A gradient of synaptic efficacy and its presynaptic basis in the cercal system of the cockroach.

1. The cerci of the cockroach Periplaneta americana bear longitudinal columns of wind-sensitive receptors which provide excitatory inputs to the giant interneurons (GIs) of the abdominal nerve cord. By using sound stimuli, we showed that spikes were more easily induced in the GIs from the most proximal than from the most distal receptors of the same column.

[Effect of difluorodichloromethane (FC 12) on the cardiac cellular electric activity of mammals].

The cardiotoxicity of high concentrations of inhaled difluorodichloromethane (FC 12) has now been acknowledged. In the present study, the effects of FC 12 on the electrical activity of cells in the atrial and ventricular myocardium of anesthetized rats were recorded with "flexibly mounted" intracellular microelectrodes. The major phenomena observed in both types of cells were: a distinct decrease in the diastolic potential, a decrease inthe amplitude of the action potential, modifications in the shape of the action potential.

Postsynaptic effects of 4-aminopyridine in the sixth abdominal ganglion of the cockroach.

The synaptic action of 4-aminopyridine (4-AP) was studied in the sixth abdominal ganglion of the cockroach Periplaneta americana L. The drug 4-AP did not modify the affinity of cholinergic receptors. At concentrations above 10(-4)M, 4-AP depolarized the postsynaptic membranes even after blockage of muscarinic and nicotinic receptors by antagonistic substances.

Synaptic transmission in the sixth ganglion of the cockroach: action of 4-aminopyridine.

1. Study was made of the action of 4-aminopyridine (5 X 10(-5) M) on synaptic transmission in the last abdominal ganglion of Periplaneta americana. The 'oil-gap' technique was used to record postsynaptic events in a single giant axon.

The pharmacology of an insect ganglion: actions of carbamylcholine and acetylcholine.

1. Methods for presenting dose-response data for the ganglionic actions of cholinergic agonists (e.g.