Functions of the caudal periaqueductal gray in lactating rats: Kyphosis, lordosis, maternal aggression, and fearfulness

Severe impairment of the kyphotic nursing posture in lactating rats found p reviously after prepartum lesions of the caudal intercollicular periaqueduc tal gray (cPAG-x) was confirmed and was extended to a continuous 24-hr peri od. Litters of cPAG-x dams gained similar to 10% less weight postnatally th an controls, which was in part related to their dams' compensatory prone nu rsing posture that was ineffective for milk letdown. Sexual proceptivity an d receptivity (lordosis) during the postpartum estrus were virtually elimin ated in subjects with relatively large bilateral cPAG lesions. The doubling of maternal attacks toward a male intruder after lesioning was also confir med and was related to reduced fearfulness in an elevated plus-maze. Thus, the cPAG plays a multifaceted role in parturient rats; it is involved in th e mediation of nursing, sexual, aggressive, and fear behaviors.