The rabbit mesenteric vein: a specific bioassay for substance P.

Area of Science:

• Pharmacology
• Vascular Biology
• Neuroscience

Background:

• The anterior mesenteric vein of the rabbit exhibits high sensitivity to various vasoactive agents.
• Substance P is a potent peptide that elicits contractions in vascular smooth muscle.

Purpose of the Study:

• To investigate the mechanism of action of substance P on the rabbit mesenteric vein.
• To determine if the rabbit mesenteric vein can be made selective for substance P using specific inhibitors.
• To explore the interaction between substance P and other vasoactive peptides like bradykinin.

Main Methods:

• Dose-response studies of substance P on rabbit mesenteric vein.
• Use of specific inhibitors to block the effects of acetylcholine, catecholamines, histamine, 5-hydroxytryptamine, angiotensin, and bradykinin.
• Assessment of substance P activity on tissues pretreated with indomethacin.

Main Results:

• Substance P induced dose-dependent contractions in the rabbit mesenteric vein.
• Specific inhibitors rendered the vein selective for substance P by blocking other agents without affecting substance P-induced contractions.
• Substance P appears to act directly on specific receptors, independent of neurotransmitter release or intramural prostaglandins.
• The rabbit mesenteric vein possesses a novel bradykinin receptor, distinguishable from substance P receptors.

Conclusions:

• The rabbit mesenteric vein is a valuable model for studying substance P's direct vascular effects.
• Pharmacological manipulation can achieve selectivity for substance P in vascular smooth muscle.
• The identification of distinct receptors for substance P and bradykinin in the mesenteric vein offers insights into peptide-receptor interactions.