Contractility of rat gubernacula affected by calcitonin gene-related peptide and beta-agonist.
OBJECTIVE
The effects of calcitonin gene-related peptide (CGRP), isoprenaline, and guanethidine on the neonatal rat gubernaculum were investigated in organ culture with the aim of seeing whether beta -agonists or beta -antagonists are involved in gubernacular development during testicular descent.


METHODS
A total of 200 gubernacula were studied. The gubernacula (n = 20 for each experiment) from male rat pups were incubated in aerated culture medium with isoprenaline (1 and 10 micromol/L) with/without CGRP (714 nmol/L) or guanethidine (1 and 10 micromol/L) with/without CGRP (714 nmol/L). Cultures were observed for 5 days by video camera to see spontaneous rhythmic contractions, which are known to correlate with normal gubernacular migration in the rodent.


RESULTS
Of gubernacula cultured without CGRP, 60% showed contractions by day 5, and the groups of isoprenaline and 10 micromol/L guanethidine showed similar rates, but only 15% of the 1 micromol/L guanethidine group showed contractility (P < .005). In contrast, of the gubernacula cultured with CGRP, each group showed high contractility from day 2 of the culture, and there was no difference between each group and the CGRP-alone group.


CONCLUSIONS
Although the beta -blocker showed a weak inhibitory effect on de novo gubernacular contractility, CGRP had a stronger effect on contractility, overriding any possible effects of the beta -neuron pathway. The contractility of the rat gubernaculum during testicular descent is primarily mediated by the genitofemoral sensory nerve fibers via release of CGRP, but beta -adrenergic nerves also may be involved.
Tomiyama
Hideki
H
F. Douglas Stephens Surgical Research Laboratory, Murdoch Childrens Research Institute, Parkville, Victoria 3052, Australia.
Hutson
John M
JM
D018663:Adrenergic Agents / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000502:physiology*; D003456:Cryptorchidism / Q000503:physiopathology; D006145:Guanethidine / Q000494:pharmacology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D013737:Testis / Q000196:embryology
D018663:Adrenergic Agents; D000318:Adrenergic beta-Agonists; D015740:Calcitonin Gene-Related Peptide; D007545:Isoproterenol; D006145:Guanethidine