Quantitative evaluation of alpha- and beta-adrenoceptor modulation of [3H]choline release in guinea pig superior cervical ganglia.
[3H] Overflow evoked by 5 min supramaximal preganglionic stimulation at 1 pps has been studied in isolated guinea pig superior cervical ganglion preparations preincubated with [3H]choline. At 15 microM norepinephrine (NE) reduced both the [3H]choline overflow and endogenous acetylcholine release by 59.4 and 54.1% respectively; the dose-response curve for NE inhibitory action is described. Evidence is given that endogenous catecholamines effectively reduce ACh release from the ganglia. After blocking the inhibitory action of endogenous NE, a significant beta-adrenoceptor-mediated facilitatory effect on ACh release could be observed. Preincubation of the ganglia with different combinations of alpha 1 and alpha 2 agonists (phenylephrine, 10 microM and clonidine, 1 microM respectively) and antagonists (prazosin, 10 microM and yohimbine, 3 microM) showed that the adrenoceptors involved in alpha-mediated NE inhibition of ACh output are exclusively of the alpha 2-type.
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D002794:Choline / Q000378:metabolism*; D003000:Clonidine / Q000494:pharmacology; D005728:Ganglia, Sympathetic / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D009638:Norepinephrine / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D015016:Yohimbine; D007545:Isoproterenol; D003000:Clonidine; D002794:Choline; D000109:Acetylcholine; D009638:Norepinephrine; D011224:Prazosin; D010646:Phentolamine