The effect of centrally administered TRH on blood pressure, heart rate and ventilation in rat

Different doses (3, 16, 80, 400 and 2 000 ng per rat) of TRH or alternatively saline were infused into the lateral ventricle of urethane-anaesthetized rats and blood pressure, heart rate, respiration rate and tidal volume were recorded. A dose of 3 ng TRH caused a significant elevation of blood pressure and heart rate, whereas 16 ng was needed for respiration rate to be elevated. There was no change in respiratory minute volume during the experiment. We conclude that TRH has profound physiological effects and that TRH, given centrally, is a potent hypertensive, chronotropic and tachypnoeic agent.