Abstract
We replaced the coding region of the murine 5-hydroxytryptamine (5-HT)1B receptor by the human 5-HT1B receptor using homologous recombination in embryonic stem cells and generated and characterized homozygous transgenic mice that express only the human (h) 5-HT1B receptor. The distribution patterns of h5-HT1B and murine (m) 5-HT1B receptor mRNA and binding sites in brain sections of transgenic and wild-type mice were identical as measured by in situ hybridization histochemistry and radioligand receptor autoradiography. When measured in parallel under identical conditions, the h5-HT1B receptor expressed in mouse brain had the same pharmacological characteristics as that in human brain. Stimulation by 5-HT1B agonists of [35S]guanosine-5′-O-(3-thio)triphosphate binding in brain sections demonstrated the functional coupling of the h5-HT1B receptor to G proteins in mouse brain. In tissue slices from various brain regions, electrically stimulated [3H]5-HT release was not modified by 5-HT1Bagonists in tissue from either transgenic and wild-type mice; a 5-HT1B antagonist enhanced electrically stimulated [3H]5-HT release in wild-type mouse brain, but was ineffective in the transgenics. The centrally active 5-HT1A/5-HT1B agonist RU24969 induced hypothermia but did not increase locomotor activity in the transgenic mice. The ineffectiveness of RU24969 in the transgenic mice could be due to the lower affinity of the compound for the h5-HT1Breceptor compared with the m5-HT1B receptor. The present study demonstrates a complete replacement of the mouse receptor by its human receptor homolog and a functional coupling to G proteins. However, modulation of [3H]5-HT release could not be shown. Furthermore, behavioral effects were not clearly observed, which may be due to a lack of appropriate tools.
Footnotes
- Received January 26, 1999.
- Accepted March 21, 1999.
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Send reprint requests to: Dr. Pascal Bonaventure, R.W. Johnson Pharmaceutical Research Institute, 3535 General Atomic Court, Suite 100, San Diego, CA. E-mail: pbonave1{at}prius.jnj.com
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↵1 These two authors contributed equally to this work.
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↵2 Current address: R. W. Johnson Pharmaceutical Research Institute, 3535 General Atomic Court, Suite 100, San Diego, CA 92122.
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The experimental Genetics Group, Centrum voor Menselijke Erfelijkheid, Vlaams Interuniversitair Instituut voor Biotechnologie, Katholieke Universiteit Leuven was supported by grants from FWO-Vlaanderen, the Interuniversity Attraction Pole program (IUAP) of the Belgian government, and the Biotechnology Program of the Flemish government (IWT/VLAB/COT-008). L.U. was a postdoctoral research fellow of the Katholieke Universiteit Leuven Research Fund.
- The American Society for Pharmacology and Experimental Therapeutics
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Humanization of Mouse 5-Hydroxytryptamine1B Receptor Gene by Homologous Recombination: In Vitro and In Vivo Characterization
