Sympathetic modulation of cholinergic transmission in cat vesical ganglia is mediated by alpha 1- and alpha 2-adrenoceptors.
Modulation of transmission in cat vesical ganglia by exogenous catecholamines or short periods of hypogastric nerve stimulation (HGS) was examined in vivo. HGS (30 Hz, 30 V, 10- to 20-s train) initially caused inhibition of ganglionic transmission, followed by a period of facilitation. The inhibition could be evoked by lower stimulus intensities than the facilitation. The biphasic effect was mimicked by norepinephrine (2-10 micrograms) injected into the inferior mesenteric artery, whereas phenylephrine (5-10 micrograms) usually caused only facilitation. The administration of specific adrenoceptor antagonists showed that the inhibitory responses were mediated by alpha 2-receptors and the facilitatory responses by alpha 1-receptors. The effects of HGS and norepinephrine were also tested on pelvic nerve-evoked bladder contractions. Both caused a brief reduction in contraction amplitude which, for the HGS effect, was mediated mainly by alpha 2-receptors. Noradrenergic inhibition of bladder contractions was mediated by both alpha 2- and beta-adrenoceptors. These studies have shown that sympathetic modulation of ganglionic transmission in the bladder can be either inhibitory or facilitatory, each mediated by a specific receptor type. These two actions may be important during different stages of bladder storage or voiding.
Keast
J R
JR
Department of Pharmacology, School of Medicine, University of Pittsburgh, Pennsylvania 15261.
Kawatani
M
M
De Groat
W C
WC
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D002415:Cats; D004558:Electric Stimulation; D005260:Female; D005724:Ganglia / Q000502:physiology*; D007001:Hypogastric Plexus / Q000187:drug effects / Q000502:physiology; D008297:Male; D009119:Muscle Contraction; D009638:Norepinephrine / Q000494:pharmacology; D010275:Parasympathetic Nervous System / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D001743:Urinary Bladder / Q000294:innervation* / Q000502:physiology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; D009638:Norepinephrine