Cholinergic but not GABAergic neuronal markers are decreased in primary neuronal cultures treated with choline mustard

Nitrogen mustard analogues of choline are potent irreversible inhibitors of high-affinity choline transport at the cholonergic presynapric nerve terminal in vitro. Ethycholine mustard aziridinium ion, and to a lesser extent choline mustard aziridinium ion, have been used as tools to chemically lesion cholinergic neurons in the central nervous system. The selectivity of these compounds as neurotoxins for cholinergic neurons in vivo has been questioned and the mechanism by which they mediate neuronal death has not been elucidated. The objective of the present study was to investigate the selectivity of choline mustard aziridinium ion on embryonic rat brain neurons maintained in primary culture. The effect of choline mustard aziridinium ion on levels of cholinergic neuronal markers was compared with markets for GABAergic neurons as a measure of neuronal specificity. Choline mustard aziridinium ion at 10 and 30 μM irreversibly inhibited hemicholinium-sensitive, high-affinity choline transport into the cultured neurons without altering sodium-dependent, high-affinity GABA transport. Similarly, incubation of the neurons for 30 min in the presence of 10 μM choline mustard aziridinium ion led to a decrease in choline acetyltransferase activity of the cultures which was maintained for 72 h; glutamic acid decar☐ylase activity was not altered under the same experimental conditions. Protein and DNA content and DNA-to-protein ratios of the choline mustard aziridinium ion-treated cultures were monitored as indicators of generalized cellular damage. Neither protein nor DNA content of the neuronal cultures were changed up to 72 h after a 30 min incubation in the presence of 10 μM choline mustard aziridinium ion indicating that cell numbers and the extent of neuronal processes were not altered. In summary, it appears that low concentrations of choline mustard aziridinium ion mediated selectivity of action for cholinergic neurons relative to GABAergic neurons maintained in vitro.