AUTONOMIC INNERVATION OF CAT ATRIA

¹ Department of Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York

Contractions were recorded from isolated electrically driven cat atria with bilateral vagal (VN) and sympathetic nerves (SN) attached. Inotropic responses to stimulation of each nerve were recorded before and after the following proccedures: 1) cutting off the upper portion of right atrium containing the sinoatrial (S-A) node; 2) procedure 1 followed by cutting off the lower half of the right atrium and atrial septum containing the atrioventricular (A-V) node; and 3) cutting off the left atrium and the interatrial septum. Responses to right VN and SN were reduced to to of control but were still present in both atria after procedure 1 or in the left atrium after procedure 2 but were unchanged in right atrium after procedure 3. Responses to left VN and SN were miot modified by procedure 1 or 2 but were abolished in right atrium after procedure 3. After right stellate ganglionectomy, chemical and histochemical determinations showed a decrease in endogenous norepinephrine content in both right and left atria and in both right and left ventricles. Left stellate ganglionectomy decreased norepinephrine in the left atrium and ventricle and to a lesser extent in the right atrium and ventricle. Unilateral VN stimulation shortened the total duration of the action potential markedly and to the same extent in the cells of the lateral ends in both right and left atrial appendages. Right VN stimulation produced a complete abolition of the S-A surface potential, with a limited A-V nodal activity occurring during this period. There was no A-V dissociation between S-A and A-V nodal activities during left VN stimulation.