Mechanism of stimulation of cyclic-GMP level in a neuronal cell line mediated by serotonin (5-HT3) receptors. Involvement of nitric oxide, arachidonic-acid metabolism and cytosolic Ca2+.
The mechanism by which serotonin (5-HT3) receptors mediate a rise in cyclic-GMP level was investigated in a neuronal cell line. Inhibitors of phospholipase A2 (mepacrine) and of lipoxygenase (eicosatetraynoic acid or nordihydroguaiaretic acid) suppressed the action of serotonin. On the other hand, inhibition by hemoglobin indicates a role for nitric oxide which could be in part responsible for the cyclic-GMP effect as an intercellular stimulant. The suppression of the serotonin effect by the arginine analogues N omega-methyl-L-arginine and canavanine is consistent with the notion that nitric oxide could be released from arginine. The serotonin-induced rise of cyclic-GMP level depends on the presence of extracellular Ca2+ with half-maximal stimulation at 0.3 mM Ca2+. The serotonin-stimulated rise of cyclic GMP was inhibited by (a) addition of inorganic blockers of Ca2(+)-permeable channels (La3+, half-maximal inhibitory concentration (IC50) 0.04 mM; Mn2+, IC50, 0.4 mM; Co2+, IC50, 0.9 mM; Ni2+, IC50, 1.2 mM) and (b) of organic blockers (diltiazem: IC50, 6 microM, methoxyverapamil: IC50, 3 microM and (c) intracellular application of the Ca2+ chelator bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (IC50, 2 microM). Thus, two pathways for the activation of soluble guanylate cyclase by serotonin are possible: (a) via lipoxygenase products of arachidonic acid and/or (b) via nitric oxide or a related nitroso compound. Serotonin mediates a rise of cytosolic Ca2+ activity due to entry of extracellular Ca2+. It still has to be investigated which step depends on a rise of cytosolic Ca2+ activity that appears to be a prerequisite for activation of guanylate cyclase.
Reiser
G
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Physiologisch-chemisches Institut, Universität Tübingen, Federal Republic of Germany.
D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D001120:Arginine / Q000031:analogs & derivatives; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D006152:Cyclic GMP / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D006454:Hemoglobins / Q000494:pharmacology; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology
D001095:Arachidonic Acids; D002121:Calcium Channel Blockers; D006454:Hemoglobins; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D016718:Arachidonic Acid; D009569:Nitric Oxide; D012701:Serotonin; D001120:Arginine; D006152:Cyclic GMP; D001920:Bradykinin; D002118:Calcium