Ventral trunk somatosensory determinants of nursing behavior in Norway rats: 2. Role of nipple and surrounding sensations

Abstract

By manipulating the quality and quantity of pups, Stern and Johnson (1990) showed that ventral trunk stimulation from rooting and suckling pups elicits nursing behavior in lactating Norway rats by causing the dam to become immobile (low crouch) and to ventroflex, resulting in a high crouch. In the present study, the dams were manipulated, but the litters were not. Experimental treatments consisted of prepartum nipple removal, local anesthesia of all 12 nipples, with or without anesthesia of four abdominal sites without nipples (both of which blocked cutaneous sensitivity and milk ejection). Compared with that of controls, the maternal behavior of experimental dams was characterized by normal retrieval and licking of pups, increases in various active behaviors, and deficient nursing, that is, <50% of them became immobile, briefly, and none displayed the high-crouch posture. Therefore, a full litter of capable pups cannot effectively stimulate nursing behavior in dams without nipples or in dams with their nipples and surrounding skin anesthetized. © 1992, Psychonomic Society, Inc.. All rights reserved.