Stimulation of synaptosomal dopamine synthesis by veratridine

Abstract

ISOLATED synaptosomal preparations maintain many of the functional properties of intact neurones¹ and the uptake of putativebiogenicamine neurotransmitters such as noradrenaline, dopamine and serotonin, is well documented^2–5. In addition, stimulation of synaptosomal catecholamine release has been demonstrated in response to deplolarising concentrations of potassium^4,6 or veratridine⁶, an alkaloid able to produce depolarisation in intact neurones by increasing sodium permeability^7,8. In intact adrenergic neurones stimulation of transmitter release is often accompanied by a concurrent increase in the rate of transmitter synthesis, possibly through a reduction in feedback inhibition of tyrosine hydroxylase^9–13. The demonstration of a link between stimulated neurotransmitter release and stimulated synthesis in synaptosomes would be an important indication of the validity of studies of synaptosomal processes in order to gain insight into the functioning of intact neurones. We report here that striatal synaptosomes maintain the ability to respond to depolarising concentrations of veratridine with a calcium-dependent tetrodotoxin-sensitive increase in dopamine synthesis.