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Chlamydomonas reinhardii cells were broken in a French press and the soluble fraction was tested for agglutination activity. Deflagellated cell bodies ofmt+ andmt- gametes yielded soluble fractions that were able to isoagglutinate gametes of the opposite mating type. When the wild-type gametes of opposite mating types were mixed, the cell body-agglutinins were used up during flagellar agglutination and subsequent cell fusion. When thefus mt+ andmt- gametes agglutinated without successive fusion, the amount of cell body-agglutinins sharply decreased, then increased and reached the premixing level: the recovery was blocked by cycloheximide. When cells were treated with EDTA or trypsin, the cell body-agglutinins as well as flagellar surface-agglutinins were completely lost without apparent loss of motility. The EDTA extract contained the same amount of agglutinins as observed in the cell bodies before extraction, and this amount was about 100 times higher than that in the EDTA extract of isolated flagella. By the addition of trypsin inhibitor, the trypsinized gametes resynthesized the cell body-agglutinins. The process was sensitive to cycloheximide in both mating type gametes and to tunicamycin inmt+ gametes.

Both crude and purified preparations of adenylosuccinate synthetase from muscle were found to combine with, and dissociate from, muscle debris precipitated from a homogenate of the muscle with water. The binding and dissociation depended on ionic strength. Further study showed that the muscle enzyme was adsorbed to F-actin, but not to G-actin or myosin. The muscle-type enzyme from the liver also associated with F-actin, but the liver-type enzyme from the liver did not. In the absence of KCl the molar ratio of adenylosuccinate synthetase from skeletal muscle to actin monomer in F-actin in the complex formed was 1 to 4. From a Scatchard plot the dissociation constant was calculated to be 0.72 micrometer. The binding was maximal at pH 5.5-7 in 30 mM potassium phosphate buffer. The complex was completely dissociated in the presence of 0.21 M KCl. The physiological significance of this binding is discussed on the basis of these findings.

Rat liver contains two types of adenylosuccinate synthetase which can be distinguished by isoelectroforcusing or immunochemical analysis. One type is identical with the enzyme in rat skeletal muscle (Type M) and the other is specific for the liver (Type L). Type L was more susceptible to nucleotide inhibition, but less susceptible to inhibition by fructose-1,6-diphosphate than Type M. These differences suggest that these isozymes play different regulatory roles in the liver.

A modified method for the determination of valproic acid, its eleven metabolites and their conjugates in small samples of serum and urine by gas chromatography—mass spectrometry with selected-ion monitoring was developed. Valproic acid and its eleven metabolites were determined in serum and urine of epileptic patients treated with valproic acid. 2-Hydroxy-2-propylpentanoic acid was identified as a new metabolite of valproic acid in the urine of 11 of the 12 patients. The unsaturated metabolites, such as (Z)- and (E-2-propyl-2-pentenoic acid, were found to be predominantly excreted as glucuronides. 3-Hydroxy-2-propylpentanoic acid and 2-propylglutaric acid were also excreted as glucuronides.

A monoclonal antibody, 1D4, recognizing a novel brain-specific protein was obtained. The 1D4 antigen is regarded to be a glycoprotein because it was adsorbed on the Con A-Sepharose column used for its purification. The antiserum (polyclonal antibodies) against the 1D4 antigen was raised in a rabbit and shown to react with just the same molecules as the 1D4 monoclonal antibody did. It was used to detect the antigen in crude tissue homogenates. The molecular mass of the 1D4 antigen was estimated to be 89 kDa by immunoblotting after sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the brain homogenate. The 1D4 antigen had multiple isoelectric points, the pattern of the bands detected on isoelectric focusing gel being quite similar to that of Type B nucleoside diphosphatase of the brain. However, they are distinct, since Type B nucleoside diphosphatase was not adsorbed by anti-1D4 antigen IgG-Sepharose 4B. The 1D4 antigen could not be detected in any of the peripheral organs or tissues tested. The 1D4 antigen was rich in the cerebrum, diencephalon, and cerebellum in the brain, and its content decreased with the distance of the region from the cerebrum. The amounts of the 1D4 antigen in the cerebrum and cerebellum increased with the respective developmental maturation. These findings suggest that the 1D4 antigen contributes to some brain-specific functions of the mature brain.

The cortico-caudate projections due to collateral axons of cortico-spinal and/or cortico-bulbar fibers were explored. In 34 cats, 59 neurons in the motor cortex were extracellularly identified to be antidromically activated by stimulation of the caudate nucleus (Cd). Thirty four neurons responded antidromically only to Cd-stimulation, and they were irresponsive to thalamic stimulation. Contrarily, 25 neurons responded antidromically not only to Cd-stimulation but also to stimulation of the cerebral peduncle and/or the medullary pyramid. 40% of the latter were orthodromically activated by thalamic stimulations. They were considered to be important in coordinating the cerebellum and the basal ganglia system.

GMP synthetase was found in the cytosolic fraction of Yoshida sarcoma ascites cells. However, prolonged centrifugation resulted in precipitation of the enzyme. On sucrose density gradient centrifugation of a crude extract of Yoshida sarcoma ascites cells, a part of this enzyme showed high sedimentability at low ionic strength. On the basis of these observations, GMP synthetase was purified from Yoshida sarcoma ascites cells by means of procedures including centrifugal fractionation. The purified enzyme was shown to be homogeneous on SDS-polyacrylamide gel electrophoresis and isoelectric focusing in polyacrylamide gel. The molecular weight of the GMP synthetase was estimated to be 78,000 by SDS-polyacrylamide gel electrophoresis and gel filtration on Sephadex G-150. Its isoelectric point was estimated to be 5.6. The Km values of this enzyme for XMP, ATP, and glutamine were calculated to be 4.6, 120, and 300 microM, respectively. Although ammonia could substitute for glutamine as a donor of the amino group, the Km value was as high as 120 mM, indicating that it cannot be considered to be a physiological substrate. This enzyme showed high activity only in the presence of Mg2+, and very low activity in the presence of other divalent cations. Inhibition by nucleoside monophosphates was not significant. The enzyme required reduced sulfhydryl compounds for its activity.

A new system is described for the classification of various types of non-mating mutants of Chlamydomonas reinhardtii. This system makes use of two simple assays: one for cell body-agglutinin (Saito et al. 1985), and another for the cell wall lytic enzyme (Matsuda et al. 1987). Both assays use the soluble fraction of homogenates from nitrogen-starved cells. Many non-mating mutants previously isolated were analysed and divided into four main phenotypic classes. This assay method is also a valuable tool for distinguishing between vegetative cells and gametes. Without this assay, verifying gametogenesis is especially difficult in agglutinin-and flagella-deficient cells. We found that wild-type cells, which had been grown for 7 days on TAP plates and lacked flagella, contain neither cell body-agglutinin activity nor lytic enzyme activity in the soluble fraction of their cell homogenates, indicating that these cells can be classified as vegetative. When suspended in nitrogen-free liquid medium, the two activities developed rapidly in parallel to the acquisition of mating ability: a maximum level was reached within two hours.

1. Dark-grown etiolated cells of Chlamydomonas reinhardtii y-1 mutant were exposed to light and the chlorophyll synthesis was examined. When the kinetics of chlorophyll synthesis were analysed in a semi-logarithmic plot, two transition points were regularly observed in the profiles. Based on these points, three phases were distinguished in the greening process: “early”, “middle”, and “late” phases. It was proposed that the three phases reflect the basic mechanism of the chloroplast development in y-1 cells. 2. Comparison of the cellular rRNA contents between y-1 cells grown in the light and in darkness revealed that there is a decrease in the amount of chloroplast rRNA in the dark-grown cells as compared to the light-grown cells, while the cytoplasmic rRNA contents remain almost the same in both cells. 3. A de novo synthesis of chloroplast rRNA to recover the amount lost in the dark occurred mainly in the “middle” phase of the greening process and was almost completed by the end of this phase.

Type B nucleoside-diphosphatase was purified from membranes of rat brain by solubilization with a non-ionic detergent and successive column chromatographies on DEAE-cellulose DE-52, concanavalin-A-Sepharose, Bio-Gel HT, blue-Sepharose CL-6B, chelating Sepharose 6B, Ultrogel AcA44 and TSK gel G3000 SW. The purified enzyme gave a single protein band on SDS/polyacrylamide gel electrophoresis and its molecular mass was estimated to be 75 kDa. It hydrolyzed thiamin diphosphate as well as GDP, IDP and UDP. Thiamin diphosphate (TPP) was hydrolyzed twice as efficiently as nucleoside diphosphates in the presence of Mn2+ at pH 7.4. The Km values for TPP, GDP, IDP and UDP were 0.66, 0.40, 0.54 and 1.06 mM respectively. ATP, ADP and pyridoxal 5'-phosphate inhibited thiamin-pyrophosphatase activity competitively and their Ki values were 2.3 mM, 1.0 mM and 0.59 mM respectively. The optimum pH of thiamin-pyrophosphatase activity was 7.4 in the presence of Mn2+ and that of GDP-hydrolytic activity was 6.5 in the presence of Mg2+.

Contraction of rat skeletal muscle by electrical stimulation of the sciatic nerve caused remarkable increase in binding of AMP deaminase (EC 3.5.4.6) to myofibrils, but did not change the total enzyme activity. After 30 sec stimulation, the ratio of bound to free enzyme was about 5 times that in resting muscle. This treatment also increased the ammonia content of the muscle to 5 times that in resting state. From these findings, we suggest that there is a correlation between the binding of muscle type AMP deaminase to myofibrils and ammoniagenesis in the muscle.

In the mouse dorsal root ganglia cultured in vitro, neurons were classified into 3 groups according to the responses of their action potentials to tetrodotoxin (TTX) and removal of Na ions from bathing medium: (1) the neurons whose action potentials were not affected by TTX by TTX (10(-6) - 10 (-5)g/ml) and which generated Ca-dependent regenerative responses under Na-free condition, (2) the neurons whose spike potentials were resistant to TTX but failed to survive in Na-free saline and (3) the neurons whose action potentials were suppressed by TTX(10(-8)g/ml) as well as Na removal. The mean duration of spike and after-hyperpolarization was longest in the first group of the neurons and shortest in the third, probably reflecting the difference in the contribution of Ca currents to action potentials. The unresponsiveness of the neurons to TTX was shown to be due to the insensitivity of Na as well as Ca components of action potentials to the toxin. It was discussed that the occurrence of TTX-resistant action potentials to the toxin. It was discussed that the occurrence of TTX-resistant action might be related to the neuronal development.

The kinetics and metabolic disposition of valproic acid following a single oral administration of two preparations of sodium valproate (sustained-release tablets, KW-6066 N ;and standard tablets, Depakene) were investigated by a Latin square cross-over method insix subjects. Determination of valproic acid and its metabolites in the serum and urinewas performed by GC/MS method.The mean elimination constants (ke), apparent volumes of distribution (Vd), areas underthe serum concentration-time curve (AUC) of the parent drug, and the sum of valproicacid and its metabolites excreted in urine showed no significant differences in the twopreparations. Therefore the extent of bioavailability of Depakene and KW-6066 N seemedto be equivalent.The pharmacokinetic parameters were estimated according to one-compartment openmodel by simultaneous least squares curve fitting method. KW-6066 N exhibited a moreprolonged absorption of valproic acid, showed a more delayed peak time (tmax), and yieldeda longer mean residence time (MRT). Maximum serum concentration (Cmax) obtained afteradministration of KW-6066 N was lower than those following the standard tablets of Depakene. These results indicate that KW-6066 N provides slow release of valproic acid.Using the pharmacokinetic parameters of valproic acid obtained in the study, serumconcentrations of valproic acid after repeated oral administration of Depakene or KW-6066N were simulated. KW-6066 N was expected to be effective even when administeredonce a day.

AMP deaminase was completely solubilized from rat skeletal muscle with 50 mM Tris-HCl buffer (pH 7.0) containing KCl at a concentration of 0.3 M or more. The purified enzyme was found to be bound to rat muscle myosin or actomyosin, but not to F-actin at KCl concentrations of less than 0.3 M. Kinetic analysis indicated that 1 mol of AMP deaminase was bound to 3 mol of myosin and that the dissociation constant ( K d ) of this binding was 0.06 μM. It was also shown that AMP deaminase from muscle interacted mainly with the light meromyosin portion of the myosin molecule. This finding differs from that of Ashby and coworkers on rabbit muscle AMP deaminase, probably due to a difference in the properties of rat and rabbit muscle AMP deaminase. AMP deaminase isozymes from rat liver, kidney and cardiac muscle did not interact with rat muscle myosin. The physiological significance of this binding of AMP deaminase to myosin is discussed.

Summary Changes in blood ammonia levels induced by intracerebral electrical stimulation were studied in rabbits with permanently implanted electrodes in the hypothalamus and the thalamus. Stimulation of the ventromedial nucleus of the hypothalamus for a period of two hours resulted in blood ammonia levels 1.5 to 2 times as high as those of the non-stimulated controls, but after a 6-hour stimulation period these levels returned to equal those of the controls, and after a 12-hour stimulation period of the same nucleus they tended to become less. Stimulation of the lateral hypothalamic area or the centre median nucleus of thalamus elicited no significant change in blood ammonia levels. The possibility that ammonia metabolism in the liver may be modified through some functional linkage between the brain and the liver was suggested.

In the previous paper (1), the author reported that the intraventricular administration of adrenaline induced both the arousal and the restng pattern of EEG in rabbits, and that the intraventricular pretreatment of alpha-adrenergic blocking agents suppressed the appearance of the resting pattern, while the resting or sleep pattern appeared more markedly following the pretreatment with beta-adrenergic blocking agents. These results suggest that the EEG resting pattern induced by the intraventricular administration of adrenaline may be dependent on its alpha action, and that there may be two contrasting effects on EEG depending on the alpha and the beta action of the catecholamine injected intraventricularly. In the present experiment, the author reevaluated these hypotheses by examining effects of the intraventricular administration of noradrenaline, phenylephrine and isoproterenol on rabbit's EEG. Modifications of the effects of intraventricularly administered adrenaline were also studied following the systemic pretreatment of dibenamine or reserpine.

Effects of quinidine (25 microM-1mM) and its stereoisomer, quinine (1-5 mM), on the excitability of CA3 pyramidal neurons were investigated in guinea-pig hippocampal slices using intracellular recording techniques. At concentrations of quinidine higher than 100 microM (and higher than 1 mM for quinine), 1) the resting potential shifted to the depolarizing direction with an increase of the input resistance, 2) the spike duration was prolonged, 3) the spike amplitude was decreased, 4) the late component of the afterhyperpolarization (AHP) (caused by the activity of the Ca2+-mediated K conductance) were suppressed, and 5) finally, neurons became inexcitable. The results indicate that the blocking action of quinidine and quinine is not specific to the Ca2+-mediated K conductance in mammalian hippocampal neurons, and that this conductance is much less sensitive to the drugs in comparison with other preparations.

Single crystals of adenylosuccinate synthetase, an essential component of purine biosynthesis, extracted from rabbit skeletal muscle were prepared as suitable specimens for X-ray structure analysis. The crystal belongs to the space group P 4 3 2 1 2 or P 4 1 2 1 2 with unit cell dimensions a = b = 71.2 A , c = 194.8 A . The asymmetric unit contains one protein molecule of 54,000 molecular weight.

The regulation of glucose transport into cultured brain cells during glucose starvation was studied. On glucose deprivation for 40 h, 2-deoxy-d-glucose (2-DG) uptake was stimulated twofold in neuronal cells but was not changed significantly in astrocytes. On refeeding, the increased activity of neuronal cells rapidly returned to the basal level, an observation indicating that the effect of glucose starvation was reversible. The increase was due solely to change in the Vmax, a finding suggesting that the number of glucose transporters on the plasma membrane is increased in starved cells. Cycloheximide inhibited this increase. In the presence of cycloheximide, the activity of 2-DG uptake of starved cells remained constant for 12 h and then slowly decreased, whereas that of fed cells decreased rapidly. These findings suggest that glucose starvation regulates glucose transport by changing the rate of net synthesis of the transporter in neuronal cells in culture.

The corticopontine projections from the paruetal association cortex (the anterior portion of the middle suprasylvian gyrus) were electrophysiologicaly investigated and compared with those form the frontal motor cortex (the anterior sigmoid gyrus) in cats under light Nembutal anaesthesia. It was indicated by field potential study that the pontine nucleus (PN) neurones receive a significant amount of the direct corticopontine fibres from both the parietal and frontal cortical areas. In extracellular unitary study, out of 107 PN neurones identified by antidromic activation due to the brachium pontis stimulation, 33 responded with firings to stimulation of the parietal association area and 64 to the frontal motor area. Only 10 of them were excited by both parietal and frontal stimulations, but they were not estimated to receive the dual monosynaptic projections from both cortical areas. There were found data suggesting that the pontocerebellar neurones with faster conduction velocities respond at shorter latencies to the cortical stimulation and those with slower conduction velocities fire at longer latencies on the cortical stimulation. No remarkable difference was observed between the topographical localization of the PN neurones receiving the projection fibres from the parietal association and the frontal motor cortical areas. It was concluded that a vast majority of the pontocerebellar neurones possibly receive monosynaptic contacts differentially with the corticopontine fibres originating from the parietal association and the frontal motor areas.

1. In lightly nembutalized cats, effects of high frequency (60–100/sec) repetitive stimulation of the midbrain reticular formation (RF) were tested upon the thalamo-cortical (T-C) neurones which project from the anterior ventral (VA) nucleus of the thalamus and its vicinities to the parietal association cortex and convey impulses responsible for cortical recruiting and spindling-like responses. 2. Tonic maintained or rhythmic grouped firings of the T-C neurones recorded as extracellular units with microelectrode in the thalamus were in the majority suppressed by high frequency RF stimulation during and often for a short time after the stimulation, and they showed later tonic discharges for many seconds or minutes. Intracellular recording from the T-C neurones revealed hyperpolarizing potential changes corresponding to the suppression on high frequency RF stimulation. Field potential analysis in the VA nucleus indicated that the hyperpolarization is ascribed at least in part to IPSPs elicited in the T-C neurones. Responses in some other types of thalamic neurones to the RF stimulation were exemplified to be compared and related with those of the T-C neurones. 3. Desynchronization of the parietal electrocorticogram coincided with the suppression of the T-C neurones and lasted for the time of the later tonic discharges, which contrasted with the rhythmic grouped discharges of the T-C neurones in association with recruiting and spindling-like responses of the cortex. Relations between the thalamo-cortical recruiting system and the ascending reticular activating system were discussed.

Adenylosuccinate synthetase (IMP: l -aspartate ligase (GDP-forming), EC 6.3.4.4) was purified about 750-fold to a homogeneous state from Yoshida sarcoma ascites tumor cells. A yield of 38% purified enzyme was achieved by a procedure including affinity chromatography on hadacidin-Sepharose 4B. Ultracentrifugal analyses showed that the molecular weight of the native enzyme was 102 000 with an s 20, w value of 4.5 and that the molecular weight in 6 M guanidine-HCl was 47 000. These values indicate that the native enzyme is composed of two subunits. The isoelectric point was determined to be 5.9 by isoelectric focusing. The optimum pH for activity was 6.8-7.0. The K m values for IMP, aspartate and GTP were calculated to be 4.1, 9.8 and 0.7 · 10 −4 M , respectively. The antibiotic, hadacidin was strongly inhibitory, causing competitive inhibition with respect to aspartate with a K 1 value of 2.5 · 10 −6 M . Nucleoside mono- and diphosphate also inhibited the enzyme activity, but their inhibitions were not apparently specific. The purified enzyme showed full activity in the presence of Mg2+, and Mg2+ could be partially replaced by Mn2+, Co2+, Ca2+ or Cu2+. Divalent metal ions, such as Cd2+, Pb2+, Zn2+, Cu2+ and Mn2+, interfered with the activity by antagonizing Mg2+, Hg2+ or PCMB inactivated the enzyme, suggesting that an SH-group may be important for activity.

Sixty-nine thalamocaudate projection neurons in ventroanterior (VA: 32 cells), centrolateral (CL: 12 cells) and centrum medianum or parafascicular (CM-Pf: 25 cells) nuclei of the cat were identified by antidromic response to stimulation of the caudate nucleus (CD). Twenty-two VA and 3 CL neurons in this sample were proved to have a branching axon projecting on both CD and the cerebral motor cortex (Mcx). Most of the branching VA neurons showed repetitive discharges synchronous with the cortical recruiting response elicited by repetitive stimulation (6-10/sec) of the pallidum. Such activities of the VA neuron which would induce the motor cortical recruiting response, were proved to be conveyed to CD.

1. Responses evoked in the cerebellar cortex by stimulation of the parietal association cortex (rostral portions of the middle suprasylvian gyrus) were recorded and analysed in cats, and were compared with those by stimulation of the motor cortex (anterior sigmoid gyrus). 2. The parietal stimulation elicited early mossy fibre and late climbing fibre responses in the cerebellar cortex. The mossy fibre responses appeared at a latency of 2.0--2.5 msec and predominantly in the lateral (hemispherical) part of the contralateral cerebellum (mainly crus I, crus II and paramedian lobules). Cutting of the inferior cerebellar peduncle produced little or no influence upon the mossy fibre responses, which suggests that the mossy fibre responses are mediated chiefly by the pontine nuclei. 3. The climbing fibre responses were recorded at a latency of 17--19 msec and markedly in the contralateral intermediate and medial parts of IV--VI lobules. The responses were easily sppressed by anaesthesia and depended on the conditions of experimental animals. The unstable appearance of the responses and their longer latencies than those of the climbing fibre responses due to stimulation of the motor cortex imply indirect pathways from the parietal association cortex to the inferior olive. 4. The predominant projection of the parietal-induced mossy fibre responses to the lateral part of the cerebellum was compared with the mossy fibre projection from the motor cortex and was discussed as an important component in the cerebrocerebellar loops.

myo-Inositol-1-phosphatase [EC 3.1.3.25] was purified from a cytosolic fraction of rat brain. The purified enzyme appeared homogeneous on SDS-polyacrylamide gel electrophoresis and its molecular weight was estimated to be 29,000. The molecular weight of the native enzyme was 55,000 as determined by molecular sieve chromatography. These values indicated that the native enzyme was composed of two identical subunits. The isoelectric point of the enzyme was 4.6. The enzyme hydrolyzed inositol-1-phosphate, 2'-AMP, 2'-GMP, beta-glycerophosphate, and alpha-glycerophosphate; the ratio of the reaction rates was 100 : 84 : 73 : 64 : 32. The Km values for inositol-1-phosphate, 2'-AMP, and beta-glycerophosphate were 1.2 X 10(-4) M, 1.9 X 10(-4) M, and 7.7 X 10(-4) M, respectively. Mn2+ and Ca2+ were strong competitive inhibitors against Mg2+, with Ki values of 3 microM and 20 microM, respectively. This result suggests that myo-inositol-1-phosphatase might be regulated by intracellular Ca2+ and/or Mn2+. Li+, which is known to show a therapeutic effect on manic-depressive disease and also to prolong the intrinsic periods of circadian rhythms in various organisms, was a potent uncompetitive inhibitor and inhibited 50% of the activity at 1 mM. The possibility that myo-inositol-1-phosphatase and inositol phospholipid metabolism are involved in circadian rhythm oscillation is discussed in terms of Li actions.

Glucose transport systems in cultured neuronal cells and astrocytes of rats were characterized by measuring the uptake of 2-deoxy-d-[3H]glucose ([3H]2-DG) into the cells. Various sugars inhibited 2-DG uptake by neuronal cells and astrocytes similarly, a finding indicating that the substrate specificities of the transporters in the two types of cells were almost the same. However, the Kmvalues for 2-DG of neuronal cells and astrocytes were 1.7 and 0.36 mM, respectively. The uptake of 2-DG was strongly inhibited by cytochalasin B. Nucleosides, such as adenosine, inosine, and uridine, inhibited 2-DG uptake competitively in both neuronal cells and astrocytes. The uptakes by both types of cells were also inhibited by forskolin, but not by cyclic AMP, an observation suggesting that forskolin bound directly to the transporters to cause inhibition. Its inhibition was competitive in astrocytes and noncompetitive in neuronal cells. Astrocytes contained a glucose transporter with a subunit molecular weight of 45K, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after photoamnity labeling using [3H]cytochalasin B as a probe.

Two types of nucleoside diphosphatase were found in rat brain. One (Type L) had similar properties to those of the liver microsomal enzyme with respect to its isoelectric point, substrate specificity, Km values, optimum pH, activation by ATP and molecular weight. The other (Type B), which separated into multiple forms on isoelectric focusing, had lower Km values and a smaller molecular weight than the Type L enzyme, and was inhibited by ATP. The Type B enzyme catalyzed the hydrolysis of thiamine pyrophosphate as well as those of various nucleoside diphosphates at physiological pH, while Type L showed only nucleoside diphosphatase activity at neutral pH. These findings suggest that the two enzymes play different physiological roles in the brain.

In view of the discrepancies in reports about the cerebral responses induced by stimulation of the cerebellar fastigial nucleus in the cat, attempts were made to re-evaluate the effects of stimulation of the fastigial nucleus in the cerebral cortex and thalamus of cats anesthetized with pentobarbital. Stimulation of the fastigial nucleus elicited responses of low amplitude bilaterally in the medial portion of the precruciate cortex in 7 out of 25 animals studied. The responses were mainly composed of a positive wave which reversed its polarity at a depth between 250 and 500 microns from the cortical surface. Presumable relay cells for the responses were detected in the ventromedial nucleus and the medial area of the ventrolateral nucleus of the thalamus. Thalamic neurones showed a tendency to repetitive spike generation with variable latencies after fastigial stimulation, while conditioning stimuli applied to the midbrain reticular formation apparently counteracted it, enhancing the probability of generation of a single spike at a shorter latency. The effect of pentobarbital anesthesia on the fastigio-thalamic transmission is discussed in relation to the inconstant appearance of cortical responses after fastigial stimulation.

The response to ramp current stimulation was studied in the pars compacta neurons in guinea pig substantia nigra slices. Although accommodation was not seen with current duration up to 1000 ms, a threshold peak emerged on the threshold-latency curve at 30-400 ms when the cell was hyperpolarized. The appearance of the peak was closely correlated with an inflection in the potential trajectory before the spike. A voltage-dependent, fast inactivating outward current may underlie these responses. They persisted in Ca2+-free solution, but disappeared when Cd2+ (0.4 mM) or Co2+ (5 mM) ions were applied extracellularly.

In guinea pig hippocampal slices, 4-aminopyridine (4-AP) in concentrations of 100-500 microM reduced the adaptation of CA3 pyramidal neurons to depolarizing stimuli, resulting in a prolongation of repetitive firing during injection of long-lasting depolarizing currents. Concurrently, there was a decrease in the 'sag' of potential after spike bursts. Furthermore, 4-AP decreased or abolished the hyperpolarizing potential (the afterhyperpolarization) which normally followed repetitive firing of the neurons. The findings suggest that 4-AP could interfere with the Ca2+-activated K+ current in hippocampal CA3 pyramidal neurons.

The role of the hypothalamus in the eating act and the regulation of food intake has recently been established in experimental animals by stimulation and destruction of the structure. The hyperphagia with obesity and the aphagia produced by the hypothalamic lesions indicates the localization of two regulatory centers, mutually antagonistic in function, i.e. the satiety center and the feeding center. The satiety center is presumedly involved in regulation of food intake responding to the changes of visceral sensations or blood concentration of metabolic products. The destruction of the ventromedial hypothalamic region has been shown to produce hyperphagia and obesity in a variety of animals. Apart from the study on the regulation of food intake, attempts have been made to elucidate other aspects of the eating behavior, that is, the motivation mechanism by observing the hunger-motivated behaviors or the conditioned responses. In hypothalamically hyperphagic rats, Miller et al. (1) have shown that their hunger-motivated behaviors are more easily depressed than in normal ones. In the experiments to present the possible involvement of the satiety center in the anorexigenic effect of amphetamine Epstein (2) and Reynolds (3) have found that the reduction of food intake induced by the drug is more marked in hypothalamically hyperphagic rats than in intact ones. From the observation that hypothalamically hyperphagic rats overate the dextrose-added diet, but refused to eat it when cellulose or quinine was added to the food which was still acceptable to normal rats, Teitelbaum (4) regarded them as finicky eaters. Epstein (2) suggested that this notion of finickiness might be extended to all feeding situations in the hypothalamus-lesioned hyperphagic rats. Some pharmacological agents have been known to reduce or enchance the appetite. One of them is amphetamine, and, with other sympathomimetic drugs, it has been often used clinically in obesity control. Schmidt and Van Meter (5) observed a depressing effect of chlorpromazine on food intake in rats, and chlordiazepoxide was reported to augment the food intake and to accelerate the increase of body weight in rats and dogs (6). The clinical observations with reserpine also suggest some effects on the appetite. In the present experiment, effects of some centrally acting drugs on the hypothalamic regulatory mechanisms of feeding have been examined by observing the eating behaviors in intact and hypothalamus-lesioned rats.

1) Augmenting and recruiting responses in the sensory cortices were examined by means of laminar field potential analysis in the cortices. These responses were characterized and interpreted as follows: Augmenting responses are a deep thalamocortical (T-C) response followed by a superficial T-C response and recruiting responses are a pure form of superficial T-C response, deep and superficial T-C responses being two elementary components constituting various cortical responses induced by thalamic stimulation (see SASAKI et al., 1970).2) Long-latency surface-negative potentials elicited in the somatosensory cortex (posterior sigmoid gyrus) by repetitive stimulation of the intralaminar thalamic nuclei were not due to recruiting responses actually generated in this area but attributable to the responses evoked in the underlying hidden cortex. Similar situations to those in the somatosensory cortex hold for “recruiting responses” recorded on the surface of the visual and auditory areas, i. e., the responses in the lateral and the ectosylvian gyri were assignable to activities generated in the underlying or neighboring hidden cortex.3) Repetitive stimulation of the thalamic sensory relay nuclei given at a low frequency failed to evoke the augmenting response in the respective cortical sensory areas. It induced in some cases incremental responses in the sensory areas of the cortex; the depth profiles in the cortex were not in accord with the characteristic feature of the augmenting response in the anterior sigmoid gyrus.4) The absence of superficial T-C responses in the form of recruiting responses as well as a component of augmenting responses in the sensory cortices suggests that there is little or no thalamocortical projection system for the superficial T-C response ending in these cortices.