Urocortin 3 Microinjected Into The Intermediolateral Cell Column Elicits Tachycardia In The Rat

Abstract

Urocortin 3 (Ucn 3) is a new member of corticotropin releasing factor (CRF) family of peptides. There is limited information about the cardiovascular actions of this peptide. Urethane‐anesthetized, artificially ventilated, adult male Wistar rats, weighing between 325‐350 gm, were used in this study. L‐Glutamate (L‐Glu; 5 mM), microinjected (30 nl) into the right intermediolateral cell column (IML) at T1 or T2 level, elicited an increase (35 ± 4 bpm) in heart rate (HR). The onset and duration of these responses was 5 and 50‐60 sec, respectively. Microinjections (30 nl) of Ucn 3 (0.31, 0.62, 0.12 and 0.25 mM) into the same sites in the IML elicited tachycardia; the increases in HR were 13.6 ± 1.5, 31.8 ± 3.9, 37.9 ± 2.1 bpm and 33.6 ± 3.4 bpm, respectively. Maximum tachycardic responses were elicited by 0.12 mM concentration of Ucn 3. The tachycardic responses elicited by Ucn 3 (0.12 mM) were significantly attenuated by prior microinjections (30 nl) of a selective antagonist (K41498, 1 mM) for CRF type 2 receptors. It was concluded that Ucn 3 exerts an excitatory effect on IML neurons controlling cardiac function.Support: NIH grants HL024347 and HL076248.