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Increased calcitonin gene-related peptide-like immunoreactivity (CGRPLI) in spinal motoneurones after dorsal rhizotomy
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INCREASED CALCITONIN GENE-RELATED PEPTIDE-LIKE IMMUNOREACTIVITY (CGRPLI) IN SPINAL MOTONEURONES AFTER DORSAL RHIZOTOMY H. Taquet, J.J. Plachot*, E. Collin, M. Pohl, S. Bourgoin, J.C. Meunier*, F. Cesselin and M. Hamon, INSERM U288, CHU Piti~-Salp~tri~re, 75013 Paris and *LPTFCNRS, 31077 Toulouse, France. At the spinal level, CGRP is present both in primary afferent fibers terminating within the dorsal horn, and in motoneurones within the ventral horn. It is well established that dorsal rhizotomy markedly reduces CGRPLI in the dorsal horn, but little attention has yet been paid to CGRPLI in the motoneurones after this lesion. This problem was further examined by using both immunohistochemistry with specific anti-CGRP antibodies and a radioimmunoassay for the visualization and quantification of CGRPLI in the lumbar segments of the spinal cord 10 days after the unilateral (on the left side) section of L1-L6 dorsal roots in 4 month-old Sprague-Dawley rats. As expected, a dramatic reduction in the number of CGRPLI - fibers was found within the L1-L6 segments in the superficial layers (laminae1 and 2) of the dorsal horn ipsilaterally to the rhizotomy. Measurements of CGRPLI in the ispsilateral dorsal zone of the L1-L6 lumbar cord indicated a ~80% decrease in the peptide contents in lesioned rats as compared to sham-operated and intact animals. Within the ventral horn, immunostaining of motoneurones (lamina 9) was markedly enhanced on the operated side as compared to that noted on the intact side in lesioned rats and on both sides in intact or sham-operated animals. In agreement with this observation, a ~four-fold increase in the levels of CGRPLI was found in the ipsilateral versus the contralateral ventral zone of the L1-L6 lumbar cord in lesioned rats. These data indicated that CGRPLI in motoneurones could be influenced by primary afferent inputs to the dorsal horn.
28 TIME COURSEOF CAPSAICIN-EVOKED RELEASE OF CGRPFROMRAT SPINAL CORDIN VITRO. EFFECT OF CONCENTRATION AND MODULATION BY RUTHENIUM RED. J. DONNERERand R. AMANN, Department of Exp. & Clin. Pharmacology, University of Graz, Universit~tsplatz 4, A-8010 Graz, Austria In the rat superfused dorsal spinal cord s|ice preparation, the dose-effect relationship for total CGRPrelease evoked by sustained single capsaicin doses (26 min exposure) was very steep with a threshold at 0.06 ~ and a maximum at 0.3 ~ capsaicin. With concentrations of capsaicin within this range the slow decline of the release response in the presence of capsaicin did not seemto be affected by exhaustion of an available transmitter pool nor impaired by neuronal blockade. In contrast, with concentrations of capsaicin at 1.5 ~M and above, there was a much faster termination of the release response after the peak, most probably due to a loss of the secretion capacity caused by neuronal inactivation. When cumulative dose regimens for capsaicin were employed, release of CGRPcould be stimulated only up to a dose of I -1.5 ~/~ capsaicin; further increase in capsaicin concentration was ineffective. This was also most probably due to a loss of the secretion capacity caused by neuronal inactivation and not caused by depletion of a releaseable transmitter pool. In the presence of Ruthenium Red (2.5 ~ ) , the responses to low capsaicin concentrations were blocked. In contrast, the inactivation of the release process during the high capsaicin doses was not affected by Ruthenium Red. The results demonstrate, that under equilibrium conditions, capsaicin stimulates and, at higher concentrations, also inhibits release of CGRPfrom primary afferent nerves.
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INCREASED CALCITONIN GENE-RELATED PEPTIDE-LIKE IMMUNOREACTIVITY (CGRPLI) IN SPINAL MOTONEURONES AFTER DORSAL RHIZOTOMY H. Taquet, J.J. Plachot*, E. Collin, M. Pohl, S. Bourgoin, J.C. Meunier*, F. Cesselin and M. Hamon, INSERM U288, CHU Piti~-Salp~tri~re, 75013 Paris and *LPTFCNRS, 31077 Toulouse, France. At the spinal level, CGRP is present both in primary afferent fibers terminating within the dorsal horn, and in motoneurones within the ventral horn. It is well established that dorsal rhizotomy markedly reduces CGRPLI in the dorsal horn, but little attention has yet been paid to CGRPLI in the motoneurones after this lesion. This problem was further examined by using both immunohistochemistry with specific anti-CGRP antibodies and a radioimmunoassay for the visualization and quantification of CGRPLI in the lumbar segments of the spinal cord 10 days after the unilateral (on the left side) section of L1-L6 dorsal roots in 4 month-old Sprague-Dawley rats. As expected, a dramatic reduction in the number of CGRPLI - fibers was found within the L1-L6 segments in the superficial layers (laminae1 and 2) of the dorsal horn ipsilaterally to the rhizotomy. Measurements of CGRPLI in the ispsilateral dorsal zone of the L1-L6 lumbar cord indicated a ~80% decrease in the peptide contents in lesioned rats as compared to sham-operated and intact animals. Within the ventral horn, immunostaining of motoneurones (lamina 9) was markedly enhanced on the operated side as compared to that noted on the intact side in lesioned rats and on both sides in intact or sham-operated animals. In agreement with this observation, a ~four-fold increase in the levels of CGRPLI was found in the ipsilateral versus the contralateral ventral zone of the L1-L6 lumbar cord in lesioned rats. These data indicated that CGRPLI in motoneurones could be influenced by primary afferent inputs to the dorsal horn.
28 TIME COURSEOF CAPSAICIN-EVOKED RELEASE OF CGRPFROMRAT SPINAL CORDIN VITRO. EFFECT OF CONCENTRATION AND MODULATION BY RUTHENIUM RED. J. DONNERERand R. AMANN, Department of Exp. & Clin. Pharmacology, University of Graz, Universit~tsplatz 4, A-8010 Graz, Austria In the rat superfused dorsal spinal cord s|ice preparation, the dose-effect relationship for total CGRPrelease evoked by sustained single capsaicin doses (26 min exposure) was very steep with a threshold at 0.06 ~ and a maximum at 0.3 ~ capsaicin. With concentrations of capsaicin within this range the slow decline of the release response in the presence of capsaicin did not seemto be affected by exhaustion of an available transmitter pool nor impaired by neuronal blockade. In contrast, with concentrations of capsaicin at 1.5 ~M and above, there was a much faster termination of the release response after the peak, most probably due to a loss of the secretion capacity caused by neuronal inactivation. When cumulative dose regimens for capsaicin were employed, release of CGRPcould be stimulated only up to a dose of I -1.5 ~/~ capsaicin; further increase in capsaicin concentration was ineffective. This was also most probably due to a loss of the secretion capacity caused by neuronal inactivation and not caused by depletion of a releaseable transmitter pool. In the presence of Ruthenium Red (2.5 ~ ) , the responses to low capsaicin concentrations were blocked. In contrast, the inactivation of the release process during the high capsaicin doses was not affected by Ruthenium Red. The results demonstrate, that under equilibrium conditions, capsaicin stimulates and, at higher concentrations, also inhibits release of CGRPfrom primary afferent nerves.