Changes in the amount and distribution of neuronal alkaline and acid phosphatase after chronic exposure of cultures of cingulate cortex to antidepressant drugs.

Enzyme histochemistry was used to examine alkaline and acid phosphatases in cultures of embryonic rat cingulate cortex after 14 days exposure in vitro to two tricyclic antidepressants (amitriptyline and desipramine) and two non-tricyclic antidepressants (mianserin and citalopram). An increased amount of acid phosphatase reaction product was observed in lysosomes of neurons in cultures treated chronically with the non-tricyclic antidepressants, mianserin or citalopram. More strikingly, reaction product was also present in the inner lamellae of the Golgi apparatus after this treatment, but never in controls. These observations suggest that non-tricyclic antidepressants significantly increase the rate of degradative processes in cingulate neurons. In cultures, treated chronically with desipramine or amitriptyline, pre- and postsynaptic membranes contained heavy deposits of alkaline phosphatase reaction product, whereas in control cultures not exposed to these drugs the corresponding membranes were entirely devoid of reaction product. An increase in the amount of alkaline phosphatase reaction product was also observed on the plasma membranes of neuronal cell bodies. These observations suggest that chronic exposure to antidepressants may influence transmembrane transport in cingulate neurons.