Role of nitric oxide in the rat hippocampal CA1 in morphine antinociception.
In the present study, the effects of intra-hippocampal CA1 injections of l-arginine, a nitric oxide (NO) precursor and N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, on morphine-induced antinociception in rat formalin test were investigated. To induce inflammation pain, formalin (50 microl at 2.5%) was injected into the right hind-paw of male Wistar rats prior to testing. Morphine (3-9 mg/kg) was injected intraperitoneally (i.p.) 10 min before injection of formalin. The present study shows that administration of L-arginine (0.08, 0.15, 0.3, 1.0 and 3.0 microg/rat), but not L-NAME (0.15, 0.3 and 1.0 microg/rat), 5 min before formalin injection reversed morphine-induced antinociception at the early phase of formalin test. However, both drugs blocked morphine antinociception at the late phase of the test, but none of these drugs elicited any response by themselves at the tonic phase when injected alone. Moreover, the response to l-arginine was potentiated by L-NAME pre-treatment. It should be noted that a single injection of both L-arginine and L-NAME showed nociceptive effect at the early phase of the test. The present study reveals an expression of NADPH-diaphorase in the rat brain samples administered by L-arginine. Expression of NADPH-d is decreased in the samples which were pre-injected with L-NAME. This study suggests NO participation in the rat hippocampal CA1 area in morphine-induced antinociception.
Hashemi
Mahboobeh
M
Department of Biology, Faculty of Basic Sciences, Shahed University, Tehran, Iran.
Karami
Manizheh
M
Zarrindast
Mohammad Reza
MR
Sahebgharani
Moosa
M
D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001120:Arginine / Q000008:administration & dosage / Q000494:pharmacology; D056547:CA1 Region, Hippocampal / Q000187:drug effects* / Q000378:metabolism; D002491:Central Nervous System Agents / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005557:Formaldehyde; D007249:Inflammation / Q000139:chemically induced / Q000188:drug therapy / Q000378:metabolism; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009252:NADPH Dehydrogenase / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010146:Pain / Q000139:chemically induced / Q000188:drug therapy* / Q000378:metabolism; D010147:Pain Measurement; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D000701:Analgesics, Opioid; D002491:Central Nervous System Agents; D004791:Enzyme Inhibitors; D005557:Formaldehyde; D009569:Nitric Oxide; D009020:Morphine; D001120:Arginine; D019001:Nitric Oxide Synthase; D009252:NADPH Dehydrogenase; D019331:NG-Nitroarginine Methyl Ester