The role of sympathetic innervation in the developing rat gubernaculum.
BACKGROUND
Testicular descent occurs in several steps, but the mechanism remains unknown. Recently, sympathetic nerves have been proposed to have a role. This study aimed to see if adrenergic agonists and antagonists affected the neonatal rat gubernacular cremaster sac in organ culture.


METHODS
Cremaster sacs were collected from 2-day-old Sprague-Dawley male rats (n = 90) and placed in organ culture with/without (1) calcium chloride (0.45-1.8 mmol/L), (2) rat calcitonin gene-related peptide (CGRP) (714 nmol/L), (3) nifedipine (0.1-100 nmol/L), (4) isopreneline (10 micromol/L), and (5) guanethidine (10 micromol/L). Gubernacula were observed over 2 days for rhythmic peristalsis (>120 beats per minute for >1 minute).


RESULTS
Addition of CGRP stimulated rhythmic contractility but only in the presence of calcium, with a dose-response to the level of calcium ions. Contractions induced by CGRP with calcium could be obliterated in a dose-response by nifedipine. Isoprenaline caused some increase in contractions with calcium but less than that seen with CGRP. No augmentation of effect was seen with CGRP and isopreneline together, and the level of contractility was the same with guanethidine.


CONCLUSIONS
Calcitonin gene-related peptide is the main effector for contractility of the rat cremaster sac, as long as calcium ions are present. Adrenergic agonists and antagonists had limited effects. Contractility could be inhibited with nifedipine, consistent with CGRP acting via a calcium-dependent pathway.
Sasaki
Yasunari
Y
F Douglas Stephens Surgical Research Laboratory, Murdoch Childrens Research Institute, Parkville, 3052 Victoria, Australia.
Hutson
John M
JM
Clarke
Melanie C C
MC
D000818:Animals; D000831:Animals, Newborn; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D002122:Calcium Chloride / Q000494:pharmacology*; D003456:Cryptorchidism / Q000503:physiopathology; D004305:Dose-Response Relationship, Drug; D006145:Guanethidine / Q000494:pharmacology; D008297:Male; D023421:Models, Animal; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects; D009142:Musculoskeletal Physiological Phenomena; D009543:Nifedipine / Q000494:pharmacology; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012680:Sensitivity and Specificity; D013564:Sympathetic Nervous System; D013737:Testis / Q000196:embryology* / Q000294:innervation
D009543:Nifedipine; D015740:Calcitonin Gene-Related Peptide; D002122:Calcium Chloride; D006145:Guanethidine