Activation of multiple intracellular transduction signals by vasopressin in vasopressin-sensitive neurones of the rat supraoptic nucleus.
1. The intracellular mechanisms activated by the binding of vasopressin to its receptor(s) and which result in the increase of [Ca2+]i were investigated in freshly dissociated supraoptic nucleus neurones. Various pharmacological agents were used to investigate the possible involvement of phospholipase C (PLC) and adenylate cyclase (AC) intracellular pathways in the transduction of the vasopressin action. 2. Both the PLC inhibitor U-73122 and the protein kinase C (PKC) inhibitor calphostin C, reduced the [Ca2+]i rise elicited by vasopressin. The cAMP analogue, 8-Br-cAMP produced an increase in [Ca2+]i and IBMX, a phosphodiesterase inhibitor, potentiated the response to vasopressin. 3. After pre-incubation with the AC inhibitor SQ-22536, 7 out of 18 vasopressin-sensitive neurones showed no inhibition of the vasopressin response, while the response to vasopressin was reduced by greater than 35 % in each of the other 11 neurones. 4. The activation of protein kinase A (PKA) with Sp-cAMPS caused an increase in [Ca2+]i which was additive to the vasopressin-elicited [Ca2+]i increase. After incubation with the PKA inhibitors Rp-cAMPS or H-89, the [Ca2+]i responses triggered by Sp-cAMPS and vasopressin were, respectively, abolished and greatly reduced. 5. A combined administration of SQ-22536 (AC inhibitor) followed by U-73122 (PLC inhibitor), or U-73122 followed by H-89 (PKA inhibitor), virtually abolished the response to vasopressin. 6. In vasopressin-responsive neurones, the pituitary adenylate cyclase-activating polypeptide (PACAP) induced a [Ca2+]i increase similar to the response to vasopressin and in both cases the increase was inhibited to the same extent by a combination of U-73122 and Rp-cAMPS. 7. In conclusion, we suggest that the autoregulation exerted specifically by vasopressin on vasopressin-sensitive neurones involves the activation of both PLC- and AC-linked pathways.
Sabatier
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UPR 9055-CNRS, Biologie des Neurones Endocrines, CCIPE, 141 rue de la Cardonille, F-34094 Montpellier cedex 5,, France.
Richard
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Dayanithi
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D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004963:Estrenes / Q000494:pharmacology; D008297:Male; D009434:Neural Pathways / Q000378:metabolism / Q000502:physiology; D009474:Neurons / Q000187:drug effects*; D009479:Neuropeptides / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects*; D013268:Stimulation, Chemical; D013495:Supraoptic Nucleus / Q000166:cytology / Q000187:drug effects*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism; D014667:Vasopressins / Q000494:pharmacology*
C495403:Adcyap1 protein, rat; D000067956:Adenylyl Cyclase Inhibitors; D004963:Estrenes; D009479:Neuropeptides; D010726:Phosphodiesterase Inhibitors; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D011760:Pyrrolidinones; D014667:Vasopressins; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D010738:Type C Phospholipases; D000262:Adenylyl Cyclases