Kava pyrones exert effects on neuronal transmission and transmembraneous cation currents similar to established mood...

1. Antiepileptic drugs that are successful as mood stabilizers, e.g. carbamazepine, valproate and lamotrigine, exhibit a characteristic pattern of action on ion fluxes. As a common target, they all affect Na+- and Ca2+ inward and K+ outward currents. 2. Furthermore, they have a variety of interactions with the metabolism and receptor occupation of biogenic amines and excitatory and inhibitory amino acids, and, by this, also influence long- term potentiation (LTP) to different degrees. 3. The kava pyrones (+/-)-kavain and dihydromethysticin are constituents of Piper methysticum. Anticonvulsant, analgesic and anxiolytic properties have been described in small open trials. 4. In the studies summarized in this article the effects mainly of (+/-)-kavain were tested on neurotransmission and especially on voltage gated ion channels. It is assumed that effects on ion channels may significantly contribute to clinical efficacy. 5. Experimental paradigms included current and voltage clamp recordings from rat hippocampal CA 1 pyramidal cells and dorsal root ganglia as well as field potential recordings in guinea pig hippocampal slices. 6. The findings suggest that (i) kava pyrones have a weak Na+ antagonistic effect that may contribute to their antiepileptic properties (ii) that they have pronounced L- type Ca2+ channel antagonistic properties and act as an positive modulator of the early K+ outward current. These two actions may be of importance for mood stabilization. (iii) Furthermore, kava pyrones have additive effects with the serotonin-1A agonist ipsapirone probably contributing to their anxiolytic and sleep- inducing effects. (iv) Finally, they show a distinct pattern of action on glutamatergic and GABAergic transmission without affecting LTP. The latter, however, seems not to be true for the spissum extract of Kava where suppression of LTP was observed. 7. In summary, kava pyrones exhibit a profile of cellular actions that shows a large overlap with several mood stabilizers, especially lamotrigine.