Stereotypies elicited by injection of N-propylnorapomorphine into striatal subregions and nucleus accumbens

Abstract

Injection of the dopamine (DA) agonist R-(-)-N-n-propylnorapomorphine (NPA; 5-40 micrograms) into anterior ventral striatal sites (either lateral (VL) or medial (VM) elicited dose-dependent oral and sniffing stereotypies of rapid onset, long duration and high intensity. In contrast, injection into anterior dorsolateral (DL) or posterior ventral (lateral (PL) or medial (PM] sites produced little oral and moderate sniffing behavior of slower onset, shorter duration and low intensity. Injection into the dorsomedial (DM) striatum produced intermediate effects. Intra-accumbens NPA elicited weak oral activity and moderate sniffing which was similar in onset, duration and intensity to the least sensitive striatal sites (DL, PM and PL). In other experiments, DA receptors were inactivated with the irreversible blocking agent N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ; 6 mg/kg) and behavioral recovery was monitored by challenge with 20 micrograms NPA into the VL or the nucleus accumbens (NA) at various times after EEDQ. Sniffing behavior recovered rapidly (normal by day 4 in both regions), whereas oral activity required 8 (NA) and 12 days (VL) to return to control levels. The results are discussed in terms of a possible topographic distribution of behavior in the striatum. Alternatively, heterogeneity of DA receptor density may account for these findings.