THE EFFECTS OF OLFACTORY AND SOMATOSENSORY DESENSITIZATION ON FOS-LIKE IMMUNOREACTIVITY IN THE BRAINS OF PUP-EXPOSED POSTPARTUM RATS

Fos-like immunoreactivity (fos-lir) was examined in sites within the ' 'maternal circuit'' in postpartum female rats that received various se nsory desensitizations and were exposed to pups for 1 or 2 hr. Neither olfactory bulbectomy nor thelectomy (nipple removal) significantly re duced the fos-lir in the anterior medial preoptic area (MPOA), althoug h reductions following bulbectomy in medial amygdala did occur. Periph erally induced hyposmia by ZnSo(4) reduced fos-iir in the olfactory st ructures (olfactory bulbs, piriform. cortex, and olfactory tubercle), in medial and cortical nuclei of the amygdala, but not in anterior MPO A. Application of the topical anesthetic Emla to the ventrum only redu ced fos-lir in the somatosensory cortex. Combined olfactory and ventra l desensitizations produced marginal reductions in posterior MPOA. It is suggested that the MPOA is primarily involved as part of the effect or system in the expression of the behavior. In contrast, the amygdala is involved in processing sensory cues received from pups during dam- litter interactions.