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 square wave pulses at 60 Hz, 1 ms duration and 300-509 mu A. 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. (C) 1999 Elsevier Science B.V. All rights reserved.