Effects of two volatile anesthetics and a volatile convulsant on the excitatory and inhibitory amino acid responses in dissociated CNS neurons of the rat.
1. Effects of two volatile anesthetics [halothane (Hal) and enflurane (Enf)] and a volatile convulsant [hexafluorodiethyl ether (HFE)] on amino acid-induced membrane currents in neurons dissociated from the nucleus tractus solitarius of the rat were examined. The dissociated neurons were voltage clamped in the whole-cell mode of the patch-clamp technique. All drugs were applied with a microperfusion system, termed the "Y-tube" method. 2. The glutamate (Glu)-induced excitatory response was slightly reduced by both the anesthetics. The responses to three agonists at Glu receptor were depressed by Hal (10(-3) M) in the rank order of quisqualate greater than N-methyl-D-aspartate greater than kainate. HFE slightly increased the Glu response at a high concentration of 2 x 10(-3) M. 3. The gamma-aminobutyric acid (GABA)-induced chloride current (ICl) was enhanced by both anesthetics. The dissociation constant (Kd) for the enhancement was 2.3 x 10(-4) M for Hal and 2.1 x 10(-4) M for Enf, and the Hill coefficient was 1.6 for Hal and 1.5 for Enf. HFE depressed the GABA response with a Kd of 8.7 x 10(-5) M and a Hill coefficient of 0.84. 4. Hal (10(-3) M) and Enf (10(-3) M) decreased the Kd of the GABA concentration-response curve from 3.5 x 10(-6) to 10(-6) and 1.9 x 10(-6) M, respectively, without changing the maximum response or the Hill coefficient (1.5). In the presence of HFE (10(-4) M), the Kd was increased to 1.4 x 10(-5) M and the Hill coefficient was slightly changed to 1.2.(ABSTRACT TRUNCATED AT 250 WORDS)
Wakamori
M
M
Department of Neurophysiology, Tohoku University School of Medicine, Sendai, Japan.
Ikemoto
Y
Y
Akaike
N
N
D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D001933:Brain Stem / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology / Q000379:methods; D004737:Enflurane / Q000494:pharmacology*; D005481:Flurothyl / Q000494:pharmacology*; D005971:Glutamates / Q000494:pharmacology; D005998:Glycine / Q000494:pharmacology; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D007608:Kainic Acid / Q000494:pharmacology; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D016318:Quisqualic Acid / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D000596:Amino Acids; D005971:Glutamates; D011963:Receptors, GABA-A; D017981:Receptors, Neurotransmitter; C030975:barbiturate receptor; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D016318:Quisqualic Acid; D004737:Enflurane; D005481:Flurothyl; D007608:Kainic Acid; D005998:Glycine; D006221:Halothane