[Effect of verapamil on cerebral circulation]

Area of Science:

• Neuroscience
• Pharmacology
• Cardiovascular Physiology

Background:

• Cerebral vascular tone regulation is crucial for brain function.
• Verapamil is a calcium channel blocker with known cardiovascular effects.

Purpose of the Study:

• To investigate the effects of verapamil on cerebral circulation and vascular tone in anesthetized cats.
• To elucidate the mechanism of verapamil-induced vasodilation in the cerebral vasculature.

Main Methods:

• Acute experiments on anesthetized cats.
• Intravenous administration of verapamil at varying doses (0.05-1 mg/kg).
• Measurement of general arterial pressure, cerebral vascular tone, and cerebral circulation (volume velocity).
• Assessment of pial artery diameter and regional blood flow (cerebral cortex vs. reticular formation).
• Pharmacological blockade of various receptor types (beta-adrenoceptors, M-cholinoreceptors, histamine receptors) and sympatholytic agents were used to probe the mechanism.

Main Results:

• Verapamil dose-dependently reduced general arterial pressure and cerebral vascular tone.
• Cerebral circulation exhibited phasic changes influenced by vascular tone and arterial pressure.
• Increased blood flow was more pronounced in the cerebral cortex than the reticular formation.
• Partial pressure of oxygen (PO2) in the cerebral cortex correlated with local circulation.
• Pial artery diameter increased with both systemic and local verapamil administration.
• The vasodilatory effect of verapamil was not abolished by blocking beta-adrenoceptors, M-cholinoreceptors, histamine receptors, or by sympatholytic agents.

Conclusions:

• Verapamil induces vasodilation in the cerebral vasculature.
• The vasodilatory action of verapamil appears to be myotropic, possibly related to electrolyte metabolism.
• These findings contribute to understanding the cerebrovascular effects of verapamil and its potential therapeutic applications.