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Carbenoxolone (CBX), the succinyl ester of glycyrrhetinic acid, is an inhibitor of gap junctional intercellular communication. We have tested its possible effects upon two genetic animal models of epilepsy (WAG/Rij rats and lethargic (lh/lh) mice). Systemic administration of CBX was unable to significantly affect the occurrence of absence seizures in WAG/Rij rats. In particular, intravenous (5-40 mg/kg) or intraperitoneal (i.p.; 10-80 mg/kg) administration of CBX was unable to significantly modify the number and duration of spike-wave discharges (SWDs) in WAG/Rij rats, whereas the bilateral microinjection (0.05, 0.1, 0.5 and 1 microg/0.5 microl) of CBX into nucleus reticularis thalami (NRT) and nucleus ventralis posterolateralis (VPL) thalami produced a decrease in the duration and the number of SWDs. Bilateral microinjection of CBX into nucleus ventroposteromedial (VPM) thalami did not produce any significant decrease in the number and duration of SWDs. On the contrary, i.p. (5-40 mg/kg) or intracerebroventricular (0.5, 1, 2 and 4 microg/2 microl) administration of CBX in lh/lh mice induced a marked decrease in the number and duration of SWDs in a dose-dependent manner. At the doses used no movement disorders, or other behavioural changes, were recorded in both WAG/Rij rats and lh/lh mice. No effects were observed in both animal models following systemic or focal administration of glycyrrhizin into the same brain areas where CBX was shown to be effective.

Carbenoxolone (CBX), the succinyl ester of glycyrrhetinic acid, is an inhibitor of gap junctional intercellular communication. Systemic administration of CBX was able to decrease the seizure severity score and to increase the latency time of seizure onset in genetically epilepsy prone rats (GEPRs). In particular, intravenous or intraperitoneal administration of carbenoxolone (5-30 mg/kg) produced a dose-dependent and significant reduction in the clonic and tonic phases of the audiogenic seizures in GEPRs. The anticonvulsant doses were not associated with an impairment of motor coordination. The bilateral microinjection of CBX (0.001-0.50 microg/0.5 microl) into the inferior colliculi, the substantia nigra (pars reticulata or compacta) and the inferior olivary complex was able to reduce the seizure severity score in a dose-dependent manner. The anticonvulsant effects were longer lasting after focal microinjection than after systemic administration. No anticonvulsant effects were observed following focal bilateral microinjections of glycyrrhizin into the same brain areas where CBX was shown to be effective.