Stimulation of synaptosomal uptake of neurotransmitter amino acids by insulin: possible role of insulin as a neuromodulator.

Insulin stimulates in a dose-dependent manner (concentration range of 0.1 - 10 microM) the synaptosomal uptake of amino acids characterized by high-affinity, Na+-dependent, veratridine-sensitive transport systems. This stimulation is observed in synaptosomes prepared from each of several regions of the adult rat brain. Both the initial rate of amino acid uptake and the overall capacity for amino acid accumulation are increased. Since these transport systems have been associated with the neurotransmitter role of the amino acids, we postulate that insulin can modulate neurotransmission in the rat central nervous system by increasing the efficiency of neuroactive amino acid reuptake.