Extra-hypothalamic vasopressin neurons coexpress galanin messenger RNA as shown by double in situ hybridization...

Vasopressin (VP) neurons in the bed nucleus of the stria terminalis (BNST) and medial amygdala (AMe) exhibit sexual dimorphism and steroid dependency. VP neurons in the supraoptic nucleus and paraventricular nucleus have been shown to coexpress other transmitters including galanin (GAL). However, little is known about what other neurotransmitters may be colocalized with VP in the BNST and AMe. Here, we have used radio-labeled and digoxigenin-labeled cRNA probes to perform double in situ hybridization histochemistry for VP and GAL in the BNST and AMe of intact, adult male rats. We provide evidence that in the basal state, the majority of VP-synthesizing cells in the BNST and AMe of the adult male rat also express galanin mRNA. Likewise, the majority of GAL-expressing neurons in these regions also contain VP mRNA. These findings give further evidence for the similarity of the BNST and AMe and provide a rationale for studies investigating the role of GAL in functions involving extrahypothalamic VP pathways.