RESUMEN
Objective To evaluate the relationship between melatonin and development of post-herpetic neuralgia (PHN) in rats.Methods Sixty adult Wistar rats of both sexes,aged 3 months,weighing 180-230 g,were randomly divided into A-F 6 groups (n =10 each) using a random number table.Group A served as sham operation group,and inactivated herpes simplex virus type-1 (HSV-1) was inoculated.Group B served as sham operation group,and HSV-1 was inoculated.In group C,pinealectomy was performed and inactivated HSV-1 was inoculated.In group D,pinealectomy was performed,and HSV-1 was inoculated.In group E,pinealectomy was performed,inactivated HSV-1 was inoculated,and melatonin was injected intraperitoneally everyday.In group F,pinealectomy was performed,HSV-1 was inoculated,and melatonin was injected intraperitoneally everyday.HSV-1 or inactivated HSV-1 was inoculated on the left hind paw of the rats at 1 h after pinealectomy,and the dosage of melatonin was 120 mg/kg once a day.The mechanical pain response score (MPRS) was determined before inoculation and on days 1,5,10,20 and 30 post-inoculation.The development of PHN was recorded on day 30 post-inoculation.Results MPRS was significantly higher in group B than in group A,and in group D than in group B (P ＜ 0.05).MPRS was significantly lower in group F than in group D (P ＜ 0.05).PHN was not found in A,C and E groups,and the incidence of PHN was 40％,90％ and 40％,respectively.Compared with group B,the incidence of PHN was significantly increased in group D (P ＜ 0.05),and no significant change was found in group F (P ＞ 0.05).Conclusion Reduction of melatonin secretion is related to the development of PHN in rats.