Effects of chronic morphine pretreatment on amygdaloid kindling development, postictal seizure and suppression and benzodiazepine receptor binding in rats

Abstract 

Effects of chronic morphine pretreatment on the development of amygdaloid kindling, seizure suppression and benzodiazepine (BDZ) receptor binding in rats were evaluated. The morphine-pretreated animals showed faster acquisition of seizure activity. Further evaluation of the postictal seizure suppression immediately after a fully kindled seizure demonstrated that morphine-pretreated rats had a decreased sensitivity to subsequent kindling stimulations. Twenty-four hours after the last electrical stimulation, saline-pretreated fully kindled rats showed enhanced BDZ receptor binding in dentate gyrus, and decreased binding in cingulate cortex ipsilateral to the stimulation site, compared to saline controls. Morphine-pretreated amygdala-kindled rats had significantly higher BDZ binding in piriform, entorhinal and sensorimotor cortices, basolateral and cortical amygdaloid nuclei, dentate gyrus, CA1-3 areas, substantia nigra pars reticulata and periaqueductal gray. The present study indicates that the previous experience with chronic morphine modifies the kindling process and that the enhanced BDZ receptor binding detected in our experiments may be involved in the enhanced postictal seizure suppression observed in these animals.

Keywords:  Kindling, Morphine, Seizure suppression, Benzodiazepine, GABA

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