[Effect of thyrotropin-releasing hormone (TRH) and its analog DN-1417 on scopolamine-induced impairment of short-term memory in rats].

The effects of a few drugs, which are known to activate central nervous system, on scopolamine-induced impairment of short-term memory (STM) were studied in a delayed alternation task in rats. Rats were initially trained using a delayed alternation task in which a forced run to one arm of a T-maze was followed by a free-choice run. A correct free-choice response was defined as a turn toward the arm opposite to that in the forced run, and was rewarded with food pellets. After repeated training of the 60 sec-delayed alternation task, the treatment with scopolamine (0.2 mg/kg, ip) at 20 min before the test resulted in a significant decrement in the correct response. The scopolamine-induced impairment of STM was significantly antagonized by DN-1417 (10 mg/kg, ip) given 1 hr before the test. However, TRH (3-30 mg/kg, ip) and methamphetamine (0.2-1.0 mg/kg, ip) did not improve the scopolamine-induced impairment in the task. In rats without treatment with scopolamine, these drugs did not affect the percent correct response. These results suggest that DN-1417 may have an improving effect on the impairment of STM induced by a decreased cholinergic activity.