EFFECTS OF HEXAMETHONIUM AND TETRAETHYLAMMONIUM ON CARDIAC ARRHYTHMIAS PRODUCED BY PENTYLENETETRAZOL, PICROTOXIN AND DESLAXOSIDE IN DOGS

¹ Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, N. Y.

Hexamethonium, 0.4 mg/kg i.v., prevents or converts cardiac (ventricular) arrhythmias induced by fourth ventricle injections of pentylenetetrazol (5 mg/kg), picrotoxin (5 µg/kg), or deslanoside ( 4 µg/kg), without affecting EEG convulsive discharges or markedly reducing the blood pressure or the heart rate. This is a further indication of central autonomic origin of these arrhythmias. A larger dose of hexamethonium, 0.8 to 12 mg/kg i.v., is required to prevent or convert arrhythmias induced by pentylenetetrazol, 30 mg/kg i.v., or picrotoxin, 2 mg/kg i.v. The difference in doses of hexamethonium for prevention and conversion of arrhythmias induced by the analeptics via the fourth ventricle and intravenous routes indicates that these latter agents may have some secondary peripheral sites of action on the autonomic ganglia or the heart. Hexamethonium has no effect on arrhythmias produced by deslanoside, 0.3 mg/kg i.v.

Hexamethonium, administered into the fourth ventricle in the doses of 0.04 to 0.12 mg/kg, is also effective in blocking arrhythmias induced by pentylenetetrazol or picrotoxin administered either intravenously or into the fourth ventricle, or by deslanoside into the fourth ventricle.

Tetraethylammonium, TEA, given i.v. or intraventricularly in 10 times the hexamethonium doses is equally effective against arrhythmias induced by pentylenetetrazol via the intravenous or the fourth ventricle route. Therefore, it is likely that these ganglionic blocking agents have also a central action similar to that at the peripheral autonomic ganglia.