The threshold for limbic seizures in rats is decreased by intranigral morphine.
Microinjection of morphine hydrochloride into the substantia nigra pars reticulata, bilaterally, converts non-convulsant dose of pilocarpine hydrochloride, 100 mg/kg, into a convulsant one. The ED50 of morphine for the generation of seizures after pilocarpine, 100 mg/kg, is 3.8 nmol (2.5-5.8). Electrographic and behavioral monitoring both show a pattern of convulsant activity similar to those produced by pilocarpine in doses exceeding 350 mg/kg. Morphological analysis of frontal forebrain sections reveals epilepsy-related damage to the hippocampus, thalamus, olfactory cortex, substantia nigra, neocortex and amygdala. The proconvulsant action of morphine in the substantia nigra is reversed by co-administration of naloxone hydrochloride. The results show that the threshold for limbic seizures may be modulated by opiates in the substantia nigra.
D000818:Animals; D003292:Convulsants; D004569:Electroencephalography; D008032:Limbic System / Q000503:physiopathology*; D008297:Male; D009020:Morphine / Q000627:therapeutic use*; D010862:Pilocarpine; D051381:Rats; D011919:Rats, Inbred Strains; D012640:Seizures / Q000188:drug therapy / Q000503:physiopathology*; D013378:Substantia Nigra / Q000187:drug effects / Q000503:physiopathology*
D003292:Convulsants; D010862:Pilocarpine; D009020:Morphine