Effects of selective applications of drugs affecting ganglionic transmission to the hypogastric ganglion of the guinea pig

Abstract

Effects of selective applications of drugs to the guinea pig hypogastric ganglion were studied on the contractile response of the vas deferens to the hypogastric nerve stimulation or to ganglionic stimulating drugs. Both acetylcholine (ACh) and dimethylphenylpiperazinium (DMPP) contracted the vas deferens. Neostigmine potentiated the ACh-induced contractions but not those which were DMPP-induced. Hemicholinium-3 (HC-3) reduced the response to nerve stimulation (R-NS) but affected neither the ACh-induced contractions nor the DMPP-induced contractions. Morphine blocked R-NS but not the ACh-induced and the DMPPinduced contractions. Hexamethonium reduced R-NS and the contractions to ACh or to DMPP. Methacholine and bethanechol applied before and after preganglionic tetanic stimulation of the hypogastric nerve produced no change of tone of the vas deferens. Atropine did not antagonize the responses which were produced by nerve stimulation, ACh or DMPP. These results support the classic hypothesis that ganglionic transmission is mediated by nicotinic receptors but do not provide evidence that muscarinic receptors exist at the synapses of this preparation.