Effects of naloxone on hippocampal seizure activity

Although the presence of several types of opiate receptors and ligands has been demonstrated within the hippocampus, little is known about the circumstances in which endogenous opiates may be released. Previous studies have suggested that opiates may be involved in producing seizure activity within the hippocampus, or alternatively, that they may be released by seizure activity within the limbic system to prolong the period of postictal depression and thereby prevent the recurrence of seizures during this period. In this experiment we examined the effect of opiate receptor blockade produced by 20 mg/kg ip naloxone on the duration of afterdischarge produced by high-frequency hippocampal stimulation and on inhibition of subsequent seizure activity in male Sprague-Dawley rats. Contrary to the stated hypotheses, naloxone had no effect on either measure.