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Published December 1986 | public
Journal Article

Involvement of a GTP-binding protein in mediation of serotonin and acetylcholine responses in Xenopus oocytes injected with rat brain messenger RNA

Abstract

Injection of poly(A)⁺ RNA from rat brain into Xenopus oocytes caused the appearance of Cl currents in response to serotonin (5-HT) and acetylcholine (ACh). Both neurotransmitters evoked two-component currents similar in their time course to the oocyte's endogenous cholinergic muscarinic response, which was shown in previous studies to be mediated by IP₃ synthesis leading to Ca release from intracellular stores. The responses to ACh and 5-HT exhibited self- and cross-desensitization, i.e., application of either ACh or 5-HT inhibited the subsequent response to either one of the two transmitters. Intracellular injection of guanosine 5′-O-(3-thiotriphosphate) (GTP-γ-S) mimicked the 5-HT and ACh response, and also completely suppressed the response to the subsequent application of either ACh or 5-HT. Treatment of the oocytes with pertussis toxin (PTX) caused a 50% attenuation of ACh and 5-HT responses. In the membranes of both control and mRNA-injected oocytes, PTX catalyzed the ADP-ribosylation of a single M_r = ∼40,000 protein. Injection of the purified βγ-subunits of transducin enhanced the 5-HT response. The 5-HT and GTP-γ-S responses were inhibited by intracellular injection of the Ca²⁺ chelator, EGTA, as previously shown for the ACh response. These data suggest that ACh and 5-HT receptors, synthesized in the oocytes on the template of brain mRNA, act through a common pathway that involves (a) a guanine nucleotide binding protein and (b) IP₃ production leading to Ca mobilization.

Additional Information

© 1986 Published by Elsevier. Accepted 9 September 1986. This work was supported by NIH Grants GM-29836 to H.A.L., GM-10991 to N.D., and GM-34236 to M.S. N.D. was a recipient of Bantrell and Fulbright Postdoctoral Fellowships. H.L. was a fellow of the Deutsche Forschungsgemeinschaft. T.S. was a postdoctoral fellow of the American Heart Association/Greater Los Angeles Affiliate. The authors are grateful to Ms. Moira Fearey for excellent technical assistance.

Additional details

Created:
August 22, 2023
Modified:
October 20, 2023