5-HT(1A) and 5-HT(1B) receptors in the ventrolateral striatum differentially modulate apomorphine-induced jaw movements in rats.

The ability of serotonin 5-HT(1A) and 5-HT(1B) receptors in the ventrolateral striatum to modulate dopamine receptor-mediated jaw movements was investigated in freely moving rats, using a magnet-sensing system combined with an intracerebral drug microinjection technique. Apomorphine (1 mg/kg i.v.) has been found to elicit repetitive jaw movements. Bilateral injections of the 5-HT(1A) receptor agonist 8-OH-DPAT (1 and 4 microg/0.2 microl in each side) into the ventrolateral striatum partially but significantly reduced apomorphine-induced repetitive jaw movements. The 5-HT(1A) receptor antagonist WAY-100635 (1 microg), which alone did not affect the effects of apomorphine, antagonized the inhibitory effects of 8-OH-DPAT (4 microg). Bilateral injections of the 5-HT(1B) receptor agonist CP93129 (1 and 10 microg) also reduced apomorphine-induced repetitive jaw movements in a dose-dependent manner. However, the 5-HT(1B) receptor antagonist GR55562 (1 and 10 microg) did not antagonize the inhibitory effects of CP93129 (10 microg). These results suggest that 5-HT(1A), but not 5-HT(1B), receptors in the ventrolateral striatum play a modulatory role in the production of dopamine receptor-mediated jaw movements.