Effects of thyrotropin-releasing hormone and its analogue, NS-3, on blood pressure, heart rate, and serum catecholamine levels in rats.

1. Thyrotropin-releasing hormone (TRH) and its metabolically stable analog NS-3 (montirelin hydrate; [3R, 6R]-6-methyl-5-oxo-3-thiomorpholinyl carbonyl-L-histidyl-L-prolinamide tetrahydrate) produced dose-dependent increases in blood pressure, heart rate, and the levels of serum noradrenaline and adrenaline in rats. 2. The pressor and tachycardiac effects and increases in serum catecholamine levels caused by NS-3 were longer lasting, but not more potent than those caused by TRH. 3. NS-3 did not change the blood pressure, heart rate, or the serum catecholamine levels in either pithed or hexamethonium-pretreated rats.