dinoprost and alpha-beta-methyleneadenosine-5--triphosphate

We investigated whether M(2) muscarinic receptor activation opposes isoproterenol-induced relaxation in mouse urinary bladder and whether endogenous acetylcholine acts through a similar M(2) mechanism. When measured in urinary bladder from M(3) receptor knockout mice, the muscarinic agonist oxotremorine-M elicited only very weak contractions. In the presence of alpha,beta-methylene ATP (30 microM) and isoproterenol (1 microM), however, oxotremorine-M elicited a robust contractile response. This response was completely absent in bladder from M(2)/M(3) double knockout mice, indicating that activation of the M(2) receptor inhibits the relaxant effect of isoproterenol on the contraction to alpha,beta-methylene ATP. Similar results were obtained when prostaglandin F(2alpha) (5 microM) was used as the contractile agent but not when serotonin was used. Electrical field stimulation of the urinary bladder from wild-type mouse elicited contractions that were inhibited 20% by atropine and 40% by desensitization with alpha,beta-methylene ATP. When measured in the presence of alpha,beta-methylene ATP to desensitize the purinergic component of contraction, isoproterenol exhibited moderately greater relaxant activity in field-stimulated bladder from the M(2) knockout mouse compared with that observed in wild-type bladder. This differential relaxant effect of isoproterenol was greatly increased in the presence of physostigmine. In contrast, no differential effects were noted for isoproterenol in similar experiments on bladders from M(3) knockout and M(2)/M(3) double knockout mice in the presence of physostigmine. Our results suggest that neuronally released acetylcholine acts on the M(2) muscarinic receptor to inhibit the relaxant effect of isoproterenol on the minor, cholinergic component of contraction in the field-stimulated mouse urinary bladder.

Topics: Acetylcholine; Adenosine Triphosphate; Animals; Atropine; Cholinergic Fibers; Dinoprost; Electric Stimulation; Female; Isoproterenol; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscarinic Agonists; Muscle Contraction; Oxotremorine; Physostigmine; Potassium Chloride; Receptor, Muscarinic M2; Receptor, Muscarinic M3; Serotonin; Tetrodotoxin; Urinary Bladder

In isolated canine lingual arteries denuded of the endothelium, transmural electrical stimulation (2-20 Hz) produced a frequency-related contraction which was not significantly influenced by prazosin but which was reversed to a relaxation by alpha,beta-methylene ATP. The responses were abolished by tetrodotoxin. The stimulation-induced relaxation was abolished by treatment with NG-nitro-L-arginine (L-NA, 10(-6) M) and restored by the addition of L-arginine. Neurogenic relaxation resistant to L-NA was not observed after electrical stimulation, even though the pulse width and stimulus intensity were raised. Under treatment with prazosin, alpha,beta-methylene ATP and indomethacin, the arterial strips responded to nicotine (10(-4) M) with a marked relaxation that was abolished by hexamethonium. The relaxation was significantly inhibited but not abolished by L-NA (10(-5) M), and raising the concentration of the inhibitor to 10(-4) M, did not produce additional inhibition. In the strips treated with L-NA, the nicotine-induced relaxation was abolished or markedly reduced under desensitization with vasoactive intestinal peptide (VIP) or calcitonin gene-related peptide (CGRP) and by treatment with high concentrations of beraprost, a stable analog of prostaglandin I2, but was unaffected by CGRP or VIP receptor antagonists. Relaxant responses to a low concentration of nicotine (5 x 10(-6) M) were abolished by L-NA and restored by L-arginine. Histochemical study demonstrated many nerve fibers and bundles containing NADPH diaphorase in the adventitia of the arteries. It is concluded that the neurogenic arterial contraction is induced mainly by ATP via stimulation of P2X purinoceptors, and that the relaxation induced by electrical stimulation or a low concentration of nicotine is mediated by nitric oxide (NO) released from perivascular nerves. In high concentrations, nicotine elicits marked relaxations possibly due to the liberation of NO from the nerve and also vasodilator substances that increase the content of cyclic AMP in the tissue. CGRP and VIP are unlikely to be involved.

Topics: Adenosine Triphosphate; Adrenergic alpha-Antagonists; Animals; Arteries; Dinoprost; Dogs; Electric Stimulation; Female; Ganglionic Stimulants; In Vitro Techniques; Male; Nicotine; Prazosin; Tongue; Vasoconstriction; Vasodilation

In isolated monkey lingual arteries denuded of the endothelium and contracted with prostaglandin F2alpha, transmural electrical stimulation produced a contraction that was reduced by prazosin and reversed to a relaxation by additional treatment with alpha,beta-methylene ATP. The relaxation thus induced was abolished by tetrodotoxin and N(G)-nitro-L-arginine (L-NNA), a nitric oxide (NO) synthase inhibitor, and L- but not D-arginine restored the response in the L-NNA-treated arteries. Under treatment with prazosin and alpha,beta-methylene ATP, the arterial strips responded to nicotine with a relaxation that was not influenced by atropine and timolol but was abolished by hexamethonium, oxyhemoglobin, and methylene blue. The nicotine-induced relaxation was abolished by L-NNA but not by N(G)-nitro-D-arginine and was reversed by L-arginine. Relaxations to exogenously applied NO (acidified NaNO2 solution) were not influenced by L-NNA but were abolished by oxyhemoglobin and methylene blue. The response was not affected in the strips made unresponsive to vasoactive intestinal polypeptide and calcitonin gene-related peptide by desensitization. Histochemical study demonstrated the presence of perivascular neurons containing neuronal NO synthase. It is concluded that monkey lingual arteries are innervated by vasoconstrictor nerves liberating norepinephrine and possibly ATP and also by nonadrenergic noncholinergic vasodilator nerves liberating NO as a neurotransmitter to activate soluble guanylate cyclase. Vasoactive intestinal polypeptide and calcitonin gene-related peptide do not appear to be involved in the neurogenic vasodilatation.

Topics: Adenosine Triphosphate; Animals; Arteries; Dinoprost; Electric Stimulation; Female; In Vitro Techniques; Macaca; Male; Muscle, Smooth, Vascular; Nerve Fibers; Neurons; Nicotine; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Prazosin; Stereoisomerism; Tongue; Vasodilation

In the presence of prazosin and propranolol, electrical transmural stimulation of isolated dog mesenteric artery produced a sympathetic purinergic contraction, which was followed by a relaxation in PGF2 alpha-contracted arteries. Such purinergic responses were mimicked by brief exposure to alpha, beta-methylene ATP (alpha, beta-Me ATP) and were completely inhibited after desensitization of P2x-purinergic receptors. However, exogenous ATP predominantly evoked a relaxation in PGF2 alpha-contracted artery. These results suggest that the sympathetic purinergic response may be caused by a P2x-purinergic receptor-selective mechanism or substance, rather than ATP.

Topics: Adenosine Triphosphate; Animals; Dinoprost; Dogs; Electric Stimulation; Female; In Vitro Techniques; Male; Mesenteric Arteries; Prazosin; Propranolol; Receptors, Purinergic; Sympathetic Nervous System