Localization of neuropeptide Y Y-1 receptor-like immunoreactivity in catecholaminergic neurons of the rat medulla oblongata

Neuropeptide Y receptors in the medulla oblongata participate in central cardiovascular control. The neuropeptide Y-1 receptor subtype gene and amino acid sequence have been identified by molecular cloning studies. In this study, a C-terminal peptide representing amino acids 355-382 of the neuropeptide Y-1 receptor was synthesized and cross-linked to thyroglobulin to produce an antibody against a partial sequence of the neuropeptide Y-1 receptor, used to localize neuropeptide Y-1 receptor-like immunoreactivity in the catecholaminergic neurons of the medulla oblongata. The double colour immunofluorescence technique with a polyclonal antibody against the neuropeptide Y-1 receptor and a monoclonal antibody against tyrosine hydroxylase revealed that in the rat medulla oblongata, a weak (the C3 cell group) to moderately intense (the A1, A2, C1 and C2 cell groups), diffuse cytoplasmic neuropeptide Y-1 receptor-like immunoreactivity was distributed primarily in the noradrenergic and adrenergic cell bodies and occasionally seen in the noradrenergic and adrenergic cell processes. Almost all tyrosine hydroxylase-like immunoreactive cell bodies in the A1, A2, C1, C2 and C3 cell groups showed neuropeptide Y-1 receptor-like immunoreactivity. The neuropeptide Y-1 receptor-like immunoreactivity in the A2 cell group was somewhat stronger. The present findings show localization of specific neuropeptide Y-1 receptor-like immunoreactivity in the vast majority of the noradrenergic and adrenergic cell bodies of the A1, A2, C1, C2 and C3 cell groups, which are putative cardiovascular regions. The results support the view that neuropeptide Y-1 receptors in the medulla oblongata are involved in central cardiovascular control and may coexist with another important receptor, the alpha(2A)-adrenoceptor, also involved in central cardiovascular regulation, since the alpha(2A)-adrenoceptor-like immunoreactivity has been shown to exist in almost all noradrenergic and adrenergic cell bodies in the brainstem. In conclusion, centrally administered neuropeptide Y may act in part via neuropeptide Y-1 receptors located on the soma and dendrites of noradrenergic and adrenergic neurons, where it may interact with alpha(2)-adrenoceptors at least in the noradrenergic A2 neurons. This noradrenaline system may be involved in at least part of the vasodepressor actions of neuropeptide Y-1 noradrenaline and adrenaline in the nucleus tractus solitarii in view of the present findings. Copyright (C) 1996 IBRO.