Neuronal nicotinic receptor subtypes: defining therapeutic targets.

Humans have appreciated the beneficial properties of the tobacco plant for thousands of years. These effects include alertness, reduced anxiety, muscle relaxation, and analgesia. Yet it has been less than two decades since the central actions of nicotine have been examined in earnest for potential therapeutic applications. In fact, the cholinergic systems, in comparison to other neurotransmitter systems of the body, have been relatively poorly exploited in terms of therapeutic agents, and the muscarinic cholinergic systems have been relegated mainly to the treatment of gastrointestinal disorders and glaucoma; for the nicotinic system, antagonists are used to induce muscle paralysis during certain surgical procedures. For both families of cholinergic receptors, widespread exploitation in terms of therapeutics has been limited by significant side effect profiles associated with available cholinergic drugs.