Influence of intrinsic nerves on electromyogram of cat colon in vitro

The electromyogram of the circular muscle layer of the cat colon was studied in vitro in superfused strips of muscle. Records exhibited electrical slow waves and migrating spike bursts, as described previously. Both the neurotoxin, tetrodotoxin, and the local anesthetic lidocaine, (P less than 0.05) prolonged the duration of migrating spike bursts, but migrating spike bursts were not affected by the adrenergic alpha-antagonist, phenoxybenzamine, nor by the adrenergic beta-antagonist, propranolol. Also, physostigmine and atropine did not affect them. Large concentrations of catecholamines did abolish them. This suggests that the migrating spike burst represents periodic release of the muscle from the tonic influence of nonadrenergic inhibitory nerves in the intramural plexuses. Slow-wave frequency and the congruence of slow waves were not affected (P greater than 0.05) by the antagonists listed above, nor by cholinergic and adrenergic agonists. This suggests that the slow waves are not importantly controlled by intrinsic nerves.