Involvement of delta-opioid receptors in pentylenetetrazol kindling development and kindling-related processes in rats

The role of delta-opioid receptors on the development of kindling induced b y the convulsant pentylenetetrazol (37.5 mg kg(-1) i.p.) was investigated i n rats. Besides the seizure development, the kindling induced enhancement o f glutamate binding and the kindling-induced learning deficit were examined . A clear depression of kindling development by blocking of delta-opioid re ceptors by intracerebroventricular administration of naltrindole (10 nmol/5 mu l) was found. In an acute convulsion test performed 8 days after kindli ng completion, animals pretreated with naltrindole during kindling inductio n showed lower seizure stages compared to saline-pretreated kindled animals . The kindling-induced increase in hippocampal glutamate binding was comple tely prevented by naltrindole, whereas the kindling-induced learning defici t was not influenced. The learning performance of control animals pretreate d with naltrindole was very low. It was hypothesized that the various conse quences of kindling induction could be influenced separately. Summarizing the results, an involvement of the delta-opioid system in mecha nisms underlying chemical kindling was clearly demonstrated. Interactions o f endogeneous opioid systems with glutamatergic transmission were suggested .