Catecholamine-angiotensin II receptor interaction in primary cultures of rat brain

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Abstract
Neuron-enriched primary cultures from 1-day-old rat brains have been used to study the influence of catecholamines on angiotension II receptors. Treatment of cultures with alpha-methyl-p-tyrosine caused a time- and concentration-dependent increase in the specific binding of 125I-angiotensin II and a decrease in neuronal norepinephrine and dopamine contents. A maximum increase of 75% in the binding and a decrease of 67% in catecholamine content was observed with 400 microM alpha-methyl-p-tyrosine. Removal of alpha-methyl-p-tyrosine from cultures resulted in the recovery of catecholamine levels and decrease in 125I-angiotensin II binding to control levels. In contrast, treatment of cultures with pargyline caused decreases in the binding of 125I-angiotensin II and increases in catecholamine levels in neuronal cultures. Scatchard analysis demonstrated that an increase in 125I-angiotensin II binding by alpha-methyl-p-tyrosine was due to an increase in the affinity of receptors for angiotensin II without changes in the number of angiotensin II binding sites. The results obtained here indicate that angiotensin II binding to neuron-enriched cultures is reciprocally related to the levels of neuronal catecholamines.