Interaction of the natural anxiolytic Galphimine-B with serotonergic drugs on dorsal hippocampus in rats.
Galphimine-B (G-B) is a nor-seco triterpene with an anxiolytic-like effect obtained from the plant species Galphimia glauca Cav. By means of a double blind clinical trial, it has been demonstrated that the extract from this plant, standardized in G-B content, possesses therapeutic effectiveness in patients with generalized anxiety. The mechanism of action of this compound remains unknown to date, but it has already demonstrated a non interaction with the γ-aminobutyric acid (GABA)ergic system. For this reason, the objective of this work was to evaluate the pharmacological interaction between G-B with the 5-hydroxytryptamine 1A (5HT(1A)) and 5-hydroxytryptamine 2A (5HT(2A)) serotonergic receptors on CA1 neurons of hippocampus. Electrophysiological records were performed as the frequency of discharge of in vivo CA1 cells from dorsal hippocampus in rats. G-B was able to increase the frequency of discharge of neurons of the CA1 cells with some characteristics that support an interaction with the serotonergic system in this zone. It was demonstrated that this triterpene modulates the induced response of 5HT(1A) receptors, in an allosteric manner. This effect demonstrated an interaction between G-B and the serotonergic system in dorsal hippocampus and evidenced that the mechanism of action of this compound could involve a complex series of actions on different neurotransmitter systems related with the anxiety disorder.