Cholinergic-induced [3H] noradrenaline release in rat brain cortical slices is mediated via a pertussis toxin sensitive GTP binding protein and involves activation of protein kinase C.
The involvement of a GTP-binding protein (G-protein) in the process of neurotransmitter release was examined using pertussis toxin and cholera toxin. Cholinergic agonists are shown to mediate [3H]noradrenaline release in rat brain slices via a pertussis toxin (1.2 micrograms/ml) sensitive, and cholera toxin (0.5 microgram/ml) insensitive G-protein. An indication for the involvement of a G-protein and phospholipase C activation in the release process was implied from the inhibitory effect of neomycin on K+-, veratridine- and carbachol-induced-norepinephrine release. Depolarizing agents mediate a neomycin-sensitive release, which is not which is not affected either by pertussis toxin or cholera toxin, suggesting a different mode of phospholipase C activation, unlike carbachol-induced release, which is both neomycin and pertussis toxin sensitive. Similarly, a hormone-sensitive carrier activated by phenylephrine not via alpha 1-adrenergic receptors, mediates a non-exocytosis efflux which is not affected by neomycin and is shown to be pertussis toxin-insensitive. The inhibitory action of protein kinase C inhibitors polymyxin B, K252a and H-7 [(1-(5-isoquinolinesulphonyl)-2-methyl-piperazine] on release, strongly suggests its participation in the process. Polymyxin B, a relatively selective protein kinase C inhibitor, inhibited carbachol-induced release (IC50 = 0.53 microM) as well as the K+ and the veratridine induced [3H] noradrenaline release, K252a, an inhibitor of various protein kinases at the ATP site, and H-7, another protein kinase C inhibitor, inhibited carbachol-induced noradrenaline released with IC50 = 35 nM and 3 microM respectively. Consistent with its inability to activate phospholipase C, phenylephrine-induced noradrenaline efflux was unaffected by polymyxin B (greater than 70 microM). These results offer more supportive evidence for a major role played by the dual messengers inositol trisphosphate and diacylglycerol (IP3/DG) in the mechanisms of neuronal release.
Ari
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Department of Biological Chemistry, Hebrew University of Jerusalem, Israel.
Schwarz
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Atlas
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D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D002540:Cerebral Cortex / Q000378:metabolism*; D002772:Cholera Toxin / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D066298:In Vitro Techniques; D026121:Indole Alkaloids; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D009489:Neurosecretion / Q000187:drug effects; D009638:Norepinephrine / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D037342:Pertussis Toxin; D010656:Phenylephrine / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011112:Polymyxin B / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D014701:Veratridine / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D002227:Carbazoles; D026121:Indole Alkaloids; D007546:Isoquinolines; D010879:Piperazines; D010566:Virulence Factors, Bordetella; D010656:Phenylephrine; D010042:Ouabain; D011189:Potassium Chloride; D014701:Veratridine; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D002217:Carbachol; D002772:Cholera Toxin; C049985:staurosporine aglycone; D037342:Pertussis Toxin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D011112:Polymyxin B; D000109:Acetylcholine; D009638:Norepinephrine