Expression of tyrosine hydroxylase within distinct populations of presympathetic‐pretomotor neurons in the rat brainstem

Numerous motivated behaviors require simultaneous activation of somatomotor and autonomic functions. We have previously characterized the organization of central circuits that likely mediate this integration. Using recombinant strains of pseudorabies virus (PRV) that express unique reporter proteins, we delineated the distribution of presympathetic‐pretomotor neurons (PSPMNs), which send descending poly‐synaptic projections with collaterals to skeletal muscle and the adrenal gland. A significant portion of these neurons was found within brain regions known to contain catecholaminergic neurons. Thus, we hypothesized that some of the PSPMNs utilize catecholamines as neurotransmitters. To test this hypothesis, we used fluorescent immunohistochemical approach to identify co‐localizations between PSPMNs and tyrosine hydroxylase (TH). Our findings indicate that while TH‐positive PSPMNs are present throughout the brainstem, most of them are found within: the locus coeruleus (LC), subcoeruleus area (SubC), A5, and A7 cell groups. Particularly, many of these neurons are clustered within a region that spans ventral LC, dorsal SubC, and the A7 cell group. These findings indicate that specific catecholaminergic cell groups participate in motor‐autonomic integration.