Dopaminergic control of striatal 5-HT level at normobaric condition and at pressure.

High pressure of helium-oxygen (He-O2) increases the extracellular levels in both serotonine and dopamine in the rat striatum. Some motor symptoms evoked by high pressure (i.e., LMA) are known to be reduced by intrastriatal infusions of D1-like (SCH23390, 1 microM) or D2-like (Sulpiride, 1 microM) dopaminergic antagonists. Other studies have also reported that serotoninergic antagonists reduce the motor perturbation at pressure. However, it remains unknown whether the changes in serotoninergic neurotransmission may contribute to the beneficial effects of intrastriatal administration of a dopaminergic antagonist. The present study reports the effects of SCH23390 and sulpiride on serotonin levels in the striatum of rats exposed to 8 MPa of He-O2. Both sulpiride and SCH23390 reduced pressure-induced striatal 5-HT increase. Our data suggest that D1-like and D2-like receptors have similar effects on a pressure-evoked striatal 5-HT increase. Thus, reduction in serotoninergic neurotransmission may be one mechanism by which dopaminergic antagonists reduce motor symptoms at pressure.