Atsushi Asanuma

Taurine and β-alanine act on both GABA and glycine receptors in Xenopus oocyte injected with mouse brain messenger RNA

The responding pathway (process from agonist binding to channel opening) of taurine and beta-alanine was investigated in Xenopus oocytes injected with mouse brain poly(A)+ RNA. Responses to gamma-aminobutyric acid (GABA), glycine, taurine and beta-alanine were induced in oocytes injected with poly(A)+ RNA extracted from 3 regions, cerebrum, cerebellum and brainstem of the mouse brain. From comparison, responses to these 4 inhibitory amino acids in each regional poly(A)+ RNA-injected oocytes were categorized into at least 3 groups: (1) GABA, (2) glycine, and (3) taurine and beta-alanine. No cross-desensitization was observed between GABA response and glycine response, but taurine and beta-alanine responses cross-desensitized both the GABA and glycine responses. Taurine and beta-alanine responses were partially inhibited by the GABA antagonist, bicuculline, and also by the glycine antagonist, strychnine. The results suggest that the taurine or the beta-alanine response in the brain is caused through both the GABA receptor and the glycine receptor.

Regional distribution of metabotropic glutamate response in the rat brain using Xenopus oocytes

The regional distribution of metabotropic L-glutamate responses was investigated in Xenopus oocytes injected with poly(A)+-RNA from a rat brain which was separated into 3 parts: cerebrum, cerebellum and brainstem. Under voltage-clamp, oscillatory current responses were induced more in cerebellum or brainstem poly (A)+-RNA-injected oocytes, and less in cerebrum poly(A)+-RNA-injected oocytes. These results suggest that the metabotropic glutamate receptor is distributed mostly in cerebellum and brainstem.

The distribution of GABA and glycine response in the mouse brain using Xenopus oocytes.

Injection of mRNA from different regions of the central nervous system (CNS) of the mouse into the Xenopus oocyte caused a difference in the relative glycine to gamma-aminobutyric acid (GABA) response of the oocyte. Glycine caused the response in oocytes injected with brainstem mRNA but hardly in oocytes injected with cerebrum mRNA and in oocytes injected with cerebellum mRNA. In contrast, GABA caused the response in oocytes injected with mRNA from each of the 3 parts of the CNS. These obvious regional differences may reflect the distribution of the receptors to each plausible neurotransmitter in the CNS.

Induction of taurine responsiveness in Xenopus oocytes by messenger RNA from mouse brain

A taurine response was induced in the surface membrane of the oocytes of Xenopus laevis by injection of the mRNA from the neonatal mouse brain, and the response was studied electrophysiologically. The permeability of mRNA-injected oocytes to chloride ions was increased by the application of taurine in a dose-dependent manner. The same oocyte also responded to GABA, but bicuculline suppressed only the GABA response. These results suggest a possibility that taurine could be a neurotransmitter of certain neurons as yet unknown in the central nervous system.

Reversible suppression of action potentials of Xenopus tactile nerve fibers to Nd:YAG laser irradiation with and without Chinese ink

Abstract We have reported that pain could be effectively relieved by Nd:YAG laser irradiation in dental or periodontal treatment, and that painting Chinese ink on the mucogingival surface reinforces the efficacy of anesthesia with laser irradiation. However, the effect of Chinese ink on nerve action potentials (a.p.) in this pain relief is not clear. In this study Xenopus tactile nerve fibers were used to clarify this efficacy. Dorsal surface skin was removed with fine tactile nerve bundles, and was put on the filter paper absorbed physiological buffer solution, and fastened on the rubber mat. From a bundle, a.p. with tactile stimuli on the skin surface were recorded by a silver electrode, and counted by the spike counter. After noncontact Nd:YAG laser irradiation (15 pps, 100 mJ, 60 s), with or without Chinese ink painting, tactile responses were periodically recorded. Results were as follows: (1) The conduction of a.p. was reversibly suppressed in the bundle; (2) Chinese ink painting has a considerable effect on reversible suppression; and (3) the suppressive effect was not certain in nerve bundles without Chinese ink painting. These results endorse that Chinese ink painting is effective for patients on dental or periodontal pain control using laser irradiation.

Taurine modulates glycine response in Xenopus oocytes injected with messenger RNA from mouse brain

The modulatory action of taurine on the glycine response was investigated in Xenopus oocytes injected with messenger RNA from mouse brainstem under voltage-clamped condition. Taurine competitively inhibited the glycine response in a dose-dependent manner. This inhibition was insensitive to bicuculline and intracellularly injected EGTA. The results suggest that taurine could directly modulate glycinergic neurotransmission in the central nervous system.