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Modulation of peptide release evoked by bradykinin and electrical field stimulation in guinea-pig atria
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NEUROPEPTIDES
the second part of capsaicin action is partially due to the release of SP in the system. On the other hand, chronic (0.21 &kg, daily for 10 days, i.p. or s.c.) capsaicin treated rats showed significant inhibition of SP, carragenan or capsaicin (a single dose of 50 p&kg) induced paw inflammation. The results indicate that the anti-inflammatory effect of capsaicin is not only local but also peripheral. Hence, both these results indicate the involvement of SP containing nerve fibres in capsaicin induced inflammatory and anti-inflammatory responses in the rat paw. These findings indicate the prospects of therapeutic use of capsaicin in Substance P mediated inflammatory responses. 1. De, A. K. and Ghosh, J. J. Phytotherapy research 2: 175 179 (1988). 2. De, A. K. and Ghosh, J. J. Phytotherapy research 4: 42-44 (1990).
pH-Induced Release of Calcitonin GeneRelated Peptide-Like Immunoreactivlty (CGRP-LI) From the Rat Isolated Soleus Muscle E. Del Bianco,
P. Santicioli
and C. A. Maggi
Dept. of Internal Medicine, University of Florence and Pharmacology Department A. Menarini Pharmaceuticals, Via Sette Santi 3, 5013 1 Florence,
Italy Increase in local proton concentration (lowering of pH) has been considered as a pathophysiologically relevant stimulus to activate release of sensory neuropeptides from peripheral terminals of capsaicin-sensitive primary afferents (1,2). We have assessed whether protons may be able to induce such a response in the rat isolated soleus muscle by measuring the outflow of CGRP-LI which was determined by radioimmunoassay (2). Application of capsaicin (10 ph4) or of low pH @H 6 or 5) media evoked a prompt outflow of CGRP-LI from the rat soleus muscle. Release evoked by pH 6 and 5 media averaged 26 and 73%, respectively of that evoked by capsaicin (233 f 27 finoV20 min, n = 12). CGRP-LI outflow evoked either by capsaicin or pH 5 was totally abolished by previous incubation in a calcium free medium containing EDTA. Previous application of capsaicin totally prevented the effect of a second application of the drug, indicating complete desensitization. After capsaicin desensitization, pH 5 medium was unable to evoke further CGRP-LI release. The effect ofboth capsaicinand pH 5 medium was blocked (70-85% inhibition) by ruthenium red (10 pM), a blocker of the cation channel coupled with the vanilloid receptor (3). These findings demonstrate that lowering of pH induces local release of CGRP from skeletal muscle through a ruthenium red-sensitive mechanism. Since CGRP is a powerful vasodilator and influences both acetylcholine release (4) and glycogen metabolism (5) in
skeletal muscle, this mechanism could be of importance for local regulation of blood flow and energy consumption during ischemia. 1.
Arvier, P. T., Chahl, L. A. and Ladd. R. J. (1977). Br. J. Pharmacol. 59: 61. 2. Geppetti, P., Del Bianco, E., Patacchini, R., Santicioii, P.. Maggi, C. A. and Tramontana, M. (1991). Neuroscience 41: 295. 3. Amann, R. and Maggi, C. A. (1991). Life Sci. 49: 849. 4. Jinnai, K., Chihara, K., Kanda, F., Tada, K. and Fujita, T. (1989). Neurosci. Letters 103: 64. 5. Leighton, B. and Cooper G. J. S. (1988). Nature 335: 632.
Modulation of Peptide Release Evoked by Bradykinin and Electrical Field Stimulation in Guinea-Pig Atria E. Del Bianco, P. Santicioli, P. Geppetti and C. A. Maggi Dept. of Internal Medicine, University of Florence and Pharmacology Department A. Menarini Pharmaceuticals, Via Sette Santi 3,50131 Florence, Italy Various stimuli, including electrical field stimulation (EFS) and bradykinin (BK) have been shown to induce release of sensory neuropeptides from peripheral endings of capsaicin-sensitive primary afferents in guinea-pig atrium. In particular, release of calcitonin gene-related peptide (CGRP) produced by both EFS and BK at this level is abolished by omega conotoxin (1,2), indicating a common mechanism of transmitter secretion. However the response to EFS is tetrodotoxin-sensitive while that to bradykinin is tetrodotoxin-resistant. Because of this difference we were interested in assessing whether CGRPlike immunoreactivity (CGRP-LI) produced by these two stimuli could be subjected to differential pharmacological modulation. Application of 10 pM BK or EFS (30 Hz, 10 V, 50 mA/cm2, 1 ms, 10 s train every 20 s) produced a prompt increase in CGRP-LI outflow from the guinea-pig atria which averaged 78 + 19 and 92 f 30 fmoligf20 min, respectively. Both morphine and neuropeptide Y (NPY) have been proposed to exert a prejunctional modulatory influence on CGRP release in the atrium (3,4). Morphine (3 pM) inhibited CGRP-LI release in the atrium evoked by EFS or BK by 88 f 8% and 66 f 3%, respectively. NPY (0.3 ph4) inhibited CGRP-LI release evoked by EFS and BK by 68 + 11% and 65 + 13%, respectively. The similar reduction in the CGFW release evoked by EFS (TTXsensitive) and BK (TTX-resistant) by morphine and NPY suggests that these agents exert a negative modulatory feedback at the very terminal region of sensory nerves. 1. 2. 3. 4.
Geppetti, P. et al. (1990). Neuroscience. 38: 687-692. Maggi, C. A. et al. (1989). Eur. J. Pharmacol. 170: 167-177. Giuliani, P. et al. (1989). Br. J. Pharmacol. 98: 407-412. Giuliani, P. et al. (1990). Gen. Phannacol. 163: 91-96.
NEUROPEPTIDES
the second part of capsaicin action is partially due to the release of SP in the system. On the other hand, chronic (0.21 &kg, daily for 10 days, i.p. or s.c.) capsaicin treated rats showed significant inhibition of SP, carragenan or capsaicin (a single dose of 50 p&kg) induced paw inflammation. The results indicate that the anti-inflammatory effect of capsaicin is not only local but also peripheral. Hence, both these results indicate the involvement of SP containing nerve fibres in capsaicin induced inflammatory and anti-inflammatory responses in the rat paw. These findings indicate the prospects of therapeutic use of capsaicin in Substance P mediated inflammatory responses. 1. De, A. K. and Ghosh, J. J. Phytotherapy research 2: 175 179 (1988). 2. De, A. K. and Ghosh, J. J. Phytotherapy research 4: 42-44 (1990).
pH-Induced Release of Calcitonin GeneRelated Peptide-Like Immunoreactivlty (CGRP-LI) From the Rat Isolated Soleus Muscle E. Del Bianco,
P. Santicioli
and C. A. Maggi
Dept. of Internal Medicine, University of Florence and Pharmacology Department A. Menarini Pharmaceuticals, Via Sette Santi 3, 5013 1 Florence,
Italy Increase in local proton concentration (lowering of pH) has been considered as a pathophysiologically relevant stimulus to activate release of sensory neuropeptides from peripheral terminals of capsaicin-sensitive primary afferents (1,2). We have assessed whether protons may be able to induce such a response in the rat isolated soleus muscle by measuring the outflow of CGRP-LI which was determined by radioimmunoassay (2). Application of capsaicin (10 ph4) or of low pH @H 6 or 5) media evoked a prompt outflow of CGRP-LI from the rat soleus muscle. Release evoked by pH 6 and 5 media averaged 26 and 73%, respectively of that evoked by capsaicin (233 f 27 finoV20 min, n = 12). CGRP-LI outflow evoked either by capsaicin or pH 5 was totally abolished by previous incubation in a calcium free medium containing EDTA. Previous application of capsaicin totally prevented the effect of a second application of the drug, indicating complete desensitization. After capsaicin desensitization, pH 5 medium was unable to evoke further CGRP-LI release. The effect ofboth capsaicinand pH 5 medium was blocked (70-85% inhibition) by ruthenium red (10 pM), a blocker of the cation channel coupled with the vanilloid receptor (3). These findings demonstrate that lowering of pH induces local release of CGRP from skeletal muscle through a ruthenium red-sensitive mechanism. Since CGRP is a powerful vasodilator and influences both acetylcholine release (4) and glycogen metabolism (5) in
skeletal muscle, this mechanism could be of importance for local regulation of blood flow and energy consumption during ischemia. 1.
Arvier, P. T., Chahl, L. A. and Ladd. R. J. (1977). Br. J. Pharmacol. 59: 61. 2. Geppetti, P., Del Bianco, E., Patacchini, R., Santicioii, P.. Maggi, C. A. and Tramontana, M. (1991). Neuroscience 41: 295. 3. Amann, R. and Maggi, C. A. (1991). Life Sci. 49: 849. 4. Jinnai, K., Chihara, K., Kanda, F., Tada, K. and Fujita, T. (1989). Neurosci. Letters 103: 64. 5. Leighton, B. and Cooper G. J. S. (1988). Nature 335: 632.
Modulation of Peptide Release Evoked by Bradykinin and Electrical Field Stimulation in Guinea-Pig Atria E. Del Bianco, P. Santicioli, P. Geppetti and C. A. Maggi Dept. of Internal Medicine, University of Florence and Pharmacology Department A. Menarini Pharmaceuticals, Via Sette Santi 3,50131 Florence, Italy Various stimuli, including electrical field stimulation (EFS) and bradykinin (BK) have been shown to induce release of sensory neuropeptides from peripheral endings of capsaicin-sensitive primary afferents in guinea-pig atrium. In particular, release of calcitonin gene-related peptide (CGRP) produced by both EFS and BK at this level is abolished by omega conotoxin (1,2), indicating a common mechanism of transmitter secretion. However the response to EFS is tetrodotoxin-sensitive while that to bradykinin is tetrodotoxin-resistant. Because of this difference we were interested in assessing whether CGRPlike immunoreactivity (CGRP-LI) produced by these two stimuli could be subjected to differential pharmacological modulation. Application of 10 pM BK or EFS (30 Hz, 10 V, 50 mA/cm2, 1 ms, 10 s train every 20 s) produced a prompt increase in CGRP-LI outflow from the guinea-pig atria which averaged 78 + 19 and 92 f 30 fmoligf20 min, respectively. Both morphine and neuropeptide Y (NPY) have been proposed to exert a prejunctional modulatory influence on CGRP release in the atrium (3,4). Morphine (3 pM) inhibited CGRP-LI release in the atrium evoked by EFS or BK by 88 f 8% and 66 f 3%, respectively. NPY (0.3 ph4) inhibited CGRP-LI release evoked by EFS and BK by 68 + 11% and 65 + 13%, respectively. The similar reduction in the CGFW release evoked by EFS (TTXsensitive) and BK (TTX-resistant) by morphine and NPY suggests that these agents exert a negative modulatory feedback at the very terminal region of sensory nerves. 1. 2. 3. 4.
Geppetti, P. et al. (1990). Neuroscience. 38: 687-692. Maggi, C. A. et al. (1989). Eur. J. Pharmacol. 170: 167-177. Giuliani, P. et al. (1989). Br. J. Pharmacol. 98: 407-412. Giuliani, P. et al. (1990). Gen. Phannacol. 163: 91-96.