Participation of nucleus reticularis gigantocellularis in guanabenz-promoted hypotension, decrease in cardiac...

Area of Science:

• Neuroscience
• Cardiovascular Pharmacology
• Physiology

Background:

• Guanabenz is an antihypertensive agent.
• Its central nervous system mechanisms are not fully understood.
• The nucleus reticularis gigantocellularis is implicated in cardiovascular regulation.

Purpose of the Study:

• To investigate the role of the nucleus reticularis gigantocellularis in the cardiovascular effects of guanabenz.
• To determine if guanabenz acts centrally to induce hypotension, reduced cardiac contractility, and bradycardia.

Main Methods:

• Experiments were conducted on pentobarbital-anesthetized rats.
• Systemic administration of guanabenz.
• Bilateral electrolytic lesions of the nucleus reticularis gigantocellularis.
• Microinjections of guanabenz into specific regions of the nucleus reticularis gigantocellularis.

Main Results:

• Systemic guanabenz induced transient hypertension followed by sustained hypotension, decreased cardiac contractility, and bradycardia.
• Lesions of the nucleus reticularis gigantocellularis abolished the depressant cardiovascular effects of guanabenz.
• Microinjection into the ventro-medial nucleus reticularis gigantocellularis mimicked systemic effects, while lateral application had minimal impact.

Conclusions:

• The nucleus reticularis gigantocellularis is a key central site mediating the cardiovascular suppressant effects of guanabenz.
• Guanabenz's hypotensive, cardiac depressant, and bradycardic actions are, at least in part, centrally mediated via this nucleus.