The effect of long-term penfluridol treatment on the sensitivity of the dopamine receptors in the nucleus accumbens and in the corpus striatum.

The effect of local application of dopamine to the nucleus accumbens or corpus striatum on locomotor activity was studied in rats 4 days after withdrawal from a 6 weeks term of penfluridol medication. The bilateral application of dopamine into the nucleus accumbens of penfluridol-treated rats produced a very marked increase in coordinated locomotor activity which was 3-5 times higher than that of rats not treated with penfluridol. This effect of dopamine in both penfluridol-treated and control rats was antagonized by intraperitoneally administered haloperidol. The bilateral application of dopamine into the corpus striatum of penfluridol-treated animals produced a marked stereotyped behavioural syndrome in all rats studied, whereas no signs of stereotyped behaviour were observed in any of the rats not treated with penfluridol. The results indicate that long-term treatment of rats with the dopamine receptor blocking agent penfluridol produces an increase in the sensitivity of the dopamine receptors in the nucleus accumbens and corpus striatum and that the nucleus accumbens may play a role in locomotor activity.