Differential regulation of neuropeptide Y and catecholamine production in superior cervical ganglion cultures

Abstract

Primary cultures of newborn rat superior cervical ganglion (SCG) neurons grown in complete serum-free medium have been used to study the regulation of catecholamine and neuropeptide Y (NPY) production. The levels of mRNA for preproNPY and for tyrosine hydroxylase were determined, and the rates of synthesis and accumulation of NPY and catecholamines were measured. Drugs which effectively blocked accumulation of newly synthesized catecholamines (tyramine, reserpine) had no effect on NPY synthesis and accumulation. The catecholamine uptake blocker desipramine and the α 2-adrenergic receptor agonist clonidine inhibited accumulation of newly synthesized catecholamines, but only after prolonged exposure to drug; NPY synthesis and accumulation were unaltered by these treatments. The α 2-adrenergic receptor antagonist yohimbine had no effect on catecholamine or NPY synthesis or accumulation, regardless of the time of treatment. The net synthesis and accumulation of catecholamines and NPY decreased in parallel in response to treatment with phorbol esters, and increased in parallel in response to treatment with glucocorticoids; there was no change in the mRNA levels for tyrosine hydroxylase or preproNPY following either treatment. The levels of tyrosine hydroxylase or preproNPY mRNA were increased following treatment with dibutyryl cyclic AMP, with no change in the net synthesis and accumulation of catecholamines or NPY. Thus, the levels of mRNA for preproNPY and tyrosine hydroxylase are not faithful indicators of the rate of catecholamine or peptide production under several treatment conditions. The complex pattern of regulation of catecholamine and NPY production in SCG neurons grown under closely controlled conditions provides an ideal system in which to examine neuronal regulation of neurotransmitter and neuromodulator production.