Electromechanical coupling in rat basilar artery in response to morphine

Area of Science:

• Pharmacology
• Vascular Physiology

Background:

• Morphine and meperidine are narcotics with effects on the cardiovascular system.
• The rat basilar artery is a model for studying cerebral vascular smooth muscle.

Purpose of the Study:

• To investigate the mechanism of action of morphine sulfate and meperidine hydrochloride on rat basilar artery.
• To determine the effects of these agents on vascular smooth muscle contractility and electrical properties.

Main Methods:

• Measurements of force development, intracellular membrane potential (Em), and voltage-current curves in rat basilar artery.
• Application of morphine sulfate, meperidine hydrochloride, and naloxone.
• Electrical studies involving current pulses to assess input resistance (rin) and membrane potential changes (delta V).

Main Results:

• Morphine sulfate induced a dose-dependent contraction, reversible by naloxone.
• Morphine sulfate depolarized vascular smooth muscle cells and increased input resistance, suggesting decreased potassium conductance (gk).
• Meperidine hydrochloride exhibited significantly less effect on the preparation compared to morphine sulfate.

Conclusions:

• Morphine sulfate likely acts on rat basilar artery smooth muscle by reducing potassium conductance.
• The findings provide insight into the vascular effects of morphine.
• Naloxone's vehicle demonstrated in vitro vasodilator properties on cerebral vascular smooth muscle.