Masao Kozuka

Changes in holding and ion‐channel currents during activation of an ascidian egg under voltage clamp

1. The unfertilized egg of an ascidian, Halocynthia roretzi, was activated by the divalent ionophore A23187 in natural or artificial sea water (nSW or ASW) or by an external solution containing a high concentration of Ca ions (high‐Ca ASW) under voltage‐clamp condition.

Changes in levels of monoamines and their metabolites in incompletely ischemic brains of spontaneously hypertensive rats

In order to investigate changes in levels of monoamines and their related substances together with those of other neurotransmitters (acetylcholine and GABA), choline and substances related to energy metabolism (ATP, lactate and glucose) accompanying incomplete cerebral ischemia, a bilateral common carotid artery occlusion model of spontaneously hypertensive rats (SHR) was utilized. Animals were subjected to 1 or 2 h ischemia. Then the concentrations of substances were measured in the cerebral cortex, hippocampus and striatum and compared with control values. Due to the incomplete ischemia, ATP showed a moderate decrease, while lactate and choline increased remarkably, and GABA underwent a moderate increase. With regard to monoamines, both noradrenaline and serotonin levels were reduced in the cerebral cortex and hippocampus, whereas dopamine levels increased in the hippocampus. All monoamine metabolites, i.e. metabolites by monoamine oxidase (MAO), metabolites by catechol-O-methyltransferase (COMT), and metabolites by both MAO and COMT, underwent increases. The 3-methoxytyramine level in particular showed marked increases. Furthermore levels of precursor amino acids as well as 5-hydroxytryptophan rose. Acetylcholine decreased moderately only in the cerebral cortex. Among these changes, sustained increases in all the monoamine metabolites were characteristic in the incompletely ischemic brain, suggesting that both COMT and MAO retain their activities in the incompletely ischemic brain.

Changes in Brain Energy Metabolism, Neurotransmitters, and Choline During and After Incomplete Cerebral Ischemia in Spontaneously Hypertensive Rats

In order to investigate changes in energy metabolism, neurotransmitters, and membrane disorder accompanying incomplete cerebral ischemia, a bilateral common carotid artery occlusion model of spontaneously hypertensive rats was utilized. We measured concentrations of ATP, phosphocreatine (PCr), lactate (Lac), glucose (Glu), acetylcholine (ACh), choline (Ch), and γ-aminobutyric acid (GABA) in both the cerebral cortex and the subcortical regions after 1 h ischemia, 2 h ischemia, and 2 h reflow following 2 h ischemia, and then examined changes in concentrations of these substances during and after incomplete cerebral ischemia. Also examined were interrelations of changes in these substance levels during ischemia. In the cerebral cortex, levels of ATP, PCr, Glu, and ACh decreased, and levels of Lac, Ch, and GABA increased during ischemia. After recirculation, levels of ATP, PCr, Ch, and GABA tended to return to the normal range. On the other hand, the Lac level remained in the ischemic range and the Glu level rose and greatly exceeded the normal range. With regard to ACh, most animals showed normal levels but some exceeded the normal range. Changes in the subcortical regions were qualitatively the same as those in the cerebral cortex during and after ischemia (except with Glu), but only smaller in degrees. Glu levels remained unchanged during ischemia. Correlation of the levels of these substances in the cerebral cortex was examined using normal and ischemic values. A high correlation was generally observed between ATP and other substance levels. The relations between ATP and either PCr or Glu levels were linear. The relation between ATP and ACh levels was logarithmic. The relations between ATP and either Lac, Ch, or GABA levels were exponential. Namely, ACh, Lac, Ch, and GABA levels stayed constant until ATP fell to some fixed low level, suggesting the existence of a threshold. High correlations were also observed among Lac, Ch, and GABA levels.

Pharmacological profiles of CS-932, a functionally selective M1 agonist

NOBUYUKI KaSAWAl, KAZUKO WATANABE2, YOKO YAMAWAKI’, IKUKO NAGATSU ‘AND MINORU ONOZUKA3 lDept. of gnat., Fujita Health Univ. Sch. of Med., Toyoake. 470-l 101, Japan; Depts. of 2Physiology and 3Anat., Gifu Univ. Sch of Med., Gifi.r 500-8076, Japan To analyze age-associated changes in monoamine-biosynthesizing ability, we studied senescence-accelerated mice (SAM-P/& 8 months old) and accelerated senescence-resistant mice (SAM-R/l,8 months old) as controls. We administered, intraperitoneahy, 2, 4-diamino-&hydroxypyrimidine (DAHP) or parachlorophenylalanine (PCPA) to both groups of mice and measured the time course of changes in dopamine (DA)immunoreactivity (IR) in the nigrostriatal system, and serotonm (5-HT)IR in the raphe dorsalis in PAP-stained sections using a microphotometry system (Luzex FS, Nicon). While DA-IR in the nigrostriatal system of SAM-R/l was lowest at 3 h after the administration of DAHP and recovered to normal value 24 h after, that of the SAM-p/8 was lowest at 6 h following DAHP administration and did not recover even after 72 h. With respect to 5-HT-IR, while that in SAM-R/l following PCPA administration was lowest at 24 h after the administrauon and recovered 48-72 h after, that in SAM-P/8 showed almost no change at 24 h after and decreased slightly 48-72 h after the administrationThese studies strongly suggest that in SAM-P&while catecholaminergic neurons are significantly affected by monoamine synthesis inhibitors,serotonergic neurons do not show significant changes.

M1 agonist CS-932 ameliorates learning deficits in experimental models

Activation of brain functions by a functionally relative Ml agonist, CS-932, were examined in several models. CS-933 concentration-dependently increased firing rate of the cholinoceptive neurons in the rat hippocampal slices. The effect of CS932 was antagonized by the Ml antagonist, pirenzepine, but not by the M2 antagonist, AF-DX116. Cortical cholinoceptive neurons of rats, whose firing rates were increased by carbachol applied iontophoretically, were activated when the compound was intraducdenally administered. CS-932 re-sychronized the hippocampal EEG and increased the theta wave power in the rat denervated in the septohippocampal pathway. The compound antagonized scopolamine-induced slow wave EEG in rats. Under light anesthesia with pentobarbital, cortical EEG of cynomologus monkey consisted mainly of slow waves. CS-932, injected subcutaneously, dose-dependently activated the cerebral function which waas indicated by a decrease in delta waves and an increase in alpha and beta waves. These findings suggest that CS-932 can activate CSN neurons via an Ml receptor stimulation and counteract cholinergic deficits in the CNS.