Effects of nucleus basalis magnocellularis stimulation on a socially transmitted food preference and c-Fos expression

Experiment 1 examined the effects of electrical stimulation of nucleus basalis magnocellularis (NBM) on a relational odor-association task--the social transmission of food preference (STFP). Rats were stimulated unilaterally in the NBM for 20 min (100 microA, 1 Hz) immediately before the social training. They were tested on their ability to remember preference for the trained food either immediately or following a 24-h delay. Stimulation of NBM improved retention regardless of delay, and additional behavioral measures (social interaction, motor activity, or exploration) did not account for such effects. Experiment 2 investigated brain regions activated after NBM electrical stimulation by examining the induction of c-Fos. This treatment led to bilateral increased c-Fos expression in prefrontal regions, such as orbitofrontal, prelimbic, and infralimbic cortices, and some hippocampal subregions (dorsal CA and ventral dentate gyrus). In contrast, no differences between groups in c-Fos expression were found in basolateral amygdala, dorsal dentate gyrus, ventral CA, or ventral subiculum. Present findings indicate that pretraining NBM electrical stimulation facilitates the acquisition of STFP, supporting a role of NBM in the early stages of memory formation, and suggest that the treatment might cause such effects by inducing neural changes, related to transcription factors such as c-Fos, in the prefrontal cortex or the hippocampal formation.