The long lasting effects of electrical simulation of the medial preoptic area and medial amygdala on maternal behavior in female rats

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 s quare wave pulses at 60 Hz, 1 ms duration and 300-509 mu A. Confirmation of afterdischarge using these parametres was established. In the first experi ment, maternally experienced (but not post-partum) MedAmyg stimulated anima ls became maternal more slowly than did MedAmyg not stimulated animals or t han 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 st imulation had no effect on CPP performance, but produced a decreased prefer ence 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 in volved in facilitating and attenuating maternal responsiveness and related (precursor?) behaviors, respectively. It appears that chronic (kindling-lik e) stimulation of these neural substrates enhances their functions. (C) 199 9 Elsevier Science B.V. All rights reserved.