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Biomedical subjects

M A Hofer

Publications and source records attributed to M A Hofer.

At least 73 records · Page 4Linked to original sources
PubMed1986

Role of carotid sinus and aortic nerves in respiratory control of infant rats.

The roles of carotid sinus (CSN) and aortic depressor nerves (ADN) in the maintenance of rhythmic respiration and in the response to airway occlusion were investigated in 8- to 10-day-old infant rats. Cutting the CSN led to a periodic loss of rhythmic respiration with arrhythmic low-amplitude waveforms, frequent end-expiratory pauses, and occasional apneas observed in unanesthetized unrestrained pups studied in their home cage nests by impedance pneumography. Cutting the ADN alone did not have this effect. Sinoaortic denervation (SAD) in which both nerves were cut, produced a more severe disturbance that was not relieved by tracheostomy, indicating that it was not due to upper airway obstruction. Tracheal pressure recordings from anesthetized SAD infants in response to short periods of external airway obstruction showed reduced respiratory efforts and prolonged recovery times, deficits that may play a role in the mortality previously reported after SAD in infant rats.

Airway Obstruction↗
PubMed1985

Development of maternal behaviors in prepubertal rats at three ages: age-characteristic patterns of responses.

Individual 18-, 24-, or 30-day-old male and female Wistar prepubertal rats (juveniles) were continuously exposed to 3-8-day old pups in order to determine developmental differences in the expression of maternal and other behaviors during the process of sensitization. The results that emerged from this study are as follows: Maternal behaviors are neither consistent nor integrated in their expression prepubertally; exposure to pups facilitates the emergence of some maternal behaviors in juveniles more easily than others, e.g., retrieving and anogenital licking more than ventral crouching or nestbuilding; there are age-related differences in the expression of different maternal behaviors, e.g., 24-day-olds retrieve more than at other ages; in our strain, few, if any, gender differences are apparent in the expression of maternal behaviors prepubertally; juvenile play behaviors (charge, pounce) are related to retrieving behavior in the context of exposure to pups. Overall, the results suggest that maternal behaviors are distinct developmentally and probably involve different mechanisms in prepubertal animals.

Age Factors↗
PubMed1985

Sleep-wake state organization in infant rats with episodic respiratory disturbance following sinoaortic denervation.

The role of arterial chemoreceptors in the maintenance of rhythmic respiration during sleep was investigated in 2-week-old rats by microsurgical sectioning of carotid sinus and aortic depressor nerve fibers (SAD) and later recording of respiratory pattern by impedance pneumography and sleep-wake states by electrophysiological methods. Deafferentation produced high rates of an atypical respiratory pattern characterized by episodes during which the usual pattern was replaced by an arrhythmic series of low amplitude waveforms with frequent short pauses and occasional gasps. These episodes lasted a mean of 20s, occurred 15.1 times/h and were virtually confined to the REM state. Apneas occurred in all stages of sleep and were not increased by SAD but were significantly associated with state changes only after denervation. Body movements were unchanged and sleep-wake state organization was only minimally affected by SAD. These results suggest that the REM state may constitute a vulnerable period for respiratory control in infancy during which afferent feedback from peripheral arterial chemoreceptors may ordinarily play a stabilizing role.

Afferent Pathways↗
PubMed1985

Nutrient control of cardiac rate in infant rats: role of arterial baroreceptors.

A surgical procedure is described for the deafferentation of carotid sinus (CS) and aortic depressor (AD) baroreceptors in 2-wk suckling rats. Baroreflex testing in unanesthetized pups showed that cardiac rate responses to acute elevations of blood pressure were reduced to less than 9% of controls after combined denervation (CSAD), 28% after AD and 47% after CS denervation at 4 h. After 24 h of nutrient deprivation, resting cardiac rates of sham operated controls fell a mean of -148 beat/min, significantly more than CS, AD, or CSAD groups (P less than 0.01). Baroreflex test responses in individuals correlated significantly with their later responses to nutrient deprivation (r = 0.67, P less than 0.01). There were no significant differences in base-line cardiac rate, systolic blood pressure, or cardiac rate during 24 h intragastric milk infusion between deafferented and control pups. These experiments suggest that arterial baroreceptors are important in the cardiovascular adjustments after nutrient deprivation in suckling rats.

Afferent Pathways↗
PubMed1984

Lethal respiratory disturbance in neonatal rats after arterial chemoreceptor denervation.

The role of afferent feedback from arterial chemoreceptors in the maintenance of rhythmic respiration during early development was studied by section of carotid sinus and aortic nerves of rat pups at different ages from 3 days to 3 weeks postnatally. This deafferentation produced a severe, episodic respiratory disturbance, limited to pups younger than 21 days and associated with mortality rates near 50% during the 2 weeks following surgery. These findings may have implications for the role of peripheral chemoreceptors in the periodic apneas of premature infants and in the Sudden Infant Death Syndrome.

Analysis of Variance↗
PubMed1984

The role of the accessory and main olfactory systems in maternal behavior of the primiparous rat.

The objective of this study was to analyze the respective roles of the main and accessory olfactory systems in the development of maternal behavior in the primiparous Wistar rat. Females underwent one of the following treatments: vomeronasal nerve section (VN), irrigation of nasal cavities with 5% ZnSO4 solution (ZN), surgical control, saline irrigation control, and normal control. Surgical or first irrigation were done before mating occurred. Irrigations were done every 7 days thereafter. The dams and their litters were observed from the day the litter was born (Day 1) through Day 16. Pup weights and temperatures were recorded daily. Home cages were checked daily for changes in nest location and number of times pups were found out of the nest. Retrieving tests were conducted on Days 4, 7, 10, and 13. The following behavioral items were observed: number of pup retrievals , number of times mother nosed or licked pups, percentage of litter returned to nest by end of test, dam self-grooming, dam climbing or rising, and dam digging or burrowing in shavings. The VN dams and their litters were not significantly different from the control dams and their litters on any of the measures taken. The ZN dams and their litters were not significantly different from their controls on all measures except for pup body temperature which was slightly lower from Day 13 through day 16 and pup body weight which was slightly lower from Day 12 through Day 16. Since these differences are very small, they do not seem to indicate a serious deficiency in maternal behavior. The results indicate that adequate maternal behavior develops with either of the two systems intact.

Animals↗
PubMed1984

Early stages in the organization of cardiovascular control.

Our studies have revealed a number of unexpected characteristics of the immature cardiovascular system of the infant rat. Sympathetic and parasympathetic divisions of the autonomic system appear to have different timetables for the development of tonic and phasic activities. These different timetables of development result in unusual physiological organizations at particular stages in postnatal life. We have described some of the features of one of these: the infant rat's cardiac rate responses in the second week after birth include a high resting rate, decreased rates in response to several (but not all) forms of activation, and two forms of phasic activity, a bradycardia and a tachycardia, that are related to naturally occurring behavioral states and have not been described in adults. The nature of this age-specific autonomic organization was explored further and found to be embedded in the infant's relationship with its mother and in her role as a supplier of nutrient in particular. The mechanisms by which nutrient intake regulates autonomic cardiovascular control during this stage of life have been partially explored by analytic experiments and the results are described along with the possible adaptive value of this regulatory system.

Afferent Pathways↗
PubMed1983

The effects of maternal deprivation and of refeeding on the blood pressure of infant rats.

Blood pressure regulation was explored in infant rats 12-14 days of age during the 30-40% changes in cardiac rate that accompany nutrient (maternal) deprivation and refeeding at this age. Using specially modified tail cuff and intraarterial cannulation techniques, blood pressure was found to be maintained at stable levels (65-75 mm Hg) throughout these marked changes in pumping rate. The results suggest that adrenergic vasoconstrictor tone is controlled reciprocally with heart rate during a complex cardiovascular response to changes in nutrient levels at this early age. The possible role of such a mechanism in the development of "spontaneous" hypertension is discussed.

Animals↗
PubMed1982

Control of sleep-wake states in the infant rat by features of the mother-infant relationship.

A series of experiments in 2 strains of Wistar rats explored which aspects of maternal separation were responsible for the sleep disturbance of the young. Neither their own mother, after mammary duct ligation, nor constant intragastric infusion of nutrient during the day of separation were found to ameliorate significantly the changes in sleep-wake state organization. However, a periodic nutrient delivery schedule and a formula closely resembling rat milk each ameliorated, and together entirely prevented, the sleep-wake disturbance. Decreased ambient temperature during separation tended to exaggerate the disturbance and periodic tactile-vestibular stimulation tended to reduce it. These findings suggest that the infant rat's normal sleep-wake pattern is maintained by the rhythmicity and composition of the milk delivered to it by its mother, although her warmth and behavioral interaction with it may play subsidiary roles. Separation produces its effects by removing these regulating features of the relationship.

Animals↗
PubMed1981

Effects of infraorbital nerve section on survival, growth, and suckling behaviors of developing rats.

Previous studies on sensory control of nursing in the rat have emphasized local olfactory cues. This study examined the role of tactile sensory processes by surgical section of the infraorbital nerve in rats at 17, 12, 7, and less than 1 day of postnatal age. All sectioned rats showed anesthesia of snout, upper lip, and vibrissal pads, and severe impairment of nipple attachment for at least the first day after denervation. Seven-day-old pups failed to recover, and all died after 3-6 days of relentless weight loss. Seventeen-day-old pups showed no weight loss after denervation if already weaned to solid food, but they lost weight for 3 days, and 25% failed to recover. Behavioral observations showed that denervated pups were activated by the mother's ventrum and probed for the nipple in the appropriate area but failed to focus head sweeping or licking and mouthing on the nipple itself and did not attach even when the nipple was inserted into the intact sensory areas of the mouth. Recovery after nerve section did not appear to be due to nerve regeneration. The data show that tactile cues are not necessary for normal nursing in the rat and suggest that important tactile sensorimotor adaptations may occur during the early and late phases of nursing.

Afferent Pathways↗
PubMed1980

Vertical transmission of acquired ulcer susceptibility in the rat.

Premature separation of rat pups from their dams greatly increases their susceptibility to restraint-induced gastric erosions. When prematurely separated female rats grow to adulthood and mate with stock males, their normally reared F 1 progeny also have increased susceptibility to restraint-induced erosions. Cross-fostering studies show that prenatal rather than postnatal factors transmit this susceptibility to the F 1 progeny.

Animals↗
PubMed1980

Sensory processes in the control of isolation-induced ultrasonic vocalization by 2-week-old rats.

The presence of a passive (anesthetized) littermate greatly reduced the ultrasonic vocalization of 2-wk-old rat pups placed suddenly in an unfamiliar test box, without affecting other behavior. Isolated pups maintained high levels of vocalization over the 6-min test period while rapidly reducing other behavioral activities. A series of experimental surrogate models allowed analysis of the sensory modalities necessary and sufficient for the littermate effect. Pups did not respond to a single cue or to a pattern of different modalities, but they gave graded responses to several sensory sensory modalities in a cumulative fashion. Extent of body contact and reduction of ultrasound were positively correlated across surrogates, but not across individuals in most conditions. Pups made anosmic with ZnSO4 did not reduce vocalization and continued to show high levels of body contact. Experiments manipulating the olfactory properties of the littermate, however, raised the question whether olfactory denervation exerted its effects by depriving the pup of cues or by secondary effects on arousal and/or motivational systems.

Animals↗
PubMed1980

Effects of reserpine and amphetamine on the development of hyperactivity in maternally deprived rat pups.

Maternal deprivation for 24 hr is known to produce hyperactivity in 2-week-old infant rats kept at nest temperature. Pretreatment with reserpine (0.5 mg/kg), at the time of separation, prevented the development of hyperactivity over the ensuing 24-hr, whereas the same dose in mothered littermates had no residual effects on behavior the next day. d-Amphetamine (0.25 and 2.0 mg/kg) produced dose-dependent increases in locomotion and rearing and decreases in self-grooming behavior, which were of comparable magnitude whether the pups were separated and kept warm, normally mothered, or separated at room temperature, a condition known to produce decreased activity levels. Cardiac rates were not affected by either drug; reserpine lowered respiratory rates slightly, amphetamine increased body temperature following behavior testing. Altered accumulation of catecholamines at presynaptic terminals is discussed as a possible neurochemical mechanism for behavior changes following maternal separation in this model system.

Animals↗