Abstract
We examined the effects of parathyroid hormone (PTH) applied in physiological doses on the entry of 45Ca2+, release of 3H-GABA, and also on the contents of 1,2-diacylglycerol (DAG) and cAMP in preparations of synaptosomes obtained from the brain cortex of mongrel albino rats. It was found that PTH intensified 45Ca2+ entry in the synaptosomes. Potassium depolarization of the synaptosomal membranes did not considerably influence the entry of these ions under the influence of PTH. At the same time, evoked 45Ca2+ entry was greater than the spontaneous one in control preparations. Spontaneous release of 3H-GABA increased under the influence of PTH. At the same time, there was no additional release of 3H-GABA under depolarization conditions. Applications of PTH increased the contents of cAMP and DAG in the examined nerve terminals. It is supposed that increases in the levels of the above messengers predetermine activation of the corresponding protein kinases and phosphorylation of membrane proteins. This, finally, leads to realization of the hormonal signal, namely intensified release of the neurotransmitter.
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