Stimulation of the subcallosal fornix excites neurones in the cat preoptic region which project to the medial basal hypothalamus and in the medial forebrain bundle

Abstract

The projection of neurones in the cat preoptic region driven by stimulation of the subcallosal fornix was systematically explored. We found 19% projected to the medial basal hypothalamus (MBH) and 10% projected in the medial forebrain bundle (MFB). Neurones projecting to 3he MBH were driven more often by stimulation of the lateral aspect of the fornix than the medial aspect ( P = 0.006) and these neurones were thought to lie in the medial division of the preoptic nucleus (MPNm) since they were found significantly more often in the medial 0.6 mm of the preoptic region than more laterally ( P = 0.028). A reverse projection from the preoptic region in the fornix is also suggested based on the finding of 24 antidromically activated neurones inthe preoptic region following stimulation of the fornix.