Localization of calcitonin gene-related peptide within the genitofemoral nerve in immature rats.
OBJECTIVE
Calcitonin gene-related peptide (CGRP) has been proposed to influence migration and testicular descent by release from the genitofemoral nerve. The site of CGRP within the nerve has been controversial, with conflicting views on whether CGRP is synthesised and released from the motor nerves.


METHODS
The genitofemoral nerve (GFN) was retrogradely labelled by fluorescent dye (DAPI) in 25 Sprague-Dawley rats (days 5, 16, and 31, n = 8 in each group; day 35, n = 1). Spinal cords and dorsal root ganglia (DRG) were removed two to three days later and sectioned for immunofluorescence. Substance P and CGRP-containing cells were labelled with fluorescein-linked antibodies. Specimens were examined by double fluorescence to identify cells with both markers.


RESULTS
The motor nucleus of the GFN contained 119 cells on day 7 and 284 cells by days 19 through 34. A prominent band of CGRP-containing fibers, arising from the dorsal horn, synapsed with the GFN motor nucleus itself. CGRP-labelled GFN cells were found in the DRG by double labelling.


CONCLUSIONS
CGRP from the GFN may affect gubernacular migration by release from the sensory nerves, rather than motor nerves as previously thought. The GFN motor nucleus receives CGRP-containing innervation from the dorsal horn, which may form part of the cremasteric reflex.
F. Douglas Stephens' Surgical Research Laboratory, Royal Children's Hospital Research Institute, Parkville, Victoria, Australia.
B
B
Schwindt
P J
PJ
Farmer
L M
LM
Watts
Z
Z
Hrabovszky
J M
JM
Hutson
D000818:Animals; D000831:Animals, Newborn; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis*; D005727:Ganglia, Spinal / Q000737:chemistry; D009046:Motor Neurons / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013127:Spinal Nerves / Q000737:chemistry*; D013373:Substance P / Q000378:metabolism
D013373:Substance P; D015740:Calcitonin Gene-Related Peptide