We investigated the effect of
taltirelin hydrate ((−)-N-[(S)-hexahydro-1-methyl- 2,6-dioxo-4-pyrimidinyl-carbonyl]-L-histidyl-L-
prolinamide tetrahydrate; taltirelin), a metabolically stable
thyrotropin-releasing hormone (TRH) analog, on circulatory function, respiratory function, and viable time after
bleeding in
urethane-anesthetized rats. Massive volume-controlled
bleeding caused marked reductions in mean arterial pressure (MAP) and respiratory rate (RR). The vital signs of control rats were lost within an average of 23 min after
bleeding.
Intravenous administration of taltirelin (0.03−0.3 mg/kg) and TRH (1 and 3 mg/kg) immediately after
bleeding accelerated recovery of MAP and RR, and prolonged viable time in a dose-dependent manner. The potency of taltirelin in accelerating MAP and RR recovery and prolonging viable time was higher when compared with that of TRH. In addition, recovery of MAP and RR and the extension of viable time by taltirelin were inhibited by preintraperitoneal administration of
atropine sulfate, which is a centrally acting
muscarinic antagonist, but not by that of
atropine methylbromide, which is a peripherally acting
muscarinic antagonist. Taltirelin also recovered decreased arterial pH,
bicarbonate ions, and base excess, and prevented a decrease in arterial oxygen saturation. In conclusion, the anti-
shock effect of taltirelin was more potent than that of TRH. Taltirelin activity was mediated by the central
muscarinic cholinergic system. In addition, taltirelin also corrected
metabolic acidosis. These results suggest that taltirelin could be useful in the treatment of
hypovolemic shock.