Thyrotropin-releasing hormone (TRH) and CNS regulation of anorectal motility in the rat.
The effect of thyrotropin-releasing hormone (TRH) upon anorectal motility was investigated in acute male rat preparations. Micromolar doses of TRH were intrathecally (i.t.) infused at the L6 spinal level at a rate of 1 microliter/min over 8 min. TRH infusions in 1.0-1000 microM concentrations elicited biphasic, dose-dependent anorectal contractions as measured by a rectal manometer. The 100 microM dose yielded the most significant increase in contractions over the greatest period of time. Atropine, administered as a pretreatment (100 micrograms s.c.), blocked contractions normally produced by i.t. infusion of TRH (1000 microM). Intravenous infusions of atropine (10 micrograms) through a jugular catheter immediately blocked anorectal contractions produced by i.t. infusion of 100 microM TRH. Sectioning of the hypogastric nerve, which supplies sympathetic innervation to the colon and internal anal sphincter, did not significantly affect contractions induced by 100 microM TRH applied intrathecally. Disruption of the major pelvic ganglion fibers, however, completely abolished the contractions induced by 100 microM TRH, either through the interruption of preganglionic parasympathetic fibers in the pelvic nerve, or by disrupting postganglionic fibers. These findings extend the role of TRH in the regulation of defecatory behaviors.
Holmes
G M
GM
Department of Cell Biology, Neurobiology and Anatomy, Ohio State University, Columbus, OH 43210-1239, USA.
Rogers
R C
RC
Bresnahan
J C
JC
Beattie
M S
MS
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003106:Colon / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005769:Gastrointestinal Motility / Q000187:drug effects*; D007278:Injections, Spinal; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D051381:Rats; D012018:Reflex / Q000187:drug effects*; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D013973:Thyrotropin-Releasing Hormone; D001285:Atropine