Brief communication. Inability of hexamethonium to block the discriminative stimulus (SD) property of nicotine.

Rats were trained to discriminate between levers on a white or black wall to obtain food reinforcement, using nicotine or saline administration as the discriminative stimulus (SD). When hexamethonium was administered, either peripherally or intraventricularly, before the nicotine injection these rats responded as though they had received nicotine alone. This indicates that nicotine receptors responsible for its SD property are not blocked by hexamethonium, or alternatively that it is necessary to block the peripheral and central actions simultaneously to completely eliminate the cueing effect of the nicotine injection.