Effects of differential modulation of mu-, delta- and kappa-opioid systems on bicuculline-induced convulsions in the mouse.
The present study investigated the effects of micro-, delta- and kappa-opioid receptor agonists on seizures produced by blockade of gamma-aminobutyric acid (GABA)-mediated synaptic transmission in the mouse. The selective GABA(A) receptor antagonist bicuculline (1.25-3 mg/kg) given subcutaneously caused dose-dependent clonic-tonic convulsions. These convulsions were potentiated by the prototypic mu-opioid receptor agonist morphine given subcutaneously 20 min prior to a subconvulsive dose of bicuculline. The potentiation by morphine was completely reversed by pretreatment intraventricularly with the selective mu-opioid receptor antagonist beta-funaltrexamine (0.5 microgram/mouse). Pretreatment intraventricularly with the selective delta-opioid receptor agonists 2-methyl-4aalpha-(3-hydroxyphenyl)-1,2,3,4,4a,5,12, 12abeta-octahydro-quinolino[2,3,3-g]isoquinoline ((-)TAN-67) or [D-Pen(2,5)]-enkephalin (DPDPE) showed a dose-dependent increase in the incidence of convulsions. Pretreatment with naltrindole (2 mg/kg, s.c.), a selective delta-opioid receptor antagonist, abolished the enhancement of the bicuculline-induced convulsions by DPDPE. In contrast, pretreatment with the selective kappa-opioid receptor agonist U-50,488H (0.6-80 mg/kg, subcutaneously or 25-100 microgram/mouse, intraventricularly) produced a dose-dependent suppression of the bicuculline-induced convulsions. The inhibitory effect of U-50,488H was completely blocked by pretreatment subcutaneously with nor-binaltorphimine (5 mg/kg), a selective kappa-opioid receptor antagonist. This study demonstrates that activation of both mu- and delta-opioid receptors increases the incidence of convulsions produced by blockade of GABA-mediated synaptic transmission, while stimulation of kappa-opioid receptors has an anticonvulsive effect.
Yajima
Y
Y
Department of Toxicology, School of Pharmacy, Hoshi University, Tokyo, Japan.
Narita
M
M
Takahashi-Nakano
Y
Y
Misawa
M
M
Nagase
H
H
Mizoguchi
H
H
Tseng
L F
LF
Suzuki
T
T
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology; D000700:Analgesics / Q000494:pharmacology; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D001640:Bicuculline; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology; D003292:Convulsants; D020881:Enkephalin, D-Penicillamine (2,5)- / Q000494:pharmacology; D004830:Epilepsy, Tonic-Clonic / Q000139:chemically induced* / Q000503:physiopathology*; D007276:Injections, Intraventricular; D007279:Injections, Subcutaneous; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000502:physiology; D011957:Receptors, Opioid / Q000502:physiology*; D017465:Receptors, Opioid, delta / Q000502:physiology; D017473:Receptors, Opioid, kappa / Q000502:physiology; D017450:Receptors, Opioid, mu / Q000502:physiology; D012640:Seizures / Q000139:chemically induced / Q000503:physiopathology; D009435:Synaptic Transmission / Q000187:drug effects
D000700:Analgesics; D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D003292:Convulsants; D009292:Narcotic Antagonists; D011804:Quinolines; D011963:Receptors, GABA-A; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; C094142:TAN 67; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; C024524:beta-funaltrexamine; D009020:Morphine; D020881:Enkephalin, D-Penicillamine (2,5)-; D001640:Bicuculline