Summary
Hemisection of the brains of rats was performed at a level slightly rostral to the mesencephalo-diencephalic junction. In chronic experiments (7 to 14 days after the lesion) a considerable decrease in 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels was found in the ipsilateral hemiforebrain. In acute experiments (3 to 6 h after the lesion) the effect of the lesion on synthesis and metabolism of 5-HT was investigated by estimating tryptophan, 5-hydroxytryptophan (5-HTP), 5-HT and 5-HIAA levels in different parts of the brain. In order to get an insight into the different steps in 5-HT metabolism inhibitors of enzymes or transport were used (Ro 4-4602 [N-(dl-seryl)-N1-(2,3,4-trihydroxybenzyl) hydrazine], pargyline, and probenecid). The effect of l-tryptophan loading was also investigated.
The accumulation of 5-HTP and 5-HT following inhibition of 5-HTP decarboxylase and monoamine oxidase, respectively, was not significantly influenced by the hemisection. On the other hand, the accumulation of 5-HIAA following probenecid treatment, and the disappearance of 5-HT and 5-HIAA following inhibition of 5-HTP decarboxylase and monoamine oxidase, respectively, were slightly or moderately retarded.—The tryptophan level was moderately increased on the side of the lesion.
The data indicate that a considerable synthesis and metabolism of 5-HT occurs intraneuronally even in the absence of an impulse flow. The nerve impulses induce an increased release and extraneuronal metabolism, primarily at the expense of stored 5-HT. In addition, the nerve impulses possibly cause a certain increase in 5-HT synthesis.
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Bédard, P., Carlsson, A. & Lindqvist, M. Effect of a transverse cerebral hemisection on 5-hydroxytryptamine metabolism in the rat brain. Naunyn-Schmiedeberg's Arch. Pharmacol. 272, 1–15 (1972). https://doi.org/10.1007/BF00498790
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DOI: https://doi.org/10.1007/BF00498790