Abstract
Abstract— Crude synaptosomal (P2) preparations were obtained from the cerebella of rats in which the granule cell population had been selectively reduced by X‐irradiation treatment and from the cerebella of control animals. In the P2 fraction from control cerebella, the level of glutamate was greater than any other of the 5 amino acids measured and was 2‐fold higher than taurine, which was present at the next highest level. The content of taurine was slightly higher than that found for aspartate and was 3‐fold greater than that observed for GABA. Alanine and glycine were present in the lowest amounts. The levels of glutamate and aspartate were significantly (P < 0.05) lower by 25 and 15%, respectively, in the P2 fraction isolated from the X‐irradiated cerebella in comparison to control values. The content of taurine, GABA, glycine, and alanine were not changed by the X‐irradiation treatment. The uptake of 1.0 μm‐l‐[3H]glutamate and l‐[3H]aspartate was reduced approx 20% by X‐irradiation treatment, whereas the uptake of 1.0 μm‐[3H]GABA and [3H]taurine was unchanged. A more detailed kinetic analysis of l‐[3H]glutamate uptake revealed there was a 20% decrease in the Vmax value with X‐irradiation treatment and no change in the apparent Km value.In a second study, the uptake of l‐[3H]glutamate, l‐[3H]aspartate and [3H]GABA was measured using P2 fractions obtained from the cerebella of rats in which the population of granule, stellate and basket cells had been reduced by X‐irradiation treatment. The uptake of 1.0μm‐l‐[3H]glutamate, l‐[3H]aspartate and [3H]GABA was significantly (P < 0.05) reduced to 57, 68, and 59%, respectively, of control values. A more detailed kinetic analysis of [3H]GABA uptake revealed no significant change in the apparent Km and a 35% decrease in the Vmax value.The data are discussed in terms of glutamate being the excitatory neurotransmitter released from granule cells and GABA being the inhibitory neurotransmitter released from basket cells.
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