Effect of iontophoretic application of cholinergic agonists and their antagonists to guinea‐pig pelvic ganglia

The electrical activity of guinea‐pig pelvic ganglion cells following iontophoretically applied cholinergic drugs, alone and during orthodromic nerve stimulation via the hypogastric nerve, has been recorded intracellularly. Iontophoretic application of nicotine (Nic) and acetylcholine (ACh) reduced membrane resistance and caused a depolarization which in approximately 80% of cells led to the firing of action potentials. In the remainder, depolarization was unaccompanied by firing. Iontophoretic application of Nic and ACh reduced or abolished the amplitude of successively evoked orthodromic responses. ACh‐induced depolarization, unlike that caused by tetanic stimulation, was not followed by a subsequent increase in the frequency of synaptic potentials. Di‐hydroβerythroidine (DHβE) and atropine (Atr) inhibited the response to both orthodromic stimulation and iontophoretic application of Nic and ACh. There was no evidence for the existence of muscarinic receptors in guinea‐pig pelvic ganglia. Iontophoretic application of muscarinic agonists alone and after tetanic stimulation of the hypogastric nerve produced no significant depolarization of the ganglion cell membrane. 1971 British Pharmacological Society