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After intracisternal injection, 140 nmol (48 g) of cocaine (but not lidocaine or procaine) evoked an increase in mean arterial pressure (MAP) of 41 mm Hg. The increase in MAP began within 1 min after injection and lasted 10 to 15 min. The pressor response to intracisternal injection of cocaine was not mediated through central ␣-adrenergic receptors, but intracisternal pretreatment with D1 or D2 dopamine receptor antagonists shortened the duration of the response. Pretreatment with intracisternal injection of hemicholinium-3 to deplete medullary acetylcholine produced a dose-dependent inhibition of the pressor and tachycardic responses to intracisternal injection of cocaine. Central pretreatment with hemicholinium-3 also inhibited the pressor response to intravenous injection of 0.5 mg/kg cocaine. Atropine pretreatment was only partly effective in blocking the pressor and tachycardic responses to intracisternal injection of cocaine. However, a single intracisternal injection of the nicotinic ganglionic receptor blocker hexamethonium inhibited the pressor response to cocaine administered intracisternally 24 h later, and on each of the following 4 days. The blocking effect of hexamethonium was not mimicked by the ␣7 selective antagonist methyllycaconitine or by the ␣4␤2 subtype-preferring antagonist dihydro-␤-erythroidine. The data suggest that the pressor response to cocaine is mediated by medullary acetylcholine release on to nicotinic receptors of the ganglionic type, enhancing the output of bulbospinal sympathetic premotor neurons. Our results provide new evidence for the prolonged inactivation of relevant central nicotinic receptors by nicotinic receptor antagonists, and suggest that such compounds might be used safely for cocaine overdose, as well as for antiabuse issues without the concern for autonomic side effects.The ability of cocaine to increase systemic blood pressure usually is considered to be commensurate with drug's pharmacological classification as an indirect-acting sympathomimetic amine. Whereas cocaine conforms to this classification both in the peripheral and central nervous systems, the role of the CNS in terms of blood pressure alterations has been debated (Knuepfer et al., 1993;Gillis et al., 1995;Bernards, 1996). In fact, agonists at central ␣ 2 -adrenergic receptors such as clonidine and ␣-methyldopa are effective antihypertensive drugs; and levodopa and other dopaminergic antiParkinson agents often produce orthostatic hypotension as a side effect. Also, systemic administration of cocaine has been reported to decrease sympathetic nervous activity (Knuepfer and Branch, 1992;Gillis et al., 1995;Abrahams et al., 1996). Yet, there have been instances when cocaine has been administered directly into the CNS, usually via the cerebrospinal fluid, that the drug elicits an increase in arterial blood pressure. However, based upon the requirement for relatively high doses to elicit a pressor response via the lateral ventricular route (Knuepfer et al., 1993), it is unlikely that forebrain str...