Nicotine reverses hemorrhagic shock in rats.

Cholinergic mechanisms are currently thought to play an essential role in blood pressure homeostasis. Here we show that, in urethane-anaesthetized rats bled to severe hemorrhagic shock, the i.v. administration of nicotine 0.2-50 micrograms/kg causes a prompt, sustained and dose-dependent improvement in cardiovascular and respiratory functions, the animals' survival rate being significantly higher than that of animals treated with saline. These effects are prevented by bilateral cervical vagotomy and by concurrent local anaesthesia of the carotid bodies, which suggests that stimulation of visceral afferents is the main mechanism of action of nicotine in hemorrhagic shock.