Distribution and origin of calcitonin gene-related peptide containing fibers in the skin of the rat

$137 OCCURRENCE, ORIGIN, ONTOGENY C A R O T I D B O D Y OF RATS. HISATAKE KONDO Kanazawa, 920, J A P A N

Department

AND

PLASTICITY

of A n a t o m y ,

OF C G R P - I M M U N O R E A C T I V E

School

of M e d i c i n e ,

Kanazawa

NERVES

IN T H E

University,

Numerous CGRP-immunoreactive n e r v e f i b e r s w e r e r e v e a l e d to o c c u r in the c a r o t i d b o d y of a d u l t rats. A degeneration study together with capsaicin t r e a t m e n t s h o w e d the i m m u n o r e a c t i v e f i b e r s to r e p r e s e n t p e r i p h e r a l p r o c e s s e s of the s e n s o r y n e u r o n a l s o m a t a l o c a t e d in the g l o s s o p h a r y n g e a l and v a g a l g a n g l i a and, to a m u c h l e s s e r e x t e n t , the s p i n a l g a n g l i a . The i m m u n o r e a c t i v e f i b e r s first a p p e a r e d at p o s t n a t a l d a y 3 and g r a d u a l l y i n c r e a s e d in n u m b e r , a t t a i n i n g the a d u l t p a t t e r n in d e n s i t y and d i s t r i b u t i o n by p o s t n a t a l w e e k 5. M o s t of the i m m u n o r e a c t i v e f i b e r s w e r e l o c a t e d in the i n t e r s t i t i a l s p a c e and a few of t h e m w e r e d i r e c t l y a p p o s e d to the c h i e f c e l l s w h e r e no m e m b r a n e s p e c i a l i z a t i o n s w e r e formed. In the c a r o t i d b o d i e s one w e e k a f t e r the s e v e r a n c e of e i t h e r the glossopharyngeal or the vagal n e r v e , C G R P - i m m u n o r e a c t i v e f i b e r s w e r e as n u m e r o u s as in the c o n t r o l , a l t h o u g h t h e y d e c r e a s e d in n u m b e r in s p e c i m e n s two d a y s a f t e r the o p e r a t i o n s . In s p e c i m e n s one w e e k a f t e r the s u p e r i o r c e r v i c a l g a n g l i o h e c t o m y w i t h the s i m u l t a n e o u s s e v e r a n c e of e i t h e r the g l o s s o p h a r y n g e a l or the vagal nerve, the i m m u n o r e a c t i v e f i b e r s w e r e m o r e n u m e r o u s t h a n the c o n t r o l . In e l e c t r o n m i c r o s c o p y of the s p e c i m e n s one w e e k a f t e r the o p e r a t i o n s , t h i n i m m u n o r e a c t i v e f i b e r s w e r e o f t e n seen to be p a r t i a l l y e n c l o s e d t o g e t h e r w i t h i m m u n o n e g a t i v e f i b e r s by t h i n S c h w a n n cell p r o c e s s e s w i t h o u t m e s a x o n s . These f i n d i n g s s u g g e s t t h a t b o t h the g l o s s o p h a r y n g e a l and the vagal C G R P - f i b e r s i n n e r v a t i n g the c a r o t i d b o d y h a v e a h i g h c a p a b i l i t y of r e g e n e r a t i o n to c o m p e n s a t e for the loss of e i t h e r one of the two n e r v e s by s u r g i c a l s e v e r a n c e , and t h a t the sympathectomy enhances their regeneration.

DISTRIBUTION AND ORIGIN OF CALCITONIN GENE'RELATEDPEPTIBE CONTAINING FIBERS IN THE SKIN OF THE RAT

AKEHI ISHIDA-YAHAHOTO', EMIKO SENBAAND HASAYATOHYAHA, 2nd I)epartment of Anatomy, Osaka University Hodical School, 4-3-5? Nakanoshillla, Kitaku Osaka 530,Japan I% has been reported that numerous caleitenin gene-related peptide (CGRP) -like immunoreactive ( I ) fibers are distributed in the skin, but their structure and origin have not been fully investigated. For better understanding of the morphological characteristics and functional roles of these fibers, we studied the CGRP-I fibers in the glabrous skin of the rat using an i~unohistochemical method. As Lo the origin of these fibers, the resection of the Q-Th2 or La-Le dorsal root ganglion(DRG) resulted in an almost complete disappearance of cutaneous CGRP-I fibers in the forefoot or foot, respectively. This result indicates that these fibers, including those around the vessels and the eccrine sweat glands, originated in the OR(;. In the DRG, not only small, but also medium- to large-sized neurons shoved imunoreactivity to CGRP. In order %o detect the DR(; neurons that innervate the skin, Fast Blue (FB) dye was injected into the sural nerve. Then 21.4~ of the CGRP-I neurons in the BRG (L4,s), of various sizes, were labeled with FB. In the skin, the CGRP-I varicose fibers were distributed in the epiderBis, and in the derBis, surrounding the vessels and the eccrine sweat glands. Host of the CGRP-I fibers in the epidermis and around the vessels showed substance P (SP) -1 ike imunore~ctivity at the same time, indicating that these fibers originate frol the SP-ilmunoreactive (SP-I) small-sized neurons. However, most of the CGRP-I fibers around the eccrine sweat glands did not show SP-like iBtunoreactivity, suggesting that they originate from non-SP-I DRG neurons. Imunoelectronmicroscopie observation of the CGRP-I fibers in the epidermis revealed that there was no synaptic contact hetween these fibers and the keratinocytes. In the Hoissner corpuscles, the mechanoreceptive nerve endings were devoid of imunoreactivity to CGRP. Though the CGRP-I varicose fibers were found inside about 15¢ of the Hoissner corpuscles, there was no synaptic contact with non-CGRP-I fibers. In Merkel's discs, the meehanoreceptive non-CGRP-I nerve endings made desmesoml junctions with Horkel cells. The CGRP-I fibers were apposed %o the flerkel cells, but no synaptic-1 ike structure was observed between them.