The Effects of Naloxone and Interstimulation Interval on Post-Ictal Depression in Kindled Seizures

Three experiments were conducted to investigate the effects of naloxone hydrochloride on the seizure parameters (after discharge and motor seizure thresholds and durations) and post-ictal depression in kindled seizures. In Experiment 1, eight male hooded rats were exposed to four naloxone doses {2, 5, 10 mg/kg and a saline control) during a threshold testing procedure. In this factorial design, naloxone was found to have no effect on either the basic seizure parameters or post-ictal depression. Experiment 2 examined the effects of both naloxone dosage and inter­ stimulation interval (ISI) on kindled seizures. Eight male hooded rats were exposed to factorial combination of two ISIs (30 and 60 sec) and three naloxone doses (2, 10 mg/kg and a saline control) during a threshold testing procedure. Naloxone was found to significantly shorten motor seizure duration and postictal depression. Experiment 3 examined the effects of naloxone on a subsequent suprathreshold stimulation induced seizure following an initial suprathreshold stimulation. A factorial combination of four naloxone doses (2, 5, 10 mg/kg and a saline control) and two ISIs (2 and 6 min) separating the two stimulations was employed, While no main effects for either naloxone or ISI were found in the subsequent seizure activity, there was a significant interaction between naloxone and ISI for the subsequent motor seizure duration. It can be concluded from the results of the present experiments that the direction and consistency of naloxone's effects on kindled seizures remain unclear. However, the effects of ISI on seizure activity were found to be consistent with the previous literature, The role of endorphin as a possible mediator of post-ictal depression in kindled seizures does not appear primary, Differences in seizure severity between the kindling model and other drug models were discussed.