Antagonism by propranolol of the ganglion stimulant action of 5-hydroxytryptamine.
The effects of racemic propranolol and its constituent isomers were studied on ganglionic stimulation produced in situ by close arterial injection of 5-HT and DMPP to the superior cervical ganglion. Ganglion stimulation was recorded in terms of the resultant contraction of the nictitating membrane. d,l-Propranolol caused a biphasic antagonism of the ganglion stimulant effect of 5-HT. At low doses, 0.5-10 mug, the antagonism was surmountable by increasing the amount of 5-HT. The l-isomer (0.2-4 mug) but not d-propranolol also caused antagonism. At higher doses, 0.1-5 mg, both d,l- and d-propranolol caused a second type of blockade of 5-HT which was not surmountable and resembled that seen with procaine. The ganglion stimulant effects of DMPP and acetylcholine were only antagonised by the higher doses of d- and d,l-propranolol. d,l-Propranolol did not reduce the direct stimulation by 5-HT on the muscle of the nictitating membrane.
D000109:Acetylcholine / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D002415:Cats; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004558:Electric Stimulation; D005727:Ganglia, Spinal / Q000187:drug effects*; D005731:Ganglionic Stimulants / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009541:Nictitating Membrane / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology*; D012702:Serotonin Antagonists; D013268:Stimulation, Chemical
D000319:Adrenergic beta-Antagonists; D005731:Ganglionic Stimulants; D012702:Serotonin Antagonists; D004246:Dimethylphenylpiperazinium Iodide; D011433:Propranolol; D000109:Acetylcholine; D009638:Norepinephrine