Abstract
The antihistamines and related drugs have been shown to have a variety of effects upon living systems, including growth inhibition of micro-organisms(1-5), inhibition of glutamate oxidation by rat brain tissue(6), and production of conduction block and depolarization of frog nerve(7). Of these effects, only one case of bacteriostatic activity(4) and one case of fungistatic activity(3) were reversible by histamine. Experiments in this laboratory have shown β-dimethylaminoethyl benzhydryl ether (Benadryl hydrochloride, Parke, Davis Company) is a potent inhibitor of the growth of the green flagellate, Chlorogonium tetragamum.
Experiments were carried out a modification of the medium of Hunter et al.(8) for fresh-watet chlamydomonads, produced by reducing the concentrations of trace metals and chelating agent to one-fifth those described for the original medium. Dilution of this medium by one-sixth its volume, changes in initial pH from 5.5 to 8.0, and the addition of the metabolites and biological materials mentioned below had no appreciable effect on the growth of Chlorogonium in this medium. The organisms were grown in 14 × 125 mm cotton-stopperedc test tubes, and incubated at 25°C with constant flourescent illumination. Populations were estimated by Tyndall-beam nephelometry† at approximately 3-hour intervals during the logarithimic growth period (about 12 hours) and at later timew when necessary. Cultures were routinely plated on bacteriological media at the end of each experiment, and data from contaminated tubes were discarded
Results. Benadryl‡ in concentrations of 1.7 × 10-5 M to 8.6 × 10-4 M causes a graded inhibition of the growth rate Chlorogonium from almost complete inhibiton at the higher. Concentrattions in this range are not lethal, since subcultues into Benadryl-free medium after 24 hours to Benadryl regularly showed normal growth.
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