Central monoamine systems and new antihypertensive agents

Area of Science:

• Pharmacology
• Neuroscience
• Cardiovascular Research

Background:

• Centrally acting antihypertensive agents modulate blood pressure via the central nervous system.
• First-generation agents (clonidine, alpha-methyldopa) target alpha-2 adrenoceptors, while newer agents (rilmenidine, moxonidine) target imidazoline receptors.

Purpose of the Study:

• To elucidate the relationship between central monoamine pathways and the mechanism of action of centrally acting antihypertensive agents.
• To compare the receptor targets and pathway dependencies of first- and second-generation antihypertensive drugs.

Main Methods:

• Review of studies utilizing receptor antagonists and chemical lesioning techniques.
• Investigation of the effects of clonidine, alpha-methyldopa, rilmenidine, and moxonidine on blood pressure.
• Assessment of the role of noradrenergic and serotonergic pathways in the brainstem.

Main Results:

• Both alpha-2 adrenoceptor and imidazoline receptor agonists produced hypotension dependent on central monoamine pathways.
• Lesioning of brainstem noradrenergic or serotonergic pathways attenuated the hypotensive effects of these agents.
• Evidence suggests these drugs mimic noradrenergic function and inhibit pressor serotonergic pathways.

Conclusions:

• Centrally acting antihypertensive agents, despite differing receptor targets, share a common dependence on brainstem monoamine pathways.
• The findings suggest alpha-2 adrenoceptors and imidazoline receptors function in series within these pathways to regulate blood pressure.