title: Circadian-rhythm-dependent effects of L-NG-nitroarginine methyl ester (L-NAME) on morphine-induced analgesia.
abstract: Circadian changes in the interactions between L-NG-nitroarginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, and morphine-induced antinociception were investigated by the mouse hot-plate test. Both the basal pain sensitivity and morphine-induced analgesia undergo significant 24 h variations. L-NAME (40 mg/kg, i.p.) alone did not show any antinociceptive activity, but potentiated morphine-induced analgesia when combined with morphine at all injection times. In terms of percentage absolute potentiation (%AP), L-NAME dramatically augmented the analgesic effect of morphine in the late dark period at 19 hours after lights on (HALO). It is concluded that nitric oxide (NO) is involved in the modulation of the analgesic effect of morphine; thus, the L-NAME and morphine combination might be beneficial in alleviating pain.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Gazi University, Ankara, Turkey. zengil@tr-net.-net.tr
authors.forename: H Z
authors.initials: HZ
authors.lastname: Güney
authors.forename: C Z
authors.initials: CZ
authors.lastname: Görgün
authors.forename: B
authors.initials: B
authors.lastname: Tunçtan
authors.forename: O
authors.initials: O
authors.lastname: Uludağ
authors.forename: U
authors.initials: U
authors.lastname: Hodoğlugil
authors.forename: N
authors.initials: N
authors.lastname: Abacioğlu
authors.forename: H
authors.initials: H
authors.lastname: Zengil
mesh_terms: D000698:Analgesia; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D051379:Mice; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage / Q000494:pharmacology*; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000188:drug therapy; D010147:Pain Measurement
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D009020:Morphine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester