The effect of 6-hydroxydopamine, reserpine and cold stress on the neuropeptide Y content of the rat central nervous system.

Neuropeptide Y has previously been detected in neurons throughout the rat brain and spinal cord. On histochemical grounds, the neuropeptide Y-containing cell bodies have been subdivided into two groups: those in the brain stem in which colocalization with noradrenaline and adrenaline has been demonstrated and those in other brain regions where no catecholamine coexistence is found. In this paper the regional distribution of neuropeptide Y has been investigated in the rat brain by a specific neuropeptide Y radioimmunoassay, before and after the destruction of catecholaminergic nerve terminals by the administration of intraventricular 6-hydroxydopamine. Despite massive reductions in brain catecholamines, the neuropeptide Y level was unchanged in the cerebral cortex, striatum, spinal cord and hippocampus. A minor reduction in neuropeptide Y was found in the hypothalamus. Reserpine treatment, which is known to deplete brain nerve terminal stores of catecholamines, likewise did not result in any loss of neuropeptide Y. Cold stress which increases noradrenergic turnover in the rat brain stem had no effect on neuropeptide Y levels. These results suggest that the bulk of neuropeptide Y in the rat brain and spinal cord may not be stored in catecholaminergic nerve terminals.