The central actions of nicotine on blood pressure and heart rate after administration via the left vertebral artery of anaesthetized cats. Distribution of nicotine into the brain after central application.

After injection into the vertebral artery of anaesthetized cats, low does of nicotine (10(-9)--10(-8) mol = 0.5--5 micrograms . kg-1) induce potent cardiovascular effects. The hypotensive action is always accompanied by a severe bradycardia. Dose-response curves for these pharmacological actions have been established. It is concluced that nicotinic receptors in the medulla oblongata and pons are involved. Administration of 10(-8) mol = 5 micrograms (radioactive) nicotine/kg into the left vertebral artery gives rise to a specific distribution pattern. Nicotine mainly accumulates into the ponto-medullary area, whereas higher brain regions (hypothalamus) contain only insignificant amounts. The experimental results suggest that the nicotine-like effect of endogenous acetylcholine might play an important physiological part in the central regulation of blood pressure and cardiac frequency.