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Biomedical subjects

M B Hennessy

Publications and source records attributed to M B Hennessy.

At least 55 records · Page 3Linked to original sources
PubMed1987

Cortisol and behavioral responses to separation in mother and infant guinea pigs.

In Experiment 1, lactating guinea pigs 3 days postpartum exhibited an elevation of plasma levels of cortisol when their litters were taken from the home cage and placed out of auditory range for 30 min. If pups were left within auditory range during the period of separation, or if the litter was disturbed but not removed, no increase in plasma cortisol levels was observed. In Experiment 2, 11/12- and 18/19-day-old guinea pig pups placed alone in a novel environment for 30 min displayed levels of plasma cortisol and vocalizations that were greater than those of pups tested in the same environment but with their mother. Pups tested with littermates but not with their mother exhibited plasma cortisol levels that were as great as those of pups tested alone. Pups tested with littermates vocalized much less than pups tested alone but more than pups tested with their mother. These results indicate that brief mother-infant separation can activate the pituitary-adrenal system in mother as well as infant guinea pigs and they provide further evidence for the existence of a reciprocal mother-infant attachment in this species.

Animals↗
PubMed1987

Nonedible material elicits chewing and reduces the plasma corticosterone response during novelty exposure in mice.

Mice placed into novel cages showed elevations of plasma levels of corticosterone. This response was of greater magnitude when the more novel of two cages was used. When mice had a piece of aluminum foil or cardboard available in the novel cages, they avidly chewed these substances. In the high novelty cage, the presence of either foil or cardboard reduced the magnitude of the plasma corticosterone response at 30 and 60 min. Mice exposed to novel cages for 30 min on each of 6 consecutive days showed a decline in chewing across days, although chewing still occurred during the last exposure. The plasma corticosterone response increased from the first to the sixth day of exposure, although the availability of foil in the high novelty cage reduced this response across days. The availability of a highly palatable food (peanut butter chips) evoked little chewing in the high novelty cage and had no effect on the plasma corticosterone response at 60 min. The results suggest that the chewing of nonedible substances can reduce the response of the pituitary-adrenal system to novelty and may therefore serve as an arousal-regulating mechanism in this species.

Animals↗
PubMed1986

Multiple, brief maternal separations in the squirrel monkey: changes in hormonal and behavioral responsiveness.

Infant squirrel monkeys had their mother removed from the home cage for 2 hr on 80 occasions between 12 and 31 weeks of age. The initial separation elicited high levels of infant vocalizations. By the second observation session (Separation 14), no vocal response to separation was observed. Plasma cortisol levels were markedly elevated at the beginning of the separation series, and there was a significant decline in this response by Separation 28, which was the next separation during which cortisol was monitored. However, there was no further decline, so that significant cortisol elevations were observed throughout the remainder of the separation series. At 35 weeks, the infants were separated one additional time and their responses were compared to those of a previously nonseparated control group. The control group vocalized more, but the two groups exhibited equivalent cortisol elevations. Observations of time spent riding on the mother during undisturbed conditions indicated that both groups developed independence from the mother at about the normal rate. Overall, the data show that brief separation from the mother can activate the infants' pituitary-adrenal system even when the infant has been separated 80 times previously, no longer appears behaviorally responsive to separation, is almost 9 months of age, and exhibits normal signs of independence from the mother.

Animals↗
PubMed1986

Effects of social partners on pituitary-adrenal activity during novelty exposure in adult female squirrel monkeys.

Adult female squirrel monkeys from established social groups were exposed to novel surroundings either while alone or while with an adult female partner. The partner was either familiar and judged to be affiliative with the subject, familiar and not judged to be affiliative with the subject, or unfamiliar. The females' plasma cortisol levels were higher at the end of the 25th hr of exposure than at the end of the first hr when the females were alone or with a familiar partner, but not when they were with an unfamiliar partner. In no instance were cortisol concentrations greater when females were tested alone than when they were tested in the presence of a companion. Behavioral signs of distress were greater during the first as compared to the 25th hr of exposure and showed no influence of the presence of a partner. Contact/proximity between monkeys was greater during the 25th than during the first hour of exposure in the familiar partner judged to be affiliative and in the unfamiliar partner conditions. These results contrast with those of studies investigating the disruption of the mother-infant relationship in squirrel monkeys, and provide further evidence that the pituitary-adrenal system of these animals is not responsive to the disruption of adult social relationships.

Adrenal Glands↗
PubMed1986

Maternal separation alters later consumption of novel liquids in the squirrel monkey.

The consumption of novel, fruit-flavored drinks was measured in juvenile squirrel monkeys that had either had their mother removed from the home cage for 2 h on 80 occasions prior to weaning or had not undergone this separation procedure. Among previously separated animals, males drank more than did females during the first 30 min following presentation, whereas there was no difference in the drinking of nonseparated males and females at this time. Further, the amount of liquid consumed during the 20 h following presentation increased across days of exposure in the nonseparated, but not in the previously separated monkeys. These results show that brief maternal separation can affect the later behavior of squirrel monkeys, and are consistent with findings in rhesus macaques that maternal separation alters later exploratory behavior.

Animals↗
PubMed1985

Social and environmental factors influencing mother-infant separation-reunion in squirrel monkeys.

Sixteen squirrel monkey mother and infant dyads were housed in groups of two. They were separated and then immediately reunited in their familiar home cage or in a novel environment, either in conjunction with the second mother-infant dyad, or as a single manipulated pair. Behavioral observations of both dyads were made during the 30-min period following these manipulations; blood samples were then taken for cortisol assay. Mothers' locomotor activity increased when a single dyad was manipulated in the home cage and decreased in the novel environment where proximity between the pairs increased. Cortisol levels varied significantly across conditions, with mothers and infants responding to different stimuli. Mothers responded primarily to social disruption, including separation from the other dyad, and infants responded most clearly to novelty and separation from the other dyad. No significant differences were observed over base levels when both mother and infant pairs were reunited in the home cage, indicating that changes were not due to the disturbance involved in the separation procedure.

Animals↗
PubMed1984

Effects of social experience on the corticosterone response of adult rats to pup cues.

Rat mothers whose pups have been removed show greater plasma corticosterone elevations when the pups are shocked and returned in a wire-mesh basket than when only the wire basket is returned. For mothers housed with an adult male or virgin female, this differential adrenocorticoid responsiveness between the shocked-pup and empty-basket conditions was not observed unless the adult partner was removed 18 hr before testing. Nonlactating adults housed with pups and mother for up to 2 weeks exhibited corticoid elevations equivalent to the shocked-pup and empty-basket conditions whether tested with the mother or 18 hr after her removal. These results indicate that the differential pituitary-adrenal responsiveness that female rats show to pup cues during lactation cannot be accounted for by the length of the mother's exposure to pups, and, further, that this relative responsiveness during lactation appears to be largely due to the suppression of adrenocorticoid reactivity to a nonsocial environmental disturbance.

Animals↗
PubMed1984

Presence of companion moderates arousal of monkeys with restricted social experience.

Squirrel monkeys were reared on inanimate maternal surrogates in individual cages. The surrogates were removed at 8 months, and at approximately 1 year of age each animal was paired with a similarly-reared peer for 4 weeks prior to testing. When placed in a novel environment for 30 min, the juveniles emitted significantly more high-pitched vocalizations and were significantly more active when tested alone than they were when tested in the presence of their cagemates. A significant elevation of plasma cortisol over resting levels was observed only when animals were exposed to the novel environment alone. Separation from the peer in familiar surroundings had no effect on any measure. These results indicate that the capacity to use social partners to moderate arousal can develop in squirrel monkeys raised from shortly after birth without a mother or physical interaction with other conspecifics, and with relatively little social experience overall.

Animals↗
PubMed1982

Influence of the maternal surrogate on pituitary-adrenal activity and behavior of infant squirrel monkeys.

Squirrel monkey infants reared on surrogates showed an increase in vocalizations, but no change in plasma cortisol levels when the surrogate was removed from the home cage for .5 hr. When the infant was exposed to novelty during separation, there was a further increase in vocalizations, as well as increases in movement and plasma cortisol. Placing the surrogate with the infant in the novel environment reduced the behavioral reaction and led to high levels of infant-surrogate contact; however, plasma cortisol levels were as high at .5 hr as when the infant was in the novel environment alone. With longer (2-4 hr) exposures to the novel room, cortisol elevations were attenuated by the presence of the surrogate. When the infant was alone, levels of cortisol, but not protest behavior, increased with length of exposure to the novel room. These results indicate that the physiological reaction to separation procedures in infant primates may not be safely inferred from behavioral responses, and, together with earlier findings, suggest a deficiency in the attachment of surrogate-reared infants.

Animals↗
PubMed1982

Oral ethanol intake nad levels of blood alcohol in the squirrel monkey.

Oral alcohol ingestion and blood alcohol levels were examined in adult female squirrel monkeys to assess the feasibility of using this primate as a model for fetal alcohol effects. In one experiment, alcohol intake was evaluated in nonpregnant animals under conditions in which the concentration of ethanol, length of ethanol exposure, and degree of liquid deprivation were varied. In another experiment blood alcohol levels were measured in pregnant animals of two subtypes that had been drinking ethanol. In a third experiment, time-dependent blood alcohol levels and behavior were evaluated in nonpregnant monkeys following intubation of specific doses of ethanol. Results showed that nonpregnant monkeys drank ethanol at concentrations of 5 to 10%, and that the amount of ethanol consumed was related to the concentration and length of time ethanol was available. When given access to a 5% ethanol solution, pregnant animals drank quantities that varied between individuals and subtypes, with maximum blood levels, measured up to 6 hr after presentation, ranging from 1 to 196 mg%. Intubation of ethanol resulted in blood alcohol levels and incoordination scores that were linearly related to dose, with maximum effects occurring 1 hr after administration. Elimination of ethanol from the blood at levels above 50 mg% occurred at a rate of about 35 mg%/hr, while the rate of clearance from the body was calculated to be approximately 250 mg/kg/hr.

Alcohol Drinking↗
PubMed1980

Infant responsiveness to maternal cues in mice of 2 inbred lines.

The present study examined the responsiveness of 19- and 20-day-old C57BL/6J (C) and A/J (A) mouse pups to maternal cues. The C pups were found to spend more time near their C or A foster mother than they did near a virgin female. The A pups showed no such preference. Attempts to increase the motivation of A pups to approach the mother did not produce any preference for maternal cues, However, when the bedding on which odorous substances had been permitted to accumulate for an extended period of time was used as choice stimuli, pups of both lines showed a preference for the bedding of the mother as opposed to that of a virgin female. These results support findings with other rodents of a change in the female's odor during lactation which increases her attractiveness to her pups; and they demonstrate a genetic difference between pups of 2 inbred strains in their approach to maternal cues.

Animals↗
PubMed1980

Maternal behavior, pup vocalizations, and pup temperature changes following handling in mice of 2 inbred strains.

A cross-fostering design was used to examine maternal behavior, pup vocalizations, and pup temperature changes following an infantile procedure in C57BL/6J (C) and A/J (A) mice. In Experiment I, maternal behavior of C and A mothers after infantile handling differed in a number of ways irrespective of the strain of the foster pups. In addition, A pups were retrieved faster but licked less than were C pups by mothers of both strains. Handling appeared to increase the probability that strain differences would occur in that no differences between the lines, in either the behavior of the mothers or the capacity of the pups to elicit maternal behavior, were found during observations made just prior to daily handling. These observations also revealed that mothers of both strains treated same-strain foster pups differently than they treated foster pups of another strain. In Experiment II, A pups were found to emit more ultrasound following handling than were C pups, suggesting that retrieval but not pup-licking was stimulated by ultrasonic signals. Measurement of pup temperature during and following the handling procedure showed that (1) strain differences in ultrasonic signaling were not related to strain differences in the degree of hypothermia experienced by the pups; (2) recovery of body temperature following handling was slow for pups of both strains, and depended to some degree on the strain of the pups' foster mother; and (3) development of thermoregulation occurred more rapidly in C than A pups.

Animals↗
PubMed1980

Altered plasma corticosterone responses during lactation in mice of two inbred strains.

Plasma corticosterone levels during lactation were examined in inbred A/J (A) and C57BL/6J (C) mice. Following shock, lactating A females showed a diminished corticosterone response relative to nonlactating controls on day 5 of lactation, but not on day 12. In contrast, plasma corticosterone levels of lactating C females 5 and 15 min following shock were lower than those of controls on day 12, but not on day 5. Consistent with these findings, lactating A females had significantly lower plasma levels of corticosterone 15 min following nonnociceptive treatments (involving distrubance, exposure to novelty, and pup manipulation) when tested on day 5 then they did when tested on day 12, whereas lactating C females had lower levels on day 12 than on day 5. Lactating females of each strain showed the same response to shock on day 12 if they reared A pups as they did if they reared C pups. This indicates that the difference found between the strains on day 12 was due to a difference in some property of A and C mothers, rather than to a difference in a characteristic, such as suckling patterns, of the pups of the two strains. It was also found that at long intervals following shock (45 and 90 min) 5-day lactating C females had higher levels of plasma corticosterone than did controls. There was no effect of lactation on resting adrenocorticoid levels in A or C females at either 5 or 12 days. The results indicate that laboratory mice show changes in hypothalamo-pituitary-adrenal activity during lactation which both vary with strain of the mother, and differ in several respects from those previously reported for rats.

Animals↗