Evidence for a modulatory role of catecholamines on hypothalamic somatostatin in the rat

The influence of catecholamines (CA) on hypothalamic somatostatin (HPT-SRIF) was investigated in rats by using several drugs which interfere with brain CA metabolism. Depletion of brain CA stores by alpha-methyl-rho-tyrosine (AMT) increased HPT-SRIF, while augmented brain CA levels following L-dopa administration decreased HPT-SRIF content. Blockade of dopamine beta-hydroxylase activity by disulfiram depleted brain noradrenaline (NA) and decreased HPT-SRIF. The selective increase in brain NA stores caused by threo-dihydroxyphenylserine (DOPS) also produced an increase in HPT-SRIF. Increased dopamine (DA) and decreased NA levels after disulfiram + L-dopa (1 h) treatment did not modify HPT-SRIF, whereas unaltered NA and greatly increased DA levels following disulfiram + L-dopa (2 h) treatment produced a drastic reduction of HPT-SRIF. The results suggest that DA and NA exert an influence on HPT-SRIF, supporting previous observations.