Effects of thyrotropin- and corticotropin-releasing hormone on blood pressure and plasma catecholamines in the anesthetized rat.

The neuropeptides thyrotropin-releasing hormone (TRH) and corticotropin-releasing hormone (CRH) have been found to be potent stimulators of the autonomic nervous system in both experimental animals and humans. We studied the effects of different doses of CRH and TRH given intracerebroventricularly in the urethane-anesthetized rat and a single dose of CRH in the chloral hydrate-anesthetized rat to elucidate the effects of these peptides in the unconscious state. All TRH doses studied enhanced blood pressure and noradrenaline and adrenaline secretion. Surprisingly, there were no blood pressure increases following administration of 0.4, 1.3 and 1.7 nmol CRH. In general, there was a tendency for blood pressure to decrease with the largest drop observed after 1.7 nmol CRH. Our data suggest that only TRH clearly augments blood pressure and catecholamine secretion in the anesthetized animal, while CRH does not exert major effects under the two anesthetic conditions employed.