Takeru Kaneko

Extracellular accumulation of glutamate in the hippocampus induced by ischemia is not calcium dependent — In vitro and in vivo evidence

Calcium dependency of ischemia-induced increase in extracellular glutamate in the hippocampus was studied in vitro and in vivo. Perfusion of a low pO2 medium without glucose (in vitro ischemia) induced an increase in extracellular glutamate in rat hippocampal slices. This increase did not depend on Ca2+, which is in contrast with the observation that about 40% of membrane depolarization (50 mM KCl)-evoked release was Ca2+-dependent. In vivo cerebral ischemia of 5 min duration in gerbils also caused Ca2+-independent increase in extracellular glutamate in the hippocampus. The data suggest that the increase in extracellular glutamate induced by ischemia is not due to the enhanced release of neurotransmitter glutamate.

Analgesic effects of dynorphin-A and morphine in mice

To investigate whether or not dynorphin-A is analgesic, the effect of this peptide was tested in comparison with that of morphine in mice. Dynorphin-A produced a potent analgesic effect in the acetic acid writhing and tail pinch tests, but a weak effect in the tail flick test when given by intracerebroventricular injection. In contrast, morphine caused a potent analgesia in all the tests. Dynorphin-A was more effective when given by intrathecal injection than by intracerebroventricular injection, whereas morphine was equipotent by both injection routes. The results suggest that dynorphin-A is analgesic and that its analgesia may be differentiated from that of morphine.

The Determination of Optical Isomers of 2-[3-(2-Chloro-Penoxyphenyl)]-Propionic Acid in Rat Plasma by High Performance Liquid Chromatography

Abstract The optical isomers of dl-2-[3-(2-chlorophenoxy-phenyl)]-propionic acid in rat plasma is converted to the diastereomeric derivatives with (+)-2-aminobutane and then determined by high performance liquid chromatography using a Nucleosil NH2 (10 μm) column and cyclohexane-ethyl acetate (5:1) as a mobile phase. The time course of the optical isomers of this drug in rat plasma after oral administration was measured. The proposed method is specific and reproducible for the determination of the optical isomers of this drug.