Positive allosteric modulator of GABAB receptor alters behavioral effects but not afterdischarge progression induced by partial hippocampal kindling.

Abstract Hippocampal seizures decreased the function of GABA B receptors, which may further increase seizure susceptibility and contribute to development of schizophrenia-like behaviors. Recent literature indicates that GABA B receptor agonist may normalize schizophrenia-like behaviors and prevent drug-induced behavioral sensitization. We hypothesized that positive modulation of GABA B receptor function during seizure induction will reduce seizure-induced schizophrenia-like behaviors. Using a partial hippocampal kindling model, afterdischarges were induced after injection of saline or dimethyl sulfoxide (vehicle-kindled rats), or a GABA B receptor positive allosteric modulator CGP7930, at 1 mg/kg i.p. (CGP1-kindled) or 5 mg/kg i.p. (CGP5-kindled). The increase in the primary afterdischarge duration during kindling was not different among the groups. However, the CGP5-kindled group showed a lower afterdischarge starting frequency as compared to vehicle-kindled or CGP1-kindled groups. Partial hippocampal kindling (21 afterdischarges) resulted in decreased prepulse inhibition and decreased gating of hippocampal auditory evoked potentials in vehicle-kindled and CGP1-kindled rats, as compared to saline-injected non-kindled rats, recorded 3–4 days after the last afterdischarge. However, CGP5-kindled rats showed normal prepulse inhibition and hippocampal auditory gating (compared to non-kindled rats), which was significantly higher than the respective measure in vehicle-kindled rats. CGP5-kindled group also showed methamphetamine–induced locomotion that was significant lower than the vehicle-kindled or CGP1-kindled group, but slightly higher than the saline-injected non-kindled rats. In conclusion, this study provides original data that a GABA B receptor positive allosteric modulator could therapeutically prevent or normalize some seizure-induced behavioral disruptions in a model of temporal lobe epilepsy.