Inhaled Anesthetic Responses of Recombinant Receptors and Knockin Mice Harboring α2(S270H/L277A) GABAAReceptor Subunits That Are Resistant to Isoflurane
| Autor: | Irene Oh, R. A. Harris, Mandy L. McCracken, Cecilia M. Borghese, M. S. Fanselow, Edmond I. Eger, David F. Werner, J. M. Sonner, Neil L. Harrison, Sangeetha Iyer, F. Jia, Vinuta Rau, A. Swihart, Gregg E. Homanics |
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| Rok vydání: | 2010 |
| Předmět: |
Allosteric regulation
Drug Resistance Pharmacology Inhibitory postsynaptic potential Mice Xenopus laevis Neuropharmacology Conditioning Psychological medicine Animals Humans Gene Knock-In Techniques Receptor gamma-Aminobutyric Acid Isoflurane GABAA receptor Chemistry Long-term potentiation Fear Receptors GABA-A Recombinant Proteins Rats Mice Inbred C57BL Anesthetics Inhalation Anesthetic Molecular Medicine Female Righting reflex medicine.drug |
| Zdroj: | Journal of Pharmacology and Experimental Therapeutics. 336:134-144 |
| ISSN: | 1521-0103 0022-3565 |
| DOI: | 10.1124/jpet.110.170431 |
| Popis: | The mechanism by which the inhaled anesthetic isoflurane produces amnesia and immobility is not understood. Isoflurane modulates GABA(A) receptors (GABA(A)-Rs) in a manner that makes them plausible targets. We asked whether GABA(A)-R α2 subunits contribute to a site of anesthetic action in vivo. Previous studies demonstrated that Ser270 in the second transmembrane domain is involved in the modulation of GABA(A)-Rs by volatile anesthetics and alcohol, either as a binding site or a critical allosteric residue. We engineered GABA(A)-Rs with two mutations in the α2 subunit, changing Ser270 to His and Leu277 to Ala. Recombinant receptors with these mutations demonstrated normal affinity for GABA, but substantially reduced responses to isoflurane. We then produced mutant (knockin) mice in which this mutated subunit replaced the wild-type α2 subunit. The adult mutant mice were overtly normal, although there was evidence of enhanced neonatal mortality and fear conditioning. Electrophysiological recordings from dentate granule neurons in brain slices confirmed the decreased actions of isoflurane on mutant receptors contributing to inhibitory synaptic currents. The loss of righting reflex EC(50) for isoflurane did not differ between genotypes, but time to regain the righting reflex was increased in N(2) generation knockins. This effect was not observed at the N(4) generation. Isoflurane produced immobility (as measured by tail clamp) and amnesia (as measured by fear conditioning) in both wild-type and mutant mice, and potencies (EC(50)) did not differ between the strains for these actions of isoflurane. Thus, immobility or amnesia does not require isoflurane potentiation of the α2 subunit. |
| Databáze: | OpenAIRE |
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