Intrathecal levobupivacaine downregulates substance P expression in the distal cerebrospinal fluid contacting neuron for formalin-induced inflammatory pain in rats / 中国药理学通报

ABSTRACT

Aim To investigate the effects of intrathecal levobupivacaine(LB)on substance P(SP)expression in spinal dorsal horn(L4~5)and the distal cerebrospinal fluid contacting neuron(dCSF-CN)in a rat model of formalin induced inflammatory pain.Methods Twelve male Sprague-Dawley rats(290~310 g,Grade SPF)were randomly divided into 2 groups with 6 in each.Rats were anesthetized with sodium pentobarbital(40 mg?kg-1,ip)and then fixed in the stereotaxic instrument.A 3 ?l volume of 30% CB-HRP to trace dCSF-CN was injected into one of the rats'lateral ventricles.The animals kept alive,forty eight hours later artificial cerebrospinal fluid(ACSF)10 ?l and 0.5% LB 10 ?l(diluted with ACSF)were intrathecally injected in group ACSF and group LB respectively.Inflammatory pain was induced by formalin injection into left hind paw.Then nociception of the animals was assessed behaviorally with the formalin test.Two hours after formalin administration,rats were sacrificed with deeply anesthesia and transcardially perfused.L4~5 segments of spinal cord were removed for immunohistochemical SP-labeling.Brainstem segments containing dCSF-CN were removed for SP/CB-HRP dual-labeling with immunohistochemical procedures and colloidal gold immunoelectronmicroscopy.Results LB significantly reduced paw licking time in the formalin test(P 0.05vsbaseline,P