Synaptic transmission from splanchnic nerves to the adrenal medulla of guinea-pigs.

1. Membrane potentials were recorded with conventional intracellular microelectrodes from chromaffin cells in isolated, bisected adrenal glands from guinea-pigs. 2. All cells were electrically excitable and responded to depolarizing current with all-or-nothing action potentials that were blocked by tetrodotoxin. 3. Input resistance was 180 +/- 14 M omega and this was lower than that reported for isolated chromaffin cells using patch electrodes. 4. All cells responded to transmural stimulation with action potentials that arose from excitatory synaptic potentials in response to the excitation of one or more preganglionic fibres, many having strong synaptic action. Other fibres had weaker synaptic action but in all cases, maximal transmural stimulation caused depolarization well above threshold for action potential initiation. 5. Spontaneous excitatory synaptic potentials were observed whose frequency was greatly increased by repetitive stimulation at 10 or 30 Hz. 6. No evidence was found for the desensitization of nicotinic receptors in response to acetylcholine released from presynaptic nerve terminals. 7. These experiments show that there are many similarities between the responses to splanchnic nerve stimulation of guinea-pig chromaffin cells in situ and sympathetic ganglion cells from the same species.