Search

In rats, suckling elicits kyphosis—the bilaterally symmetrical, upright, humpbacked nursing posture—and maximal expression of the immediate early gene c-fos in a region of the caudal periaqueductal gray (cPAG) that mediates the sensorimotor integration of kyphosis. We determined the effects of prepartum unilateral nipple removal on nursing behavior and c-fos expression during a 60-min mother–litter interaction on Day 7 postpartum. Compared with dams suckled by 6 pups bilaterally, dams suckled unilaterally displayed essentially normal maternal behaviors, including kyphosis. Unilaterally suckled dams, however, showed an increase in the abnormal prone nursing posture, a decrease in proportion of kyphotic nursing of total time over pups, and a 20% higher contralateral/ipsilateral ratio of cPAG neurons expressing c-fos. These results are consistent with an incompletely lateralized neural pathway conveying suckling stimulation to the cPAG and provide a mechanism whereby kyphosis is elicited by unilateral suckling when pups initiate nursing from their supine dam. © 1999 John Wiley & Sons, Inc. Dev Psychobiol 35: 264–275, 1999 [ABSTRACT FROM AUTHOR]

Maternal behavior (retrieving, crouching, and licking) was induced in Sprague-Dawley virgin female rats by constant exposure to pups aged 1-2, 3-4, 5-6, 7-8, 9-10, 11-12, 13-14, or 15-16 days. The incidence of spontaneous components of maternal behavior, notably retrieving, was greater towards pups 1-8 days of age than towards older pups, whereas the occurrence of cannibalism did not differ as a function of pup age. With pups 1-2 through 13-14 days, the latency to onset of full maternal behavior was shortest with 1-2-day-old pups (2-day median) and longest with 13-14-day- old pups (7-day median). Females exposed to pups aged 3-4 through 11-12 days did not differ significantly in their latencies, the medians of which ranged from 4.0 to 5.5 days. Only 1 female out of 8 exposed to pups aged 15-16 days became fully maternal, but 5 more displayed components of maternal responsiveness. The optimal nature of neonates and the general attractiveness of a wider range of pup ages as stimuli for the elicitation of maternal behavior in rats, as well as comparisons to mice and hamsters, were discussed. [ABSTRACT FROM AUTHOR]

Offspring provide mothers with stimuli that impel their own nurturance. In rats, distal sensory stimuli from pups—sight, sound, odor—contribute to contact-seeking, whereas tactile stimuli from pups to dam's snout and ventrum elicit essential maternal behavioral reflexes involved in retrieval, licking, and the quiescent, upright nursing posture (kyphosis) . Brain sites involved with maternal behavior—assessed by lesions, immunocytochemical visualization of gene activity, and neurophysiological mapping—include the midbrain central gray, medial preoptic nucleus, limbic system, and somatosensory cortex; these may change with experience. Human mothers inadvertantly learn to identify their own baby rapidly after birth and can do so via a single sensory modality. Subsequent maternal responsiveness and gratification are impaired by inappropriate, insufficient, or nonreciprocal interactions such as occurs when the baby cries excessively, is blind, deaf, or autistic. Thus, maternal behavior characterized by elicited responses and emotional reactions to stimuli from offspring may be evolutionarily conserved. ©1997 John Wiley & Sons, Inc. Dev Psychobiol 31: 19–37, 1997 [ABSTRACT FROM AUTHOR]

In lactating rats, upper snout desensitization by trigeminal denervation severely impairs maternal behavior, with substantial recovery 12–24 hr later. The potential effects of interaction with pups on this recovery was investigated. Dams were subjected to bilateral infraorbital denervation or sham surgery on Day 5 postpartum and observed for 30 min with 6 foster pups 24 hr later, after separation from pups for 4 or 24 hr. Long separation reduced likelihood of retrieval and nursing behavior, infraorbital denervation reduced duration of pup licking, and these deprivations combined greatly increased latencies of pup sniffing and durations of facial self-grooming. Both conditions, and especially their combination, prolonged retrieval duration, the retrieval sequence being interrupted by other pup contact, such as licking. Thus, interaction with pups and adequate trigeminal stimulation maintain normal maternal behavior. These findings are possibly relevant to the normal decline of maternal responsiveness during late lactation and to other lesion-induced deficits. © 1997 John Wiley & Sons, Inc. Dev Psychobiol 30: 115–126, 1997 [ABSTRACT FROM AUTHOR]