Role of nitric oxide in the acquisition and expression of apomorphine- or morphine-induced locomotor sensitization.
In the present study, the effects of L-arginine, a nitric oxide (NO) precursor, and N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, on apomorphine- or morphine-induced locomotor sensitization in male albino mice were investigated. Our data showed that subcutaneous (s.c.) injection of apomorphine (2-10 mg/kg) or morphine sulphate (5-50 mg/kg) significantly increased locomotor behaviour in a dose-dependent manner. Intraperitoneal (i.p.) administration of L-arginine (100 mg/kg) increased locomotor activity, whereas L-NAME (20 mg/kg) decreased it. L-Arginine and L-NAME increased and decreased apomorphine- or morphine-induced locomotions, respectively. The locomotor behavioural response was enhanced in mice pretreated with apomorphine (2 mg/kg, daily x3 days) or morphine (10 mg/kg, daily x3 days) alone, indicating that sensitization had developed. Administration of L-arginine 30 min before each of three daily doses of apomorphine or morphine increased the development of sensitization, while administration of L-NAME 30 min before each of three daily doses of apomorphine or morphine decreased the acquisition of sensitization induced by apomorphine or morphine. Administration of L-arginine significantly increased and L-NAME significantly and dose-dependently decreased the expression of both apomorphine- and morphine-induced sensitization. The results indicate that NO may be involved in the acquisition and expression of apomorphine- or morphine-induced sensitization.
Zarrindast
Mohammad-Reza
MR
Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. zarinmr@ams.ac.ir
Gholami
Azam
A
Sahraei
Hedayat
H
Haeri-Rohani
Ali
A
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*
D009569:Nitric Oxide; D009020:Morphine; D001058:Apomorphine; D019331:NG-Nitroarginine Methyl Ester