Antagonism by propranolol of the ganglion stimulant action of 5-hydroxytryptamine.
Eur J Pharmacol, 1975/6-1975/7;32(02):293-301.
PMID: 238859
Impact factor: 5.195
Abstract
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.
MeSH terms
Acetylcholine; Adrenergic beta-Antagonists; Animals; Cats; Dimethylphenylpiperazinium Iodide; Electric Stimulation; Ganglia, Spinal; Ganglionic Stimulants; In Vitro Techniques; Muscle Contraction; Nictitating Membrane; Norepinephrine; Propranolol; Serotonin Antagonists; Stimulation, Chemical
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