Acetylcholine receptor agonists stimulate [3H]taurine release from rat sympathetic ganglia

The endogenous taurine content, and the uptake and release of [3H]taurine were examined using the rat superior cervical ganglion. Taurine was found to be one of the most abundant amino acids in the superior cervical ganglion, and the superior cervical ganglion took up [3H]taurine from the incubation medium. Carbachol stimulated the release of [3H]taurine in a concentration-dependent manner with an EC50 of 26 microM and maximal stimulation at 100 microM. The nicotinic receptor agonist 1,1-dimethyl-4-phenylpiperazinium stimulated release with the same potency but with greater efficacy than carbachol. The nicotinic receptor antagonist hexamethonium (1 mM) inhibited carbachol-stimulated release by 74%. (+/-)-Muscarine stimulated release with an EC50 of 8 microM but with a maximal effect of only 32% of that produced by 100 microM carbachol. Oxotremorine, another muscarinic receptor agonist, was ineffective, even at 1 mM. The muscarinic receptor antagonist atropine inhibited carbachol-stimulated release by 30% at 10 microM. These results show that [3H]taurine release from rat superior cervical ganglion can be stimulated by cholinergic receptor agonists. Release is mediated predominantly by a nicotinic receptor and partially by a muscarinic receptor.