Genetic fuzzy system predicting contractile reactivity patterns of small arteries

Monitoring of physiological surrogate end points in drug development generates dynamic time-domain data reflecting the state of the biological system. Conventional data analysis often reduces the information in these data by extracting specific data points, thereby discarding potentially useful information. We developed a genetic fuzzy system (GFS) algorithm that is capable of learning all information in time-domain physiological data. Data on isometric force development of isolated small arteries were used as a framework for developing and optimizing a GFS. GFS performance was improved by several strategies. Results show that optimized fuzzy systems (OFSs) predict contractile reactivity of arteries accurately. In addition, OFSs identified significant differences that were undetectable using conventional analysis in the responses of arteries between groups. We concluded that OFSs may be used in clustering or classification tasks as aids in the objective identification or prediction of dynamic physiological behavior

The Effect of Calcitonin Gene-Related Peptide (CGRP) on the Cytosolic Calcium Concentration and Force in Rat Intramural Coronary Arteries

The aim of this study was to investigate the mechanism of CGRP-induced relaxation in intramural rat coronary arteries. By using FURA-2 technique, cytosolic Ca2+-concentration ([Ca2+]i) was measured during contraction of the vascular smooth muscle with receptor-dependent agonist (tromboxane A2 analogue U46619) and with high concentration of extracellular potassium. At a steady state of contraction, the increase in [Ca2+]i induced by 300 nM U46619 (100״x 14 nM, n = 7) was similar to that induced by 36 mM K+ (98 ״x 9 nM, n = 7). However, the active tension induced by 300 nM U46619 was significantly (p < 0.01) higher than that induced by 36 mM K+. CGRP concentration-dependently (10 pM - 10 nM) reduced both the [Ca2+]i and tension of coronary arteries precontracted with either U46619 or BAY K 8644, and also of resting coronary arteries in PSS. In 36 mM K+-depolarized arteries, CGRP reduced only the tension without affecting the [Ca2+]i. In 300 nM U46619 precontracted arteries, pretreatment with 10 μM thapsigargin significantly (p < 0.05) attenuated the CGRP-induced reduction in the tension (but not [Ca2+]i). In 300 nM U46619 precontracted arteries, pretreatment with either 100 nM charybdotoxin or 100 nM iberiotoxin or 10 nM felodipine significantly (p < 0.05) attenuated the CGRP-induced reduction in both [Ca2+]i and the tension. In contrast, 1 μM glibenclamide did not affect the CGRP-induced responses in these coronary arteries. In resting coronary arteries, only pretreatment with the combination of 1 μM glibenclamide and 100 nM charybdotoxin attenuated the CGRP-induced decrease in the [Ca2+]i and tension, suggesting a different mechanism of action for CGRP in resting coronary arteries. We conclude that CGRP relaxes precontracted rat coronary arteries via three mechanisms: (1) a decrease in [Ca2+]i by inhibiting the Ca2+ influx through membrane hyperpolarization mediated partly by activation of BKCa channels, (2) a decrease in [Ca2+]i presumably by sequestrating cytosolic Ca2+ into thapsigargin-sensitive Ca2+ storage sites, and (3) a decrease in the Ca2+ -sensitivity of the contractile apparatus

Noncompetitive antagonism of BIBN4096BS on CGRP-induced responses in human subcutaneous arteries

1 We investigated the antagonistic effect of 1-piperidinecarboxamide, N-[2-[[5amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl]pentyl]amino]-1 -[(3,5-dibromo-4-hydroxyphenyl)methyl]-2-oxoethyl]4-(1,4- dihydro-2-oxo-3(2H)-quinazolinyl) (BIBN4096BS) on the calcitonin gene-related peptide (CGRP)-induced responses by using isometric myograph and FURA-2 technique in human subcutaneous arteries removed in association with abdominal surgery. 2 BIBN4096BS, at the concentration of 1 pM, had no significant effect on the CGRP-induced relaxation in these vessels. 3 At the concentration of 10 pM, BIBN4096BS had a competitive antagonistic-like behaviour characterized by parallel rightward shift in the log CGRP concentration-tension curve with no depression of the E-max. 4 At the higher concentrations (0.1 and 1 nM), BIBN4096BS had a concentration-dependent noncompetitive antagonistic effect on the CGRP-induced responses. 5 The efficacy and potency of CGRP was significantly greater in the smaller ( lumen diameter similar to200 mum) human subcutaneous arteries compared to the larger ones. 6 The apparent agonist equilibrium dissociation constant, K-A, for CGRP(1) receptors in the human subcutaneous arteries was approximately 1 nM. Analysis of the relationship between receptor occupancy and response to CGRP indicates that the receptor reserve is relatively small. 7 Using reverse transcriptase-polymerase chain reaction (RT-PCR), the presence of mRNA sequences encoding the calcitonin receptor-like receptor, receptor activity modifying protein (RAMP1, RAMP2, RAMP3) and receptor component protein were demonstrated in human subcutaneous arteries, indicating the presence of CGRP1-like receptor and the necessary component for the receptor activation. 8 In conclusion, the inhibitory action of BIBN4096BS at the low concentration ( 10 pM) on the CGRP-tension curve (but not intracellular calcium concentration ([Ca2+](i)) resembles what is seen with a reversible competitive antagonist. However, at the higher concentrations ( 0.1 and 1 nM), BIBN4096BS acts as a selective noncompetitive inhibitor at CGRP1 receptors in human subcutaneous arteries

Differential localization and characterization of functional calcitonin gene-related peptide receptors in human subcutaneous arteries.

Calcitonin gene-related peptide (CGRP) and its receptor are widely distributed within the circulation and the mechanism behind its vasodilation not only differs from one animal species to another but is also dependent on the type and size of vessel. The present study examines the nature of CGRP-induced vasodilation, characteristics of the CGRP receptor antagonist telcagepant and localization of the key components calcitonin receptor-like receptor (CLR) and receptor activity modifying protein 1 (RAMP1) of the CGRP receptor in human subcutaneous arteries