An Improved Method for In Situ Freezing of Cat Brain for Metabolic Studies

This study introduces a new method for rapid freezing of the cat brain. The method employed a Styrofoam box which was fitted around the head of the animal. Liquid nitrogen was poured into the box until the head was submerged. Temperature changes in three brain sites (ventral hypothalamus, the fourth ventricle, and the corpus callosum) and levels of labile carbohydrate metabolites (glycogen, glucose, ATP, P-creatine, and lactate) in five brain regions (cortex, thalamus, midbrain, cerebellum, and pons) frozen by the box method were compared with those frozen by a conventional cup method in which liquid nitrogen was poured into a hollow Styrofoam cup placed on top of the skull. The box method shortened the time of arrival of the freezing front and improved the freezing rate. The time required to bring the tissue to -20 degrees C was shortened, from 20 min at the ventral hypothalamus and 10-12 min at the fourth ventricle with the cup method, to less than 5 min at both sites with the box technique. Continued perfusion of brainstem prior to freezing was demonstrated. Levels of metabolites frozen by either method were similar. Lactate levels in any of the five brain regions studied by either method were not elevated, indicating no ischemic change.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glutathione and gamma-glutamyl transpeptidase in the adult female rat brain after intraventricular injection of LHRH and somatostatin

Glutathione content and glutamyl transpeptidase activity in different regions of adult female rat brain were determined at 10 and 30 min following intraventricular injection of LHRH and somatostatin. Hypothalamic glutathione levels were significantly elevated at 10 and 30 min after a single injection of a 0.1 micrograms dose of LHRH. On the contrary, glutathione levels significantly decreased in the hypothalamus, cerebral cortex and cerebellum at 10 and 30 min after 0.5 or 1 microgram dose. However, significant decrease in brain stem glutathione was evident at 30 min after 0.5 microgram and 10 min after the 1 microgram dose. Somatostatin at doses of 0.5 microgram and 1 microgram significantly decreased glutathione levels in all four brain regions both at 10 and 30 min following injection into the 3rd ventricle. Gamma-glutamyl transpeptidase activity in the hypothalamus and cerebral cortex was significantly elevated after intraventricular injection of LHRH. However, a significant increase in gamma-glutamyl transpeptidase activity in cerebellum and brain stem was seen only with 0.5 and 1 micrograms doses of LHRH. Somatostatin also significantly increased gamma-glutamyl transpeptidase activity in hypothalamus, cerebral cortex, brain stem and cerebellum. The decrease in glutathione levels with corresponding increase in gamma-glutamyl transpeptidase activity after intraventricular administration of LHRH and somatostatin suggests a possible interaction between glutathione and hypothalamic peptides.     

THE PRESENCE OF BIOLOGICALLY LABILE COMPOUNDS DURING ISCHEMIA AND THEIR RELATIONSHIP TO THE EEG IN RAT CEREBRAL CORTEX AND HYPOTHALAMUS

—Two surgical methods are described in the present paper, allowing for the approximate determination of in vivo levels of ATP, lactate, glucose, pyruvate and glycogen in anatomically uninjured cortex and hypothalamus from unanaesthetized rats. It was not possible to obtain such levels for P-creatine in the 2 mm thick samples used in the present investigation. No fundamental difference was observed between the cortical and the hypo-thalamic levels of these substrates nor in their fluxes. The substrate fluxes during ischemia were correlated with electrical activity in the rat cortex and hypothalamus, recorded by means of telemetrically transmitted electroencephalograms. The electrical activity declined precipitously at 9.6 s after decapitation in the cortex, and after 12.1 s in the hypothalamus. High levels of glycogen, glucose and ATP were present at this moment, while P-creatine had declined sharply.     

METABOLIC CHANGES IN THE BRAINS OF MICE FROZEN IN LIQUID NITROGEN

Abstract— Autolytic changes in the mouse brain, occurring during immersion of the animal in liquid nitrogen, were evaluated by measuring the tissue concentrations of glucose, lactate, pyruvate, α-oxoglutarate, phosphocreatine, creatine, ATP, ADP and AMP. The values thus obtained were compared with those obtained in paralysed mice under nitrous oxide anaesthesia, the brains of which were frozen in such a way that arterial blood pressure and oxygénation were upheld during the freezing. Immersion of unanaesthetized mice in liquid nitrogen gave rise to significant alterations in phosphocreatine, creatine, lactate, lactate/pyruvate ratio, ADP and AMP. A comparison with values obtained in paralysed and anaesthetized mice that were frozen by immersion in liquid nitrogen showed that the metabolic changes observed in the unanaesthetized animals could not be caused by an anaesthetic effect on the metabolic pattern. It is concluded that autolysis in the mouse brain occurs during immersion of the animal in a coolant, mainly because arterial hypoxia develops before the tissue is frozen. A comparison with previous results on rat cerebral cortex indicates that mice offer no advantage for studies of cerebral metabolites in unanaesthetized animals. In both species, accurate analyses of labile cerebral metabolites require that the brain is frozen in a way that prevents arterial hypoxia during the fixation of the tissue.     

Distribution of oxytocic and vasopressor activity in the rat diencephalon

The oxytocic and vasopressor activity was studied in five 1 mm thick, horizontal sections of the rat diencephalon. The diencephalon was cut frozen in dry ice. The sections obtained from identical parts of the diencephalon of 10 rats were homogenized together in 0.9% NaCl solution acidified with glacial acetic acid. The homogenate was heated to 100 degrees C for 5 min and centrifuged. The oxytocic activity of extracts was determined in vitro by, the method of Holton using the rat myometrium. The vasopressor activity was determined in vivo recording blood pressure in the carotid artery of rat by the method of Dekańaski. Oxytocic activity was found in all five sections of diencephalon and vasopressor activity in only two sections. The first section included the median eminence and ventral hypothalamus together with the supraoptic nucleus, the second section included the the dorsal hypothalamus with paraventricular nucleus, the third section--the ventral thalamus, the fourth section--the middle part of thalamus, the fifth section--the dorsal thalamus.     

THE CONVULSANT ACTION OF HYDRAZIDES AND REGIONAL CHANGES IN CEREBRAL γ-AMINOBUTYRIC ACID AND PYRIDOXAL PHOSPHATE CONCENTRATIONS

Abstract— Regional changes in the concentration of GABA and pyridoxal phosphate were determined in rat brain after i.p. administration of convulsant doses of methyldithiocarbazinate (11 mg/kg), isonicotinic acid hydrazide (250 mg/kg) and thiosemicarbazide (25 mg/kg). At 15 and 30 min after methyldithiocarbazinate GABA concentrations were reduced in all brain regions (except ventral mid-brain). After 30 min the largest decrease was in the cerebellum (41%) and the smallest decrease in the hypothalamus (20%). Pyridoxal phosphate concentrations were decreased by 39-57%. After isonicotinic acid hydrazide. the regional decreases in GABA concentration were smaller and of slower onset than those seen after methyldithiocarbazinate. The pons-medulla was the first region to show a decrease (at 15 min) whereas a decrease was not seen in the frontal cortex until 45 min. Regional decreases in pyridoxal phosphate were smaller than those seen after methyldithiocarbazinate. After thiosemicarbazide, small regional decreases in GABA concentration were observed only in the hypothalamus, cerebellum, pons-medulla and posterior cortex (13-18%) and there was no apparent correlation between regional decreases in pyridoxal phosphate and regional decreases in GABA.     

Differential distribution of the 5-alpha-reductase in the central nervous system of the rat and the mouse: are the white matter structures of the brain target tissue for testosterone action?

In the brain of several animal species testosterone is converted into a series of 5-alpha-reduced metabolites, and especially into 17-beta-hydroxy-5-alpha-androstan-3-one (DHT), by the action of the enzyme 5-alpha-reductase. The formation of DHT has never been evaluated in the white matter structures of the brain, which are composed mainly of myelinated axons. The experiments here described were performed in order to study, in the rat and the mouse, the DHT forming activity of several white matter structures, in comparison with that of the cerebral cortex and of the hypothalamus. Two sampling techniques were used in the rat: microdissection under a stereo-microscope from frozen brain sections of fragments of corpus callosum, optic chiasm and cerebral cortex; fresh tissue macrodissection of subcortical white matter, cerebral cortex and hypothalamus. Only macrodissection was used in the mice. The data show that, independently from the sampling technique used, there are considerable quantitative differences in the distribution pattern of the 5-alpha-reductase activity within different brain structures. Both in the rat and in the mouse, the enzyme appears to be present in higher concentrations in the white matter structures, than in the cerebral cortex and in the hypothalamus. The present results clearly show that the subcortical white matter and the corpus callosum are at least three times as potent as the cerebral cortex in converting testosterone into DHT. An even higher 5-alpha-reductase activity has been found in the optic chiasm. Further work is needed in order to understand the possible physiological role of DHT formation in the white matter structures.     

THE EFFECTS OF PENTOBARBITONE-SODIUM ANAESTHESIA, SHOCK AVOIDANCE CONDITIONING AND ELECTRICAL SHOCK ON ACETYLCHOLINESTERASE ACTIVITY AND PROTEIN CONTENT IN REGIONS OF THE RAT BRAIN

Abstract— Pentobarbitone sodium anaesthesia was found to produce an increase in protein content in some regions of the rat brain, i.e. posterior cortex, caudate nucleus, and a decrease in protein content in the ventral cortex.
Acetylcholinesterase expressed in terms of wet weight was found to increase in the cerebellum, medulla, and to decrease in the medial cortex, hippocampus, thalamus and caudate nucleus. The changes in activity were not explicable in terms of a direct effect of the anaesthetic on the enzyme. A decrease in protein content of rat brain was observed in the frontal cortex, ventral cortex, hippocampus and caudate nucleus after electrical shocks. Following shock avoidance conditioning procedure (shuttle-box), decreases in protein content were observed in the medial cortex, posterior cortex, cerebellum and ventral cortex; in the thalamus an increase in protein content was observed.
Changes in AChE activity were observed following footshock in the frontal cortex and medulla where there was an increase in activity and in the caudate nucleus, hypothalamus, thalamus, and olfactory tubercle where there was a decrease in activity.
Following shock avoidance conditioning the activity of the AChE increased in posterior cortex, hippocampus, thalamus and hypothalamus and the activity of the enzyme decreased in the ventral cortex.     

反复摄取烟碱对脑肌醇含量的影响

急性实验中,间隔５ｍｉｎ反复注射烟碱０．５,１．０,１．０,２．０,２．０ｍｇ／ｋｇｉｐ,３０ｍｉｎ后大鼠大脑皮层及海马中肌醇含量升高,但纹状体中肌醇含量无显著变化;相同条件下,氯化锂１０ｍｍｏｌ／ｋｇｉｐ３０ｍｉｎ后大脑皮层和海马中肌醇含量显著降低;慢性实验中,烟碱２．０－１０．０ｍｇ／ｋｇｓｃｂｉｄ１４ｄ后,大鼠大脑皮层中肌醇含量显著增高;烟碱２．６９－１１．５３ｍｇ／ｋｇ／ｄｐｏ６４ｄ后,大鼠大脑皮层中肌醇含量也显著增高。表明烟碱的作用不同于氯化锂,反复给予烟碱可使大鼠大脑皮层中肌醇含量增加。     

CEREBRAL METABOLIC CHANGES IN PROFOUND, INSULIN-INDUCED HYPOGLYCEMIA, AND IN THE RECOVERY PERIOD FOLLOWING GLUCOSE ADMINISTRATION

Severe hypoglycemia was induced by insulin in lightly anaesthetized (70°_o N₂O) and artificially ventilated rats. Brain tissue was frozen in situ after spontaneous EEG potentials had disappeared for 5. 10. 15 or 30 min and cerebral cortex concentrations of labile organic phosphates, glycolytic metabolites, ammonia and amino acids were determined. In other experiments, recovery was induced by glucose injection at the end of the period of EEG silence. All animals with an isoelectric EEG showed extensive deterioration of the cerebral energy state. and gross perturbation of amino acid concentrations. The latter included a 4-fold rise in aspartate concentration and reductions in glutamate and glutamine concentrations to 20 and 5^o_o of control levels respectively. There was an associated rise in ammonia concentration to about 3μmol-g^-1. Administration of glucose brought about extensive recovery of cerebral energy metabolism. For example, after an isoelectric period of 30 min tissue concentrations of phosphocreatine returned to or above normal, the accumulation of ADP and AMP was reversed, there was extensive resynthesis of glycogen and glutamine and full normalisation of tissue concentrations of pyruvate. α-ketoglutarate. GABA and ammonia. However, even after 3 h of recovery there was a reduction in the ATP concentration and thereby in adenine nucleotide pool, moderate elevations of lactate content and the lactate pyruvate ratio, and less than complete restoration of the amino acid pool. It is concluded that some cells may have been irreversibly damaged by the hypoglycemia.     

Acetaminophen distribution in the rat central nervous system

Based on the evidence that the antinociceptive effects of acetaminophen could be mediated centrally, tissue distribution of the drug after systemic administration was determined in rat anterior and posterior cortex, striatum, hippocampus, hypothalamus, brain stem, ventral and dorsal spinal cord. In a first study, rats were treated with acetaminophen at 100, 200 or 400 mg/kg per os (p.o.), and drug levels were determined at 15, 45, 120, 240 min by high performance liquid chromatography (HPLC) coupled with electrochemical detection (ED). In a second study, 45 min after i.v. administration of [3H]acetaminophen (43 microCi/rat; 0.65 microg/kg), radioactivity was counted in the same structures, plus the septum, the anterior raphe area and the cerebellum. Both methods showed a homogeneous distribution of acetaminophen in all structures studied. Using the HPLC-ED method, maximal distribution appeared at 45 min. Tissue concentrations of acetaminophen then decreased rapidly except at the dose of 400 mg/kg where levels were still high 240 min after administration, probably because of the saturation of clearance mechanisms. Tissue levels increased with the dose up to 200 mg/kg and then leveled off up to 400 mg/kg. Using the radioactive method, it was found that the tissue/blood ratio was remarkably constant throughout the CNS, ranking from 0.39 in the dorsal spinal cord to 0.46 in the cerebellum. These results, indicative of a massive impregnation of all brain regions, are consistent with a central antinociceptive action of acetaminophen.     

Effect of beta-endorphin on catecholamine levels in the rat hypothalamus and cerebral cortex

The present paper deals with the effect of beta-endorphin on catecholamine content in the hypothalamus and cerebral cortex of male rats. beta-endorphin was found to decrease catecholamine content in the rat brain, with the degree of reduction depending on the brain topography and the time following the peptide administration. 5 min later no changes in catecholamine content were observed either in the hypothalamus or in the cerebral cortex. 20 min later beta-endorphin induced a statistically significant fall of catecholamine concentration in the hypothalamus. A tendency towards its decrease was also observed in the cerebral cortex. 60 min later beta-endorphin produced an insignificant decrease in catecholamine level in both brain areas under study. It may be therefore suggested that beta-endorphin-induced decrease of catecholamine content in the hypothalamus and cerebral cortex represents one of the mechanisms underlying beta-endorphin stimulating action on a number of trophic functions of the hypophysis.     

IN VIVO EFFECTS OF AMPHETAMINE ON METABOLITES AND METABOLIC RATE IN BRAIN

—The concentrations of several metabolites, including glucose, glycogen, glucose-6-phosphate, lactate, ATP and phosphocreatine have been measured in the brains of mice rapidly frozen at various intervals after the intraperitoneal injection of d -amphetamine sulphate (5 mg/kg). During the initial 30 min following injection, amphetamine induced a fall in cerebral glycogen and phosphocreatine and an elevation of lactate. Changes in glucose and brain/blood glucose ratios were less marked over this period. The metabolite levels returned to control values at 60 min. The cerebral metabolic rate calculated by the ‘closed system’ technique also showed a biphasic change. An initial depression of energy flux over the first 15 min following amphetamine injection was followed by an increase that appeared to be closely associated with the increase in locomotor activity over this period. The results have been discussed in relation to the known catecholamine-releasing action of amphetamine, and differential effects on glial cells and neurons have been proposed.     

Regional distribution and relative amounts of glutamate decarboxylase isoforms in rat and mouse brain.

The levels of the two isoforms of glutamate decarboxylase (GAD) were measured in 12 regions of adult rat brain and three regions of mouse brain by sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblotting with an antiserum that recognizes the identical C-terminal sequence in both isoforms from both species. In rat brain the amount of smaller isoform, GAD65, was greater than that of the larger isoform, GAD67, in all twelve regions. GAD65 ranged from 77-89% of total GAD in frontal cortex, hippocampus, hypothalamus, midbrain, olfactory bulb, periaqueductal gray matter, substantia nigra, striatum, thalamus and the ventral tegmental area. The proportion of GAD65 was lower in amygdala and cerebellum but still greater than half of the total. There was a strong correlation between total GAD protein and GAD activity. In the three mouse brain regions analysed (cerebellum, cerebral cortex and hippocampus) the proportion of GAD65 (35,47, and 51% of total GAD) was significantly lower than in the corresponding rat-brain regions. The amount of GAD67 was greater than the amount of GAD65 in mouse cerebellum and was approximately equal to the amount of GAD65 in mouse cerebral cortex and hippocampus.     

DNA microarray unravels rapid changes in transcriptome of MK-801 treated rat brain

AIM:To investigate the impact of MK-801 on gene expression patterns genome wide in rat brain regions. METHODS:Rats were treated with an intraperitoneal injection of MK-801 [0.08(low-dose) and 0.16(highdose) mg/kg] or NaC l(vehicle control). In a first series of experiment,the frontoparietal electrocorticogram was recorded 15 min before and 60 min after injection. In a second series of experiments,the whole brain of each animal was rapidly removed at 40 min post-injection,and different regions were separated:amygdala,cerebral cortex,hippocampus,hypothalamus,midbrain and ventral striatum on ice followed by DNA microarray(4 × 44 K whole rat genome chip) analysis.RESULTS:Spectral analysis revealed that a single systemic injection of MK-801 significantly and selectively augmented the power of baseline gamma frequency(30-80 Hz) oscillations in the frontoparietal electroencephalogram. DNA microarray analysis showed the largest number(up- and down- regulations) of gene expressions in the cerebral cortex(378),midbrain(376),hippocampus(375),ventral striatum(353),amygdala(301),and hypothalamus(201) under low-dose(0.08 mg/kg) of MK-801. Under high-dose(0.16 mg/kg),ventral striatum(811) showed the largest number of gene expression changes. Gene expression changes were functionally categorized to reveal expression of genes and function varies with each brain region.CONCLUSION:Acute MK-801 treatment increases synchrony of baseline gamma oscillations,and causes very early changes in gene expressions in six individual rat brain regions,a first report.     

EFFECTS OF GAMMA-HYDROXYBUTYRIC ACID AND OTHER HYPNOTICS ON GLUCOSE UPTAKE IN VIVO AND IN VITRO

Abstract— (1) The effects of gamma-hydroxybutyrate, imidazole-4-acetic acid and pento-barbitone on mouse brain glucose, glycogen and lactate levels have been studied. All the drugs significantly increased the brain glucose content, but did not significantly alter brain glycogen levels. The increase in brain glucose following imidazole-4-acetic acid or hypnotic doses of pentobarbitone was matched by corresponding decreases in the lactate level; this was not the case with gamma-hydroxybutyrate where the total glucose equivalents in the brain, expressed as the tissue level of (glucose) + (lactate/2), were significantly increased.
(2) All drugs except imidazole-4-acetic acid significantly decreased the rate of appearance of [¹⁴C]glucose into the bloodstream in vivo but had no effect on the uptake of glucose into rat diaphragm in vitro when present at 2·5 mM concentration.
(3) Only imidazole-4-acetic acid significantly inhibited glucose uptake into the brain in vivo but at 2·5 mM had no significant effect on glucose uptake into rat cerebral cortical slices in vitro.
(4) It is concluded that the very large increase in brain glucose level observed following the injection of hypnotic doses of gamma-hydroxybutyrate cannot be explained in terms of an increased net uptake of glucose into the brain.     

INCORPORATION OF 14C FROM [U-14C]GLUCOSE INTO FREE AMINO ACIDS IN MOUSE BRAIN LOCI IN VIVO UNDER NORMAL CONDITIONS

By macroautoradiography and by GLC separation, differences in the uptake of radioactive carbon from [U-¹⁴C]glucose into free amino acids (glutamate + glutamine, aspartate + asparagine, GABA, alanine and glycine) in mouse cerebral neocortex, hippocampus, thalamus and hypothalamus were investigated. (1) The autoradiographical densities in the thalamus, cerebral neocortex and hippocampus measured with a microdensitometer were higher than that in the hypothalamus at 5 min after subcutaneous injection. At 180 min, densities in the cerebral neocortex, hippocampus and hypothalamus were higher than that in thalamus. (2) The free amino acid levels determined by GLC varied with each brain region. (3) The specific radioactivity (d.p.m./μmol) of alanine in each brain region was higher than that of the other amino acids at 5 min after the injection. The specific radioactivity of GABA in the brain regions was clearly higher than that of (glutamate + glutamine), (aspartate + asparagine) and glycine at 5 and 15 min. (4) The autoradiographical data were in good agreement with the chemical data at 5 min but were different at 180 min. (5) Variations in specific radioactivity of each free amino acid among brain regions at 5 min were influenced greatly by existing free amino acid concentrations in each region.     

OPTIMAL FREEZING CONDITIONS FOR CEREBRAL METABOLITES IN RATS

Abstract— Optimal freezing conditions for metabolites were evaluated in 250-450 g rats. As a standard procedure, the brains were frozen in such a way that the blood pressure and arterial oxygenation were upheld during the freezing. The progression of the freezing front was determined by means of implanted thermocouples, and the interruption of the circulation by means of injections of carbon particles into the blood stream. The freezing gave rise to a rapid interruption of the circulation in the superficial cortical layer first reached by the freezing front well before the temperature reached 0°C. In deeper regions the progression of the freezing front was slower and interruption of the circulation occurred simultaneously with the freezing of the tissue. Measurements of labile cerebral metabolites, including phosphocreatine, ATP, ADP, AMP and lactate, failed to show signs of autolysis in the part of cortex which became unperfused at temperatures above zero. Since the energy state was identical in superficial cortical areas and in areas that did not freeze until after 40–90 s, it is concluded that the freezing technique gives optimal conditions for metabolites also in deep cerebral structures. Decapitation of unanaesthetized animals gave rise to large autolytic changes in the cerebral cortex. In unanaesthetized animals that were immersed in liquid nitrogen the changes were less marked and mainly affected the concentrations of phosphocreatine, ADP and lactate. When paralysed animals that were anaesthetized with N₂O were immersed in liquid nitrogen the only significant change from the control was a decrease in phosphocreatine content. The virtual absence of autolytic changes in this group of animals was not related to the anaesthesia since more pronounced changes were observed in phenobarbitone-anaesthetized rats immersed in the coolant. These differences could be explained by the fact that spontaneously breathing animals immersed in liquid nitrogen developed arterial hypoxia much faster than paralysed animals. It is concluded that an optimal metabolite pattern can only be obtained in anaesthetized animals, frozen with a method that was described by Kerr almost 40 years ago (Kerr , 1935). If unanaesthetized animals must be used, greater attention should be paid to the oxygenation of the blood during the freezing than to such factors as speed of freezing or depth of anaesthesia.     

GLYCOGEN AND GLYCOGEN PHOSPHORYLASE IN THE CEREBRAL CORTEX OF MICE UNDER THE INFLUENCE OF METHIONINE SULPHOXIMINE

Abstract— Glucose and glycogen levels in the mouse cerebral cortex in vivo were studied after recovery from methionine sulphoximine seizures. The animals appeared normal 24 h after methionine sulphoximine administration but both glucose and glycogen still persisted at higher levels 72 h after injection (by 64 and 275 per cent, respectively). When seizures were prevented by methionine, the increase in glucose and glycogen at the longer time intervals was significantly smaller than in animals treated with methionine sulphoximine only; glucose reached normal values at 48 or 72 h; the accumulation of glycogen was reduced by about three to five times, but after 72 h the levels were still significantly higher than in control animals (67 or 32 per cent increase, depending on the administered dose of methionine). In contrast to the considerable accumulation of glycogen after administration of methionine sulphoximine in vivo, it had no effect on the level of glycogen in brain cortex slices in vitro. After 3 h incubation in the absence of methionine sulphoximine, glycogen was resynthesized to a level of about 4 μmol/g wet tissue and this value was not significantly affected by the presence of various concentrations of methionine sulphoximine in the incubation medium (10^-5 to 10^-2 M). The total (a+b forms) phosphorylase activity of mouse cerebral cortex in vivo after methionine sulphoximine administration was not affected. The fraction of active phosphorylase was reduced by about 50 per cent at the time of seizures. When seizures were prevented by methionine, the decrease in active phosphorylase was also completely prevented. In the preconvulsive period (1-2 h) and after recovery from the seizures (48 h after methionine sulphoximine administration) active phosphorylase was normal. The possible mechanisms involved in the increased accumulation of glycogen after methionine sulphoximine administration are discussed.