Cardiovascular effects of zimelidine and tricyclic antidepressants in conscious rats.

Blood pressure, heart rate and electrocardiograms were recorded in conscious rats during intravenous injections of consecutively increasing doses of zimelidine, amitriptyline, clomipramine, desipramine and imipramine. The tricyclic antidepressants (TCA's) increased blood pressure from low doses and induced shortlasting decreases in blood pressure at higher doses. Heart rate was initially increased by amitriptyline while the other TCA's tended to decrease heart rate dose-dependently. The TCA's prolonged the QRS and QT intervals dose-dependently from low doses and the PR interval from intermediate doses. Zimelidine did not affect blood pressure or heart rate until high doses were given. The PR interval was not affected by zimelidine. Moderate to high doses of zimelidine prolonged the QT length and high doses widened the QRS complex. The results indicate a good cardiovascular tolerance for zimelidine.