Galphimine-B modifies electrical activity of ventral tegmental area neurons in rats.

Galphimine-B (G-B) is a bioactive compound isolated from the plant Galphimia glauca Cav. (Malpighiaceae) with central nervous system depressant properties previously described. In the present study, extracellular spiking activity records in either somatosensorial cortex or ventral tegmental area (VTA) neurons, were performed in rats after i.p. or local administration of G-B. None of the cortical neurons displayed significant changes induced by any of the applied doses. In VTA cells, two patterns of electrical discharge were recorded, bursting (57%) and nonbursting (43%) types. Systemic administration of G-B induced excitatory effects in neurons with a bursting firing pattern and mixed responses on nonbursting units. When this compound was applied locally by microiontophoresis, most of the bursting and nonbursting spiking neurons showed a firing depression and only a few of the nonbursting neurons showed an increment of discharge frequency. These results are important since VTA is a major dopaminergic center responsible for the innervation of the prefrontal cortex, nucleus accumbens and entorhinal region. These areas are targets for the action of antipsychotic drugs.