Evidence for a catecholamine-mediated slow hyperpolarizing synaptic response in parasympathetic ganglia.

Stimulation of preganglionic nerve trunks in the presence of muscarinic and nicotinic cholinoceptor and purinoceptor antagonists produced a slow-hyperpolarizing synaptic potential that was mimicked by exogenously applied norepinephrine. Both responses were blocked by yohimbine, an alpha-adrenoceptor antagonist, and enhanced by imipramine and cocaine, inhibitors of norepinephrine reuptake. These findings fulfill pharmacological criteria suggesting that norepinephrine is a neurotransmitter in cat bladder parasympathetic ganglia.