The effect of intracerebroventricular injection of thyrotropin releasing hormone (TRH, 0.15 and 0.3 μg/5μl/rat) on response rates to intracranial self-stimulation (ICSS) was examined in the present study. Rats were trained to lever-press for ICSS with electrodes implanted in the ventral tegmental area (VTA). ICSS-response rates were markedly decreased by TRH (0.3 μg/5μl/rat, i.c.v.). Pimozide (0.15 mg/kg, i.p.), a dopamine blocker, antagonized the increased ICSS-response rates induced by methamphetamine (1 mg/kg, s.c.), but showed no effect on the decreased response rates induced by TRH (0.3 μg/5μl/rat). These results suggest that the TRH-induced suppression of ICSS may not be directly mediated by dopaminergic systems. Methysergide (1 mg/kg, i.p.), a serotonin blocker, which failed to affect the response rates by itself, blocked the TRH-induced suppression of ICSS. When 5-methoxy-N,N-dimethyltryptamine (0.1 mg/kg, i.p.), a direct serotonin receptor agonist, was administered in combination with TRH (0.15 μg/5μl/rat), ICSS-response rates were decreased, though each drug alone failed to change ICSS-response rates at the doses used. These results suggest that TRH may act on serotonergic systems and potentiate the serotonin neuronal transmission, and as a result, decrease ICSS-response rats.
|Number of pages||13|
|Journal||Research Communications in Psychology, Psychiatry and Behavior|
|Publication status||Published - 01-01-1989|
All Science Journal Classification (ASJC) codes
- Psychiatry and Mental health