Dopamine receptors in the pars reticulata of the substantia nigra were
inactivated following bilateral injections of N-ethoxycarbonyl-2-etho
xy-1,2-dihydroquinoline (EEDQ). Loss of D-1, but not D-2, receptors wa
s associated with a significant decrease in the incidence of stereotyp
ed head-down sniffing elicited by the mixed D-1/D-2 receptor agonist,
apomorphine. The results support the hypothesis that D-1 receptors in
the substantia nigra are necessary for the expression of dopamine medi
ated stereotyped behaviour.