enkephalin-met--ala(2)- and Seizures

Microinfusion of morphine sulfate (50 nmol), [d-Ala2]-Met-enkephalin (35 nmol) or dynorphin A 1-13 (1 nmol) bilaterally into the substantia nigra significantly attenuated seizures induced by maximal electroshock in rats. This action was accompanied by stereotyped behavioral hyperactivity. These anticonvulsant and behavioral effects were antagonized by systemic naloxone administration; neither effect was observed after intranigral microinjection of dynorphin A 1-17 amide (1 nmol). These results are consistent with a mu opiate receptor-mediated inhibition of substantia nigra efferent neurons, and with the proposal that bilateral inhibition of nigral efferents attenuates seizure propagation. However, intranigral morphine failed to alter the severity of i.v. bicuculline seizures, indicating that opiate-mediated inhibition in substantia nigra is distinct from that produced by gamma-aminobutyric acid.

Topics: Animals; Bicuculline; Electroshock; Enkephalin, Methionine; Male; Morphine; Naloxone; Narcotics; Rats; Rats, Inbred Strains; Receptors, GABA-A; Receptors, Opioid; Receptors, Opioid, kappa; Seizures; Substantia Nigra

Experiments on rats with electrochemotrodes implanted in the left and right hippocamp have shown that in epileptogenic foci created by microinjections of met-enkephalin or D-ala-2-met-enkephalin into the hippocamp, acetylcholinesterase activity (AChE) was diminished. It is assumed that reduction in AChE activity is an adaptive mechanism by which the excitability of hippocampal inhibitory basket cells, which are sensitive to acetylcholine, is increased.

Topics: Acetylcholinesterase; Animals; Electroencephalography; Enkephalin, Methionine; Epilepsies, Partial; Female; Hippocampus; Male; Rats; Seizures

Topics: Animals; Anticonvulsants; beta-Endorphin; Dose-Response Relationship, Drug; Endorphins; Enkephalin, Methionine; Enkephalins; Etorphine; Flurothyl; Male; Morphinans; Naloxone; Rats; Rats, Inbred Strains; Seizures; Structure-Activity Relationship