Effects of unilateral suckling on nursing behavior and c-fos activity in the caudal periaqueductal gray in rats.
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.
Lonstein
J S
JS
Department of Psychology, Rutgers University, New Brunswick, NJ 08903, USA.
Stern
J M
JM
D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal / Q000502:physiology; D002420:Cauda Equina / Q000502:physiology*; D002535:Cerebral Aqueduct / Q000502:physiology*; D005247:Feeding Behavior / Q000523:psychology*; D005260:Female; D016762:Genes, fos / Q000235:genetics*; D008297:Male; D008425:Maternal Behavior / Q000523:psychology; D008892:Milk; D009044:Motor Cortex / Q000502:physiology; D011187:Posture / Q000502:physiology*; D051381:Rats; D013003:Somatosensory Cortex / Q000502:physiology; D013391:Sucking Behavior / Q000502:physiology*