Does substance P coexist with adrenaline in neurones of the rostral ventrolateral medulla in the rat?

Spinally projecting substance P- (SP) and adrenaline-containing neurones of the rostral ventrolateral medulla are believed to be important in the tonic and reflex control of blood pressure. In this paper we used dual immunofluorescence staining to investigate the degree of co-localisation of these two putative neurotransmitters in this region. In contrast to a recent report that SP and phenylethanolamine-N-methyltransferase (PNMT) are extensively co-localised, we report here that only a small number of neurones were found to be immunoreactive for both SP and PNMT.