FUNCTIONAL SIGNIFICANCE OF DRUG-INDUCED CHANGES IN BRAIN MONOAMINE LEVELS

The mechanism of monoaminergic i.e. adrenergic, noradrenergic, dopaminergic, and serotonergic transmission in general is discussed on the basis of observations on the effects of various agents chiefly precursors and precursor analogs, inhibitors of enzymes responsible for synthesis and degradation of monoamines, and drugs interfering with storage and release. the storage granules or vesicles of the monoaminergic nerve terminals, in which the transmitter can be visualized under the fluorescence microscope by means of a new histochemical technique, appear to have a dual function, i.e. a to serve as a store of transmitter, and b to make newly synthesized transmitter available for release by membrane depolarization. The former function does not seem to be essential, since the store can be depleted without any disturbance of transmission. The latter function seems to be essential block of the uptake mechanism of the granules by reserpine results in block of transmission.