ABSTRACT
Objective To evaluate the effect of dezocine on the c-fos expression in neurons in the midbrain periaqueductal gray in a rat model of incisional pain.Methods Thirty-six pathogen-free healthy adult male Wistar rats,weighing 250-300 g,were divided into 3 groups (n =12 each) using a random number table:control group (group C),incisional pain group (group I) and dezocine group (group D).A 1 cm longitudinal incision was made through skin,fascia and muscle of the plantar aspect of the right hind paw in sevoflurane-anesthetized rats.In group C,the rats were only anesthetized and underwent no operation.In group I,0.9％ sodium chloride solution 2 ml was injected via the caudal vein at 15 min before the model was established.In group D,dezocine 1 mg/kg (diluted to 2 ml in 0.9％ sodium chloride solution) was injected via the caudal vein at 15 min before the model was established.At 24 h before operation (T0) and 2,6 and 24 h after operation (T1-3),the mechanical paw withdrawal threshold (MWT) and cumulative pain score were measured.After measurement of the pain threshold at T3,the whole brain was removed for determination of the c-fos expression in neurons in the midbrain periaqueductal gray by immunohistochemistry.Results Compared with group C,the MWT was significantly decreased,cumulative pain scores were increased,and the expression of c-fos in neurons in the midbrain periaqueductal gray was upregulated at T1-3 in I and D groups (P＜0.05).Compared with group I,the MWT was significantly increased,the cumulative pain score was decreased,and the expression of c-fos protein in neurons in the midbrain periaqueductal gray was down-regulated at T1.3 in group D (P＜0.05).Conclusion Dezocine mitigates incisional pain through inhibiting the expression of c-fos in neurons in the midbrain periaqueductal gray of rats.