SYNAPTIC CONNECTIONS BETWEEN SUBSTANCE P-CONTAINING AXONS AND ESTROGEN RECEPTOR-SYNTHESIZING NEURONS IN THE MEDIAL PREOPTIC AREA OF THE RAT-BRAIN

Dual-label immunocytochemical procedures were employed to provide ultr astructural evidence for the presence of substance P (SP) in afferents to estrogen-receptive neurons in the medial preoptic area (MPO) of th e female rat. SP-immunoreactive axon terminals were observed to innerv ate the periventricular (PvPO) and medial (MPN) preoptic nuclei of the MPO densely, and to form synaptic connections at these sites with neu rons which contain estrogen receptors in their nucleus. These results indicate that estrogen-receptive preoptic neurons may be regulated by SP-containing neuronal pathways via synaptic mechanisms. (C) 1998 Else vier Science B.V.