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The contents of phosphoinositides, ATP, glucose and lactate in leg and claw nerves of the lobster were determined. Nerves were also analysed after cyanide poisoning, after electrical stimulation, and 1 h after removing the leg from the lobster. Cyanide poisoning decreased the levels of ATP and glucose and increased the content of lactate but did not alter the levels of phosphoinositides. Nerves left in situ for 1 h after disconnection from the central nervous system exhibited a decrease in the content of tri-phosphoinositides (TPI) of 50 per cent, without changes in ATP, glucose or lactate. The TPI change was reversed after incubation for 1 h in oxygenated seawater. Nerves labelled in vivo with 32P were removed and stimulated at 50 Hz for 5 min. The turnover of TPI phosphorus increased on stimulation in both normal and cyanide-poisoned nerves. In contrast, turnover of ATP increased after stimulation in normal nerves but not in cyanide-treated nerves. We sought to determine whether polyphosphoinositides play a greater role in resting metabolism of the nerve or in the conducting mechanisms. Our results make more likely the involvement of TPI in permeability changes of neural membranes during excitation.

— Further investigations have been made into ergothioneine in the brains of several mammalian species, and the distribution of ergothioneine in the brain of the ox is described. It has not been possible to confirm many of the findings of earlier workers and the results do not appear to support their conclusion that ergothioneine is identical with the cerebellar factor.

— Some metabolic and biochemical effects of fluorocitrate were studied in vivo in rat brain and cat spinal cord. During the preconvulsant and convulsant phases of fluorocitrate poisoning the contents of free glutamate, glutamine and aspartate declined progressively, while that of alanine increased. Incorporation of 14C from [U-14C]glucose into these amino acids also decreased, although somewhat more gradually. GABA exhibited a biphasic change, its content rising after an initial decrease while its relative specific activity rose initially and subsequently diminished. Incorporation of 14C from [U-14C]glucose and [U-14C]lysine into neural protein declined sharply. The citric acid content rose markedly in rat brain and cat spinal cord. In rat brain the glycogen content declined but ATP and ammonia contents were unchanged. The significance of these results with respect to energy metabolism and the possible mechanism of the convulsions during fluorocitrate poisoning is discussed.

— The glutamic acid decarboxylase has been purified from the lobster central nervous system. Potassium ion (0-075 m) and β-mercaptoethanol (0-025 m) were essential for enzyme activity. Enzyme had about 60 per cent of its optimal activity in the absence of added pyridoxal phosphate. Carbonyl reagents (10−4m-hydroxylamine or amino oxyacetic acid) would abolish this residual activity. The pH optimum of the enzyme was about 8-0. Standard Michaelis-Menten kinetics were applied to the decarboxylation of glutamate and a Km of 0.02 m was calculated. GABA inhibited the reaction (Ki= 1.25 × 10−3m), but the inhibition showed anomalous behaviour when graphed by the method of Lineweaver and Burk (1934). The GABA inhibition resembled competitive inhibition, but curves rather than straight lines intersecting at a common point on the velocity axis were obtained. This effect remains unexplained. Preliminary studies failed to reveal any subunit structure of the enzyme. The sedimentation coefficient (.S20.w) was 6-55 in a sucrose density gradient in an ultracentrifuge. This was unchanged by the addition of any of the agents that influence enzyme activity. The subcellular localization of the decarboxylase was explored in crude homogenates of lobster central nervous system prepared in various ways. The major proportion (about 90 per cent) of the enzyme activity was in the soluble fraction.‘Particulate’enzyme could be prepared, but gentle suspension of this material in buffer liberated most of the activity. A contaminant in the radioactive substrates led to the production of radioactive GABA without the simultaneous evolution of CO2. In this case, GABA production required active enzyme but was not an exclusive property of the glutamic decarboxylase activity.

— Evidence is presented that glycine is taken up by two different transport systems in rat CNS tissue slices; one system has relatively low affinity for glycine (Km= 300 μm) and predominates in cerebral cortex, cerebellum and mid-brain, the other has a higher affinity for glycine (Km= 40 μm) and is detectable only in spinal cord, medulla and pons. The low affinity transport system appears to be shared by other small neutral amino acids, whereas the high affinity system is very specific for glycine. Both transport systems were shown to be present in particles in homogenates of CNS tissue by incubation with glycine in vitro, and subcellular fractionation studies suggested that synaptosomes were partly responsible for such uptake. Various substances were tested as inhibitors of the high affinity uptake system for glycine in spinal cord slices; the most potent inhibitors were p-chloro-mercuriphenylsulphonate, N-ethylmaleimide, chlorpromazine, imipramine, desipramine, hydrazinoacetic acid and haloperidol. No competitive inhibitors of the high affinity glycine uptake were found. It is suggested that the high affinity transport system is associated with inhibitory synapses where glycine is a transmitter.