The distribution of gamma-adrenoceptors and P2 purinoceptors in mesenteric arteries and veins of the guinea-pig.
1. Membrane potential changes and contractions were recorded from mesenteric arteries and veins of the guinea-pig, during perivascular nerve stimulation or application of noradrenaline or adenosine triphosphate (ATP). 2. After alpha-adrenoceptor blockade, noradrenaline activated low affinity adrenoceptors (gamma-adrenoceptors) causing depolarization and arterial contraction only in the presence of an inhibitor of catecholamine uptake. 3. Noradrenaline did not cause depolarization or contraction of the vein after alpha-adrenoceptor blockade even after catecholamine uptake was blocked. 4. Adenosine triphosphate caused depolarization and contraction of both arteries and veins. These responses were abolished by alpha-,beta-,methylene adenosine triphosphate (Me-ATP). 5. Me-ATP abolished rapid excitatory junction potentials (e.j.ps) caused by perivascular nerve stimulation of arteries but had no effect on arterial responses mediated by gamma-adrenoceptors. 6. In veins, perivascular nerve stimulation evoked slow e.j.ps which persisted in the presence of Me-ATP but were abolished after blockade of alpha-adrenoceptors. 7. The observations indicate that P2 purinoceptors are present on both mesenteric artery and vein whilst gamma-adrenoceptors are localized near the neuromuscular junction of the artery. However gamma-adrenoceptors do not appear to be directly involved in the generation of arterial e.j.ps.
Hirst
G D
GD
Department of Zoology, University of Melbourne, Parkville, Victoria, Australia.
Jobling
P
P
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D004594:Electrophysiology; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008638:Mesenteric Arteries / Q000187:drug effects / Q000502:physiology; D008642:Mesenteric Veins / Q000187:drug effects / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000187:drug effects / Q000502:physiology*; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology
D011941:Receptors, Adrenergic; D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; D009638:Norepinephrine