Involvement of central noradrenergic system in thyrotropin-releasing hormone-induced behavioral excitement in 6-OHDOPA-treated, infant rats.

A subcutaneous (s.c.) injection of thyrotropin-releasing hormone (TRH) 20 mg/kg, produced body shake and struggle, consequently induced an increase of count in ANIMEX activity meter in 7-day-old rats pretreated with 6-hydroxydopa (6-OHDOPA), 75 mg/kg, on days 0, 2 and 4. TRH-induced behavioral excitement was markedly attenuated in the infant animals which were injected desmethylimipramine, 5 mg/kg, 30 min before 6-OHDOPA on days 0, 2 and 4. It is suggested that central catecholaminergic, in particular, noradrenergic system is involved in TRH-induced body shake and struggle in 6-OHDOPA-treated, infant rats.