovery was not clearly initiated by any singly system studied, although non-survivors showed greater weight and temperature loss and evidence of gross motor deficit during the separation response phase.

Animals↗