Burst activity of spiny projection neurons in the striatum encodes superimposed muscle tetani in cataleptic rats.

Catalepsy of animals represents a condition of akinesia and high rigidity of muscles. Catalepsy is a model for Parkinson's disease. The activity of spiny projection neurons in the striatum is correlated with different groups of muscles in rats or primates. Burst activity is a typical characteristic of spiny projection neurons in the state of Parkinson's disease. Rats were treated with 0.5 mg/kg haloperidol to induce a cataleptic state for 180 s. Spiny projection neuronal activity in striatum was measured to detect changes in spike frequency. Triggers were set manually when the rats increased their muscle tone superimposed on the already existing tetanus of the forelimb muscles. The results showed a clear correlation of the occurring triggers and the burst activity in the striatum. During such a burst event, rats did not move but showed this typical superimposed muscle tetanus. A possible explanation is that the intention to move is encoded in the burst activity of spiny projection neurons in the striatum while the execution of the movement is blocked. But also bursts that are not correlated with the short-term superimposed muscle tetanus occurred.