Differential distribution of vanilloid receptors in the primary sensory neurons projecting to the dorsal skin and muscles

Abstract

We examined transient receptor potential (TRP) V1 and TRPV2 expression in calcitonin gene-related peptide (CGRP) positive (+) primary sensory neurons projecting to the skin and skeletal muscles of the rat dorsum. Among the dorsal root ganglia at the levels from C2 to Th1, 34.9% of neurons projecting to the skin were positive for CGRP, and 32.6% or 21.6% of neurons projecting to the trapezius muscle or the longissimus muscle were positive for CGRP. Of the small CGRP+ neurons projecting to the skin, 53.5% were positive for TRPV1, 11.6% were positive for TRPV2. Of the small CGRP+ neurons projecting to the trapezius or the longissimus, 53.1 or 53.2% were positive for TRPV1, 8.8 or 8.3% were positive for TRPV2, respectively. In the periphery, 29.3% of CGRP+ nerve fibers were positive for TRPV1 in the skin, whereas 65.0 or 59.8% were positive in the trapezius or the longissimus. Therefore, the present study showed that the percentage of CGRP+ neurons projecting to the trapezius is higher than that to the longissimus, and that the co-localization percentage of CGRP and TRPV1 on the sensory nerves was also higher in the trapezius than in the longissimus and the skin.

Sources of the motor and somatic sensory innervation of the trapezius muscle in the rat

“…In our studies the average number of FB + SPG neurons equals 2309 per animal in ipsilateral ganglia. Such a difference may be the result of the larger amount of tracer used in our study (10 µl of 5% FB suspension in our studies versus 5 µl 2% FB suspension in the study of Tsukagoshi et al, 2006) or longer post-surgery survival period. In the experiments of Tsukagoshi et al (2006) animals were sacrificed seven days after tracer injection, whereas in our studies ganglia were collected five weeks after surgery.…”

“…Such a difference may be the result of the larger amount of tracer used in our study (10 µl of 5% FB suspension in our studies versus 5 µl 2% FB suspension in the study of Tsukagoshi et al, 2006) or longer post-surgery survival period. In the experiments of Tsukagoshi et al (2006) animals were sacrificed seven days after tracer injection, whereas in our studies ganglia were collected five weeks after surgery. In the available literature there are no data regarding contralaterally located sensory neurons innervating trapezius muscle, but it has been reported in papers regarding the smooth retractor penis muscle of the pig (Panu et al, 2003), and the striated bulbospongiosus muscle of the pig (Botti et al, 2009).…”

“…Sensory innervation of studied muscle was accomplished by neurons located within the ipsi-and contralateral spinal ganglia extending from the C 2 to Th 3 spinal medulla segments. In the available literature there is no data regarding this problem in the rat except the paper by Tsukagoshi et al (2006). It was found that sensory neurons supplying the trapezius muscle were located in SPG-s extending from C 2 to Th 1 (Tsukagoshi et al, 2006).…”

“…In the available literature there is no data regarding this problem in the rat except the paper by Tsukagoshi et al (2006). It was found that sensory neurons supplying the trapezius muscle were located in SPG-s extending from C 2 to Th 1 (Tsukagoshi et al, 2006). Unfortunately, only ipsilateral ganglia were studied.…”

“…In regard to sensory innervation of the trapezius muscle the body of evidence is very limited. From the paper by Tsukagoshi et al (2006) it is known that sensory neurons supplying the trapezius muscle are localized in spinal SPG-s from C 2 to Th 1 . As mentioned previously, the trapezius muscle is involved in maintaining body balance.…”