Physiological effects in vitro of calcitonin gene-related peptide on gubernacular contractility with or without denervation.
The gubernaculum in neonatal rats has been shown previously by direct observation to contract rhythmically in response to exogenous calcitonin gene-related peptide (CGRP), but the physiological properties of these contractions were unknown. In the first study the authors investigated gubernacular contractility in vitro using a strain gauge to see if there were characteristics of skeletal or smooth muscle. Both the frequency and the amplitude of contractions were significantly enhanced by CGRP, and isotonic tension of the gubernaculum and the duration of contractions were also increased after CGRP. The effect of CGRP on gubernacular contractions appeared several minutes after adding CGRP, and it was independent of the acetylcholine action, which induced only a single twitch response of the gubernaculum. In the second study the authors investigated the effect on gubernacular contractility of prior transection of the genitofemoral nerve (GFN), which contains CGRP. Vigorous contractions occurred in 85% of denervated gubernacular compared with 46% of controls (P < .01). These data provide the first quantitative evidence of rhythmic gubernacular contractions, and suggest that CGRP enhances gubernacular contractility by a direct effect independent of acetylcholine. Further, the contractile properties resemble those of differentiated cardiac muscle or primitive embryonic skeletal muscle. GFN transection enhances the gubernacular contractile response to exogenous CGRP, which is consistent with the GFN being the normal source of CGRP for the gubernaculum in vivo.
Shono
T
T
Surgical Research Unit, Royal Children's Hospital Research Foundation, Melbourne, Australia.
Goh
D W
DW
Momose
Y
Y
Hutson
J M
JM
D000818:Animals; D000831:Animals, Newborn; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology* / Q000502:physiology; D066298:In Vitro Techniques; D008022:Ligaments / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013737:Testis / Q000196:embryology*
D015740:Calcitonin Gene-Related Peptide