Local modulation of the 5-HT release in the dorsal striatum of the rat: an in vivo microdialysis study.

Using in vivo microdialysis in freely moving rats, we examined the involvement of major striatal transmitters on the local modulation of the 5-HT release. Tetrodotoxin reduced the striatal 5-HT output to 15-20% of baseline. The selective 5-HT(1B) receptor agonist CP 93129 (50 microM) reduced (50%) and the 5-HT(2A/2C) receptor agonist DOI (1-100 microM) increased (220%) the 5-HT output. Neither GABA nor baclofen (100 nM-100 microM) altered the 5-HT output. The glutamate reuptake inhibitor L-trans-PDC (1-4 mM) raised 5-HT to 280% of baseline. This effect was not antagonized by the NMDA receptor antagonist MK-801 (0.5 mg/kg i.p.). Local MK-801 (10-100 microM) did not significantly alter the 5-HT output. Finally, neither carbachol (10-100 microM) nor quipirole (10 microM-1 mM) affected 5-HT. These data suggest that the striatal 5-HT release is influenced by local serotonergic and glutamatergic (but not GABAergic) inputs.