Localization of Catecholaminergic Receptor Sites in the Nucleus Tractus Solitarii involved in the Regulation of Arterial Blood Pressure

It was found that the minimum effective dose of α-methylnoradrenaline in NTS region causing a hypotensive response after bilateral local application was 80 pmoles, and data suggest that the area of the NTS may be a site of action for central hypotensive drugs that act by adrenergic receptor stimulation in the brain.

Abstract

This chapter discusses the localization of catecholaminergic receptor sites in the nucleus tractus solitarii (NTS) involved in the regulation of arterial blood pressure. Studies indicate that the NTS of the medulla oblongata—a primary site of termination of afferent carotid sinus baroreceptor fibers—plays an important role. For example, ablation of the area of the NTS produces acute hypertension in conscious rats, and electrical stimulation of the mediocaudal part of the NTS causes hypotension and bradycsudia. This area has been shown by fluorescent histochemistry to be heavily innervated by catecholaminergic terminals; it also contains catecholaminergic cell bodies. Bilateral local application of noradrenaline and α-methylnoradrenaline (MNA) in this area cause hypotension. In addition, prior administration at the same site of the α-adrenergic blocking agent—phentolamine—prevents the central inhibitory action of the two catecholamines and may even reverse the effect on blood pressure. These data suggest that the area of the NTS may be a site of action for central hypotensive drugs that act by adrenergic receptor stimulation in the brain. In experiment, it was found that the minimum effective dose of α-methylnoradrenaline in NTS region causing a hypotensive response after bilateral local application was 80 pmoles. In contrast, an injection of physostigmine in the same region elicited a hypertensive response.