Influence of thyrotropin-releasing hormone on general behavior and striatal [3H]spiperone binding in developing rats

An intraperitoneal administration of thyrotropin-releasing hormone (TRH, 2 or 20 mg/kg) produced behavioral excitement and consequently an increase in ANIMEX counts 15 min after the injection in a dose-dependent manner in 70-day-old rats. On the other hand, TRH (2 or 20 mg/kg)-induced behavioral excitement appeared more slowly (90-150 min) and more persistently in 7-day-old animals than in 70-day-old animals. TRH (2 or 20 mg/kg) significantly reduced specific [3H]spiperone binding to striatal membranes in 7- and 70-day-old rats compared to control, when the binding was examined in the membranes obtained from animals sacrificed 15 min and 150 min following TRH injection. In vitro addition of TRH up to 0.1 mM did not affect [3H]spiperone binding on days 7 and 70. From these results, it is suggested that striatal dopamine receptors could be involved in TRH-induced behavioral excitement in developing rats.