Abstract
The vasoactive intestinal polypeptide was present in synaptosomal (nerve ending) preparations from cerebral cortex, hypothalamus, and striatum of rat brain in higher concentrations than in these tissues as a whole. The total content and relative specific activity of the peptide increased with progressive purification of the synaptosomal fractions and generally followed the distribution of known synaptosomal constituents--dopamine, norepinephrine, and lactate dehydrogenase (L-lactate:NAD+ oxidoreductase, EC 1.1.1.27). The peptide was also released from synaptosomal pellets with increased K+ concentration, and this release was Ca2+-dependent. The findings suggest a role for vasoactive intestinal polypeptide as a transmitter or modulator of synaptic function.