Cardiovascular Effects of Repeated Nicotine Administrations: Conditions where Effects are Maintained or where Self-Blockade Takes Place

The pharmacologic conditions were examined where repeated doses of nicotine produce either sustained stimulant effects or self-blockade on the cardiovascular system. Repeated nicotine showed quantitatively maintained effects in unanesthetized spinal rats, at a dose range from 0.025 to 0.4 mg/kg i.v. Sodium pentobarbital (60 mg/kg i.p.) produced a tenfold decrease in sensitivity to single initial doses of nicotine and thus brought about a requirement of larger doses for cardiovascular stimulation. Nicotine self-blockade was observed only with very large doses under special conditions of pentobarbital anesthesia.