Locomotor activity in rats after administration of nicotinic agonists intracerebrally.

1. Nicotine (0.13 and 0.4 mg kg-1, s.c.) increased the ambulatory component of locomotor activity in rats previously exposed to the drug. Nicotine did not increase repeated movements reliably. 2. An infusion of either nicotine (8 micrograms) or the potent nicotinic agonist cytisine (4 micrograms) into the ventral tegmental area of the forebrain increased ambulation but not repeated movements. 3. An infusion of nicotine or cytisine into the nucleus accumbens, striatum, dorsal hippocampal formation or motor thalamus did not increase ambulatory or repeated movements. 4. Mecamylamine (0.1-1.0 mg kg-1, s.c.) blocked increases in locomotor activity produced by an infusion of nicotine or cytisine into the ventral tegmental area. 5. The locomotor activity produced by systemically administered nicotine may be mediated, in part, through nicotinic receptors located in the ventral tegmental area of the mesolimbic dopamine system.