Antagonism of neurotensin induced miosis by thyrotropin-releasing hormone (TRH) in rabbits.
In previous studies we have shown that thyrotropin-releasing hormone (TRH) antagonizes many of the neural effects of neurotensin (NT). This study, evaluated the ability of TRH and two TRH analogs: 3 methyl-His-TRH and Phe2-TRH to affect NT-induced miosis in rabbits. In confirmation of previous findings, NT (30 micrograms) produced a significant miosis. The high (60 micrograms), but not the low (30 micrograms) dose of TRH significantly antagonized NT (30 micrograms)-induced miosis. Of interest was the observation that 3 methyl-His-TRH and Phe2-TRH were more effective than native TRH in blocking NT-induced miosis. The inhibitory effect of 3 methyl-His-TRH on the miotic response to NT exhibited long duration (approximately 60 min) when compared to native TRH and Phe2-TRH. TRH or the TRH congeners had no appreciable effects on pupillary diameter when administered alone. These findings indicate that TRH antagonizes the miotic response to NT, and suggest a hitherto undescribed peptide-peptide interaction involved in regulation of iris motility.
Hernandez
D E
DE
Department of Medicine, University of Southern California, Los Angeles.
Simons
K B
KB
Spampinato
D
D
Jennes
L
L
D000818:Animals; D008297:Male; D009496:Neurotensin / Q000502:physiology*; D011680:Pupil; D011817:Rabbits; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000502:physiology*
D009496:Neurotensin; D013973:Thyrotropin-Releasing Hormone