The role of substance P and calcitonin gene-related peptide in neurogenic plasma extravasation and vasodilatation in the rat

Degeneration of motor nerve fibers enhances the expression of calcitonin gene-related peptide in rat sensory neurons

Calcitonin gene-related peptide (CGRP) in skeletal muscle is of neural origin. After degeneration of sensory fibers induced by removal of the lumbar dorsal root ganglia (DRG), the CGRP content in the rat soleus muscle was reduced to about 5% of the normal level. In contrast, degeneration of motor fibers induced by sectioning of the lumbar ventral roots markedly increased the CGRP content in the soleus muscle and CGRP levels in the lumbar DRG. It is suggested that the expression of CGRP in sensory neurons is up-regulated by some humoral factor induced by degeneration of motor nerve fibers.

Neural changes in acute arthritis in monkeys. III. Changes in substance P, calcitonin gene-related peptide and glutamate in the dorsal horn of the spinal cord

The effects of an experimentally induced arthritis on immunoreactivity of putative primary afferents neurotransmitter/neuromodulators were examined. Immunoreactive staining for substance P (SP), calcitonin gene-related peptide (CGRP) and glutamate (Glu) in the monkey dorsal horn was examined following inflammation of one knee joint induced by injection of 5% kaolin and 5% carrageenan. Spinal cords were examined at different time periods after induction of arthritis (2.5, 4, 6 and 8 h). Side to side differences in immunoreactivity were determined by a computer assisted quantitation system. A significant overall decrease in immunoreactivity of the lumbar versus the cervical dorsal horn was found for SP. The decrease for SP showed maximal changes of 68.3% at 4 h and 54.7% at 6 h. Immunoreactivity for CGRP was decreased 31.5% at 8 h and variable at other time points. Immunoreactivity for Glu, showed an ipsilateral increase of 31.4% at 4 h, 33.7% at 6 h, 39.9% at 8 h and a significant effect for lumbar versus cervical. Repetitive peripheral stimulation of the joint was shown to be important for changes in SP and Glu immunoreactivity. Without frequent peripheral stimulation in the early stages of the development of arthritis, SP showed no quantitative side to side differences. Increases in Glu immunoreactivity were present but not as prominent with minimal joint manipulation. These studies suggest that Glu may be involved in the aching pain of inflammation at rest whereas SP, CGRP and Glu may mediate pain induced by joint movement.

Ultraviolet irradiation of the skin attenuates calcitonin gene-related peptide mRNA expression in rat dorsal root ganglion cells

Calcitonin gene-related peptide (CGRP) mRNA expression in rat dorsal root ganglion cells was measured by polymerase chain reaction after ultraviolet (UV) irradiation of the skin. The aim was to investigate whether a noninvasive peripheral lesion set by UV irradiation influences neuropeptide gene expression thus possibly contributing to the pathophysiology of the UV erythema. Forty-eight hours after irradiation, when the inflammatory response of the skin was at its maximum, there was a decrease in CGRP mRNA levels to 50% of the control values. The results demonstrate that exposure of the peripheral receptive field to noxious UV radiation affects neuropeptide gene expression in primary sensory neurons.

Release of calcitonin gene-related peptide from nerve terminals in rat skeletal muscle

1. The amount of calcitonin gene-related peptide (CGRP) released from the isolated rat soleus muscle was measured by enzyme immunoassay. 2. When the soleus muscle was exposed to a solution containing high K+ (20-100 mM) in the presence of tetrodotoxin, the amount of CGRP released into the bathing medium increased with an increase in the K+ concentration. 3. The exposure to 100 mM-K+ did not increase CGRP release from chronically denervated soleus muscles or from pieces of the soleus nerve separated from the muscle. 4. The amount of CGRP released from the isolated muscle by 100 mM-K+ depended on the external Ca2+ concentration. The slope of the relation between the amount of CGRP release and the Ca2+ concentration was less than one on double logarithmic co-ordinates. 5. Following chronic section of the lumbar ventral roots, the mean amount of CGRP released from the soleus muscle by 100 mM-K+ was reduced by 28%, compared with that observed in normal muscle. 6. Antidromic stimulation of the lumbar dorsal roots at an intensity three times the threshold for most excitable sensory fibres failed to induce CGRP release from the soleus muscle, whereas stimulation at intensities 50-100 times the threshold increased significantly the amount of CGRP release from the muscle. 7. Stimulation of the muscle nerve at an intensity sufficient to activate the alpha-motor fibres did not release CGRP from the soleus muscle or from the diaphragm. 8. It is concluded that the major source of CGRP released from skeletal muscle is A delta- and/or C sensory terminals and that the Ca2+ dependence of CGRP release is less steep than that reported for acetylcholine release at neuromuscular junctions.

Immunization with calcitonin gene-related peptide reduces the inflammatory response to adjuvant arthritis in the rat

The influence of circulating antibodies to calcitonin gene-related peptide on the inflammatory response was examined in rats with adjuvant-induced arthritis. Rats were immunized with alpha calcitonin gene-related peptide conjugated to thyroglobulin, and circulating antibodies were identified by their capacity to bind radiolabelled rat alpha or human calcitonin gene-related peptide. In unimmunized rats and rats immunized with thyroglobulin alone, the secondary lesions (characterized as paw swelling, nodules on ears and tail, and inflamed nose) produced after adjuvant-induced arthritis were similar. However, at 21 days, when these lesions were maximal, the animals immunized with calcitonin gene-related peptide showed decreased numbers of lesions. An additional marker of disease activity, namely alpha 1 glycoprotein levels in plasma, was also measured. Again, plasma alpha 1 glycoprotein levels were similar in rats that were unimmunized or received thyroglobulin alone, but at 21 days were significantly reduced in animals immunized with calcitonin gene-related peptide. In contrast, the initial foot swelling seen in the first few days after injection of adjuvant was not significantly different in the various groups. The results suggest that antibodies to calcitonin gene-related peptide are able to reduce the severity of the adjuvant arthritis syndrome, and that this peptide contributes to the inflammatory response seen in the later stages of the disease model.