Is the dopaminergic system involved in the central effects of nicotine in mice?

Pretreatment with ineffective doses of the D₁ antagonist SCH23390 but not the D₂ antagonist sulpiride reduced hyperactivity induced by nicotine in mice habituated to the test cage. On the other hand, the D₁ and D₂ antagonists were ineffective in blocking nicotine-induced hypoactivity in naive mice. Finally, SCH23390 and sulpiride did not block the antinociception induced by nicotine. Our data indicate that the dopamine receptors D₁ and D₂ are not involved in all the central effects of nicotine in mice, but seems to be a substrate for locomotor activation induced by nicotine under specific experimental conditions.