Evidence for adrenergic modulation of ganglionic transmission in the ganglia of the nerve of Remak of the chicken.

Adrenergic depression of ganglionic transmission in non-cholinergic, non-adrenergic (NCNA) excitatory nerves was investigated in the isolated chicken rectum with its associated nerve of Remak. Preganglionic stimulation of the NCNA nerves produced contraction of the rectum, an excitatory junction potential and discharges in the postganglionic axons. Preceding stimulation of descending fibers in the nerve of Remak suppressed these responses. These inhibitory effects were almost eliminated in reserpinized preparations, and were significantly reduced by pretreatment with guanethidine and phentolamine, but not with propranolol. Exogenously-applied adrenaline and noradrenaline mimicked the inhibitory effect of nerve stimulation on the discharge in the postganglionic axons. These results indicated that the nerve of Remak contained descending adrenergic fibers, stimulation of which caused suppression of ganglionic transmission in the NCNA excitatory pathways to the rectum, by the activation of alpha-adrenoceptors on the pre- or postganglionic NCNA neuron.