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A program of repeated electrical (kindling-like) stimulation of the medial preoptic area (MPOA) or the medial amygdala (MedAmyg) on maternal and other behaviors were investigated. Stimulation was applied daily for 14 days (or until a stage 3 motor seizure was observed) using 2 s trains of biphasic square wave pulses at 60 Hz, 1 ms duration and 300-500 microA. Confirmation of afterdischarge using these parametres was established. In the first experiment, maternally experienced (but not post-partum) MedAmyg stimulated animals became maternal more slowly than did MedAmyg not stimulated animals or than MPOA stimulated animals. In the second experiment, virgin animals were used. MPOA stimulation enhanced the female's preference for pup associated environments in the conditioned place preference (CPP) paradigm. MedAmyg stimulation had no effect on CPP performance, but produced a decreased preference for pup odors in a modified hole board test and increased 'anxiety' in the open field. These results confirm that the MPOA and the MedAmyg are involved in facilitating and attenuating maternal responsiveness and related (precursor?) behaviors, respectively. It appears that chronic (kindling-like) stimulation of these neural substrates enhances their functions.

The role of perioral and ventral-trunk somatosensory stimulation from pups mediating the initial expression of maternal behavior and its long-term retention 8 days later, was investigated. Six groups of female rats were permitted to physically interact with four 1-5-day-old foster pups for 1 h, 36 h after Cesarean delivery on gestation day 21. Prior to this maternal experience, dams were subjected to: reduced cutaneous rostral snout sensitivity (anaptia) by injection of lidocaine into the mystacial pads; reduced ventral-trunk sensations by occlusion of the entire ventrum with a full spandex jacket; both manipulations; or control manipulations. Additional groups of females not receiving a maternal experience (inexperienced) also received the somatosensory deprivation or control manipulations. During retention testing, rats in the singly manipulated experienced groups exhibited reduced latencies to become maternal in comparison to their inexperienced counterparts (approximately 3 days vs. 8 days). However, rats previously rendered both anaptic and ventrally-occluded responded like inexperienced rats in showing a long latency to become maternal (8 days). Thus, reduction of either perioral or ventral somatosensory contact from pups did not block the maternal experience effect, but reduction of both of these inputs did.