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Background&Objective: Ascorbic acid, an antioxidant vitamin, is found throughout the mammalian central nervous system. Although, the centeral role of ascorbic acid is unclear, but there is good evidence that ascorbic acid modulates opiate withdrawal syndrome. This study was done to determine the effect of ascorbic acid (A.A.) on naloxone-induced withdrawal signs in morphine-dependent guinea-pigs. Materials&Methods: In this experimental study, male guinea-pigs (300-400 g 8-10 animals/group) were rendered dependent on morphine by subcutaneous (s.c.) injections of morphine sulfate 3 times a day for 3 days, and withdrawal signs were induced by intraperitoneal (i.p.) administration of naloxone (15 mg/kg) 2 h after the tenth injection of morphine sulfate on day 4 then animals were placed individually into a cylindrical glass (25 cm in diameter, 180 cm height) and the withdrawal signs were recorded over a 60-min period. Results: Chronic pretreatment of guinea-pigs with A.A., 200 mg/kg, s.c. 3 times daily for 3 days, reduced withdrawal jumping, digging, writhing, rearing, face- washing, head and body shakes, penile licking and diarrhea. The mixed dopamine D1/D2 receptor agonist apomorphine (0.5 mg/kg, s.c.) markedly antagonized the inhibitory effect of A.A. on the withdrawal signs. The effect of apomorphine was blocked by the dopamine D1 receptor antagonist SCH23390 (0.5 and 1 mg/kg, i.p.) but not by the dopamine D2 receptor antagonist sulpiride (50 mg/kg, s.c.) nor the peripheral dopamine receptor antagonist domperidone (1 mg/kg, s.c.). Conclusion: It is concluded that chronic administration of ascorbic acid inhibits opiate withdrawal, via a central dopamine D1 receptor mechanism.

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Background and Objective: Methamphetamine is a highly addictive drug associated with severe psychosocial consequences and is extensively abused. This study aimed to determine the effects of four weeks of aerobic exercise and berberine supplementation on the expression of dopamine 5 receptor and poly (adenosin diphosphat [ADP]-ribose polymerase (PARP) genes in the heart tissue of methamphetamine-exposed rats.
Methods: In this experimental study, 30 female Wistar rats were randomly allocated into five groups of six: Control, methamphetamine, methamphetamine + aerobic exercise, methamphetamine + berberine, and methamphetamine + aerobic exercise + berberine. Intraperitoneal injections of methamphetamine (10 mg/kg) and aerobic exercise and berberine consumption (100 mg/kg) were administered for 4 weeks during the withdrawal period. The expression levels of dopamine 5 receptor and PARP genes was measured using real-time polymerase chain reaction (PCR).
Results: There was no significant difference in PARP gene expression between the methamphetamine group (1.02±0.65) and the control group (1.02±0.24). Similarly, there was no significant difference in dopamine 5 receptor gene expression between the methamphetamine group (5.74±4.94) and the control group (4.76±2.63). The expression levels of PARP and dopamine 5 receptor genes following exercise (1.01±0.55 and 4.30±1.96, respectively), berberine supplementation (0.61±0.25 and 2.97±1.45, respectively), and the combined intervention (0.67±0.30 and 3.43±1.87, respectively) showed no significant differences between the groups.
Conclusion: Short-term methamphetamine induction did not induce significant changes in the expression of dopamine 5 receptor and PARP genes in the hearts of methamphetamine-exposed rats.