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J R Alberts

Publications and source records attributed to J R Alberts.

At least 73 records · Page 4Linked to original sources
PubMed1985

Milk availability modulates weaning in the Norway rat (Rattus norvegicus).

Two experiments were conducted to investigate the role of milk availability in the development of independent feeding and drinking in the Norway rat pup. Beginning on Day 14 postnatally, pups were exposed to different levels of milk supply by changing litter size from 8 to 4 versus 12 pups (Experiment 1) or limiting temporally the pups' access to a lactating dam to 8, 14, or 24 hr daily (Experiment 2). Both manipulations accelerated weaning in milk-poor pups in comparison with same-age pups with relatively greater milk supplies. By adding solid food and water to their diet, early weaning pups compensated for the negative energy consequences of milk reduction and achieved premanipulation growth rates. Milk availability thus appears to affect weaning, and it is suggested that the developmental changes in the nutritive energy balance between mother and offspring contribute to the emergence of independent ingestion.

Animals↗
PubMed1984

Nonnutritive, thermotactile induction of filial huddling in rat pups.

Norway rat pups, 15 days of age and older, huddle preferentially with members of their own species. This normal filial response can be reassigned, however, by altering the olfactory characteristics of the mother. The present series of experiments was designed to isolate those aspects of maternal stimulation that establish the filial huddling preferences of rat pups. Results of two-choice huddling tests indicated that daily, 4-hr exposures to a perfumed foster dam induced filial preferences for odors associated with maternal care. Similar effects were also achieved with equal amounts of "mere exposure" (familiarization) to odors. Different kinds of odor-experience pairings were evaluated with a within-subject regime of alternating, daily exposures. It was found that preferences induced by maternal contact are stronger than those resulting from familiarization. We rejected the hypothesis that the nursing relationship is a necessary or contributory factor in the establishment of the rat's filial attraction; preferences for odors associated with a nonlactating foster mother were as strong as those derived from maternal contact that included nutritive nursing. Contact interactions with an inanimate, warm, scented tube induced preferences as strong as those induced by maternal care. It was concluded that thermotactile stimulation during mother-young interactions induces olfactory preferences in the weanling rat.

Animals↗
PubMed1984

A specialization of taste aversion learning during suckling and its weaning-associated transformation.

During ontogenesis, altricial mammals advance through different ecological niches which require correspondingly different adaptive strategies. We view learning as an important feature of ontogenetic adaptations and consider the acquisition and expression of taste aversion learning during nursing within this framework. Fifteen-day-old preweanling rat pups fail to acquire conditioned taste aversions while nursing, whereas 20-day-old weanlings readily learn flavor aversions while suckling (Martin & Alberts, 1979). The developmental emergence of taste aversion learning while nursing coincides with reduction in maternal milk supply and the rat pup's transition to a solid food diet. We considered the ontogenetic transformation of learning while nursing as a feeding-related adaptive strategy of the weanling rat and tested two predictions derived from this view: (1) delayed weaning might postpone acquisition or expression of suckling-related taste aversions and (2) conditions that permit weaning (e.g., access to alternate food sources) might induce acquisition or expression of such taste aversions. Both predictions were confirmed.

Animals↗
PubMed1983

Maternal licking of young: resource exchange and proximate controls.

Rat mothers lick the anogenital area of their young, stimulate reflexive urination, and ingest the urine. To quantify the transfer of body water from offspring to mother, we injected 5- to 30-day-old rat pups with tritiated water and the next day measured the radioactive label in maternal plasma. Rat dams reclaim about 16 ml of water/day from 5-day-old litters, 20 ml/day from 10-day-olds, and 40 ml/day from 15-day-olds. Urine consumption decreases to negligible amounts by Day 30. Time-lapse video recordings were used to measure maternal anogenital licking from Days 1-31 postpartum. Water transfer correlated with the developmental diminution of maternal anogenital licking. Maternal anogenital licking is controlled, in part, by the transfer of water from litter to dam and by the mother's salt appetite. Anogenital licking of pups was decreased after dams ingested a 0.15 M solution of NaCl but not after consumption of KCl, implicating a sodium specific mechanism. Licking of other regions of the pup's body was not affected. We discuss mother-infant interactions in terms of bidirectional exchanges of resources that constitute a "symbiotic" association.

Animals↗
PubMed1982

Associative learning in neonatal rats revealed by cardiac response patterns.

Infant rat pups (3-4 days of age) that received a single pairing of a novel odor (CS) with illness later responded to the CS with sustained accelerations in heart rate (HR); a different novel odor evoked deceleratory HR responses. Control pups responded to the CS and the second novel odor with cardiac deceleration. In a second experiment, rat pups that received three pairings of a novel odor with a cold (10 degrees C) temperature reinforcement displayed a similar pattern of HR responses, i.e., acceleration to the CS and deceleration to the novel odor. Cardiac response patterns are a useful measure of learning in infant mammals. The directional modulations of HR found in these experiments compare favorably with previous interpretations of "orienting" and "defensive" reactions derived from studies of HR responses in humans.

Animals↗
PubMed1981

Physiological and behavioral consequences in rats of water recycling during lactation.

Radioactive water injected into 10-day-old rats were recovered the following day from their mothers' blood. This transfer of water was nearly eliminated by ligating the injected pups' urethras, a result indicating that mother rats consume their offspring's urine. Preventing urine consumption by ligating urethras of all pups in a litter doubled the plasma volume deficit in dams produced by 24 hr of water deprivation alone and led to increased isotonic saline, but not water, intakes following after water deprivation. Mother rats' daily water intakes increased after they were deprived of pup urine, and their pup-licking behavior increased following water deprivation. These findings indicate that urine consumption by mother rats has both physiological and behavioral consequences and suggest that pup licking is, in part, an ingestive behavior.

Animals↗
PubMed1980

The first foray: maternal influences in nest egression in the weanling rat.

A series of experiments was performed to examine the determinants of the rat pups' 1st excursions from the maternal nest into the novel environment outside the burrow. A standardized, nidic environment consisting of a maternal nest and adjoining open field was studied under a variety of structured test conditions. When the mother was outside the nest, pups readily ventured into the field. The early excursions were not stimulated by the mother's absence from the nest because when the mother was removed from the nest but not placed in the field the pups remained nestbound. Anesthetized dams elicited few excursions, suggesting that olfactory cues are less potent in this situation than behaviorally transmitted signals. Nonlactating adults were not attractive to pups but after induction of "maternal responsiveness" concaveated males facilitated egression. The data from a final experiment suggest that when in the nest, the dam stimulates egression by providing additional "permissive" stimuli that render the weanling more responsive to approach cues outside the nest.

Animals↗
PubMed1979

Taste aversions to mother's milk: the age-related role of nursing in acquisition and expression of a learned association.

The development of taste aversion learning to novel cues contained in mother's milk was examined in rat pups. Pups receiving distinctive mild by experimenter-delivered oral infusions followed by toxicosis formed an aversion to the dam's diet. Robust aversions were learned as early as Day 10 and were retained for at least 11 days. When the same distinctive milk was obtained directly from a foster mother through nursing, however, only weanling-age pups (over 20 days) formed an aversion. X-ray analysis of nipple location in the mouths of suckling pups suggested that pups between the ages of 10 and 21 days receive milk at a similar tongue locus. Flavored milk was then delivered at specific time intervals in controlled quantities through tongue cannulas implanted at loci corresponding to the nipple position shown by the X-rays. Cannulated preweanling pups that were attached to a nipple during milk delivery failed to associate the taste cue with illness, whereas both preweanlings off the nipple and weanlings on the nipple acquired aversions to the taste cue in the milk. The evidence obtained in these experiments suggests that pups of all ages are incapable of expressing a taste aversion in a nursing situation and that preweanling pups in particular are also dificient in acquiring aversions within a suckling context. The inability of preweanling pups to acquire taste aversions in a nursing situation appears to result from a failure to associate taste cues with illness rather than a failure to detect taste cues obtained from a nipple.

Age Factors↗
PubMed1979

Olfactory stimulation induces filial preferences for huddling in rat pups.

Rat pups of all ages huddle with conspecifics, but the senosory control of contact behavior changes ontogenetically. Thermal cues control huddling until about Day 15, at which time species' odors become the dominant stimulus. The present experiments indicate that the filial response to conspecifics is dependent on olfactory experience. A synthetic chemical scent was added to the smells of the dam from Day 1 to Day 20 postpartum. Standardized videographic tests were used to assess the development of huddling preference. Preferences for nest-typical smells emerged by Day 15 in pups from both scented and nonscented litters. Pups from scented nests preferred to huddle with a scented stimulus rat, whereas control pups preferred a nonadulterated rat stimulus. Additional testing indicated that the affiliative preferences were specific to rearing odor and were not based on decreased aversion to test scents, or on disrupted olfactory discrimination. The ontogeny of species-typical contact behavior is discussed in terms of the induction of a perceptual preference that is based on early odor stimulation.

Animals↗
PubMed1978

Huddling by rat pups: multisensory control of contact behavior.

Huddling, or clumping behavior, begins in the litter situation and persists throughout the adult life of the rat (Rattus norvegicus). In pups, as in adults, the behavior provides a metabolically important means of reducing heat loss. The sensory stimuli that elicit, direct, and maintain huddling in developing rat pups (5-20 days of age) were studied in a standardized testing situation by using long-term time-lapse video observations. All pups huddled with a single, immobile sibling. A loop of warm tubing also elicited huddline. However, it appears that other, nonthermal cues can elicit huddling, since a dead, ambient-temperature pup was a sufficient stimulus for the behavior. Disruption of normal olfactory input by intranasal infusion of zinc sulfate interfered with the maintenance of contact. In addition, two kinds of tactile stimulus, vertical contours and furry "comfort" cues, as well as photic responses appeared to participate in the mediation of huddling. Huddling in the altricial rat is under multisensory control, although the number of cues used by pups for huddling appears to increase with age.

Age Factors↗
PubMed1978

Huddling by rat pups: group behavioral mechanisms of temperature regulation and energy conservation.

Body heat loss was attenuated and oxygen consumption was reduced by huddling in litters of developing rats. Rat pups derive physiological benefits from huddling similar to those enjoyed by adult mammals; these findings contrast with previous characterization of the altricial rat as poikilothermic. Huddling insulates by lessening the explosed body surface area of the participants, thus retarding heat loss and enhancing the efficiency of thermogenesis. These physical mechanisms of the clump are actively regulated by the pups. A novel quantitative measure of huddle size revealed a form of group regulatory behavior in rat pups whereby the surface expanded and contracted with increases and decreases in ambient temperature. The individual basis of this group regulatory activity was investigated by marking individual pups and observing them in huddles by means of time-lapse videography. It was found that individual animals circulate throught the huddle, frequently exchanging locations in the group. By studying the huddle positions of an anesthetized pup and a marked control sibling, dynamics of the pup flow were clarified. Ordinarily, the direction of movement was actively downward, into the pile; immobile pups "floated" on the surface. When the nest temperature was raised to thermoneutral, the direction of pup flow reversed and an immobile animal sank to the depths of the huddle. Through individual competitive adjustments the huddle behaves as a self-regulating unit which provides warmth and insulation to all its active members.

Age Factors↗
PubMed1978

Ontogeny of thermal and olfactory determinants of huddling in the rat.

In standardized tests of huddling behavior, 5-, 10-, 15-, and 20-day-old rat pups spent substantial and equivalent amounts of time with an immobile rat or a heated, fur-covered tube, which suggests that the conspecific and inanimate stimuli were equally attractive to the pups. Two-choice preferences tests, however, revealed dramatic developmental differences in attraction. Younger pups preferred to huddle with the warmer, inanimate target, whereas older pups preferred the conspecific. The emergent conspecific preference appears mediated by attraction to species odors. The 5- and 10-day-olds huddled equally with an immobile rat and an immobile gerbil, stimuli with similar thermal and tactile properties, but older pups preferred the conspecific. Intranasal zinc sulfate treatment eliminated preference for the conspecific in 15- and 20-day-olds but did not disrupt huddling per se. Thermal cues were sufficient to elicit huddling at all ages, but olfactory cues became a more salient influence before weaning. An ontogenetic transition from "physiological" to "filial" huddling is discussed in terms of changes in sensory control of early behavior.

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