Rat brain cells in primary culture: visualization and measurement of catecholamines

Catecholamines have been visualized and quantified in primary cultures of whole rat brain. Twenty-one-day old cultures treated with glyoxylic acid and viewed under a fluorescence microscope revealed neurons stained specifically with blue-green catecholamine fluorescence. Brightly stained multipolar cell bodies were seen, along with stained neurites and varicosities, and there was no staining associated with the non-neuronal portion of the culture. Twenty-one-day-old non-neuron-enriched cultures contained 10-20 times less norepinephrine and dopamine than cytosine arabinoside-treated neuron-enriched cultures. The latter cultures contained 10-12 times more norepinephrine than 1-day-old rat brains, demonstrating maturation and differentiation of the cultured neurons. Norepinephrine levels of neuron-enriched cultures were, however, 3 times less than those in 21-day-old rat brains. The cultured neurons had the ability to synthesize catecholamines since levels were decreased with alpha-methyl-p-tryosine. On the other hand, the growth medium contained significant amounts of norepinephrine, but did not have the ability to synthesize catecholamines. It may be concluded that the cellular catecholamines are not derived from the medium in any great amounts. This study provides the basis of a system in which to examine catecholaminergic neurotransmission and peptide catecholamine interactions at the cellular level under semi-defined conditions.