Using immunohistochemical techniques in combination with retrograde tracing, we have examined the innervating transmitters of several brainstem nuclei, including peptides, catecholamines and indoleamines. As a continuation of our interest in the hypothalamus, we have gathered evidence on an NPY-adrenaline projection from the brainstem to the paraventricular nucleus (PVN). Evidence has also been obtained that a subset of the corticotropin releasing factor (CRF) neurons in the PVN coexist with cholecystokinin (CCK). In addition, VIP projections in the hypothalamus have been examined with regard to projections from the suprachiasmatic nucleus to the median eminence. In another series of studies, we have confirmed a coexisting Substance P-serotonin projection to one area responsible for central respiratory control, the phrenic motor nucleus. In dorsal root ganglia, evidence has been obtained to suggest co-staining of a subpopulation of neurons with both carbonic anyhydrase and cholera toxin. Finally, ongoing studies are exploring: the coexistence of dynorphin and GABA; a complete mapping of the stria terminalis; and cholinergic projections to the mesencephalon.
