Mouse neuroblastoma clone N1E-115: a suitable model for studying the action of dopamine agonists of tyrosine hydroxylase activity.

The DOPA-content in neuroblastoma clone N1E-115 is higher than the dopamine or noradrenaline content. Blockade of tyrosine hydroxylase by alpha-methyl-p-tyrosine (1 X 10(-3) M) resulted in a decrease of cellular DOPA-content to 24.9% after 4 hr. The accumulation of DOPA in these cells which is probably due to limited activity of l-aromatic amino acid decarboxylase led us to use DOPA-content as a measure of tyrosine hydroxylase (TH) activity. Dopamine and especially apomorphine were effective at low concentrations (dopamine IC50 1 X 10(-5) M, apomorphine 2 X 10(-7) M); lisuride had no effect on TH-activity. The low effective dose of apomorphine and the failure of lisuride to influence TH-activity are comparable to the observations in striatal synaptosomal preparations and make the N1E-115 clone a suitable model for studying the mechanism of TH-regulation. However, since haloperidol (1 X 10(-5) M) did not reverse the apomorphine-induced blockade of TH, a receptor-mediated blockade of TH seems to be improbable.