Increase of spiny I activity in striatum after development of context-dependent sensitization of catalepsy in rats

In this study, it was investigated whether context-dependent sensitization of catalepsy changes the firing pattern in striatum. Rats were treated with either haloperidol (0.5 mg/kg i.p.) or saline, and tested on catalepsy with a concomitant single-unit measurement of the spiny I activity. Administration of haloperidol caused sensitization of catalepsy as measured on bar and grid. Concurrent within this behavioral change, spike-frequency increased over the course of the testing days in haloperidol-treated rats whereas the spike-frequency remained unchanged in saline-treated animals. Burst-frequency remained unchanged within both treatment groups over the days. In conclusion, sensitization of catalepsy is represented by striatal cellular activity as indicated by increases in spike-frequency of spiny I neurons.