Morphological Studyies On The Expression Changes Of The Prostatic Acid Phosphatase In The Spinal Dorsal Horn And Dorsal Root Ganglion In The Chronic Pain State Of The Rat

Chronic pain as a serious hazard to human physical and mental healthdisease has draw great attention in the world. As for the pathological mechanismsof the chronic pain is very complicated, there is still no satisfactory treatment forsuch disease now, especially no more effective drugs are available to treat chronicpain explicitly. Recent animal behavior studies have shown that prostatic acidphosphatase (PAP) has a good analgesic effect in animal models of neuropathicpain and inflammatory pain. But in the chronic pain state the expression changesof PAP in the spinal dorsal horn and dorsal root ganglion have not been reportedin systemic study.As a possible and potential analgesic in the future, we usedimmunohistochemical technique in our research. We studied the distribution ofPAP in the primary afferents and spinal cord, and explored the possibleneurological mechanisms of PAP analgesic effect. The main results are asfollows: 1. The distribution of the PAP in rat dorsal root ganglion and spinal dorsalhorn.The immunohistochemical staining showed that the PAP immunoreactiveproducts were mainly concentrated in the membrane and perinuclear region ofsmall-to medium-sized neurons in dorsal root ganglion (DRG), as well as in thinmyelinated and unmyelinated primary afferent terminals in laminae II of spinaldorsal horn (SDH).2. The neurochemical phenotype of PAP-positive neurons and primaryafferent terminalsImmunofluorescence triple labeling staining showed that PAP widely coexistwith non-peptidergic isolectin B4(IB4)-positive neurons and their terminals; afew PAP-positive neurons and their terminals expressed the neurotransmitterssubstance P (SP) and calcitonin gene-related peptide (CGRP); some PAP positiveprimary afferent terminals overlaped with protein kinase Cγ (PKCγ)-positiveneurons in inner laminae II of spinal cord. Immunofluorescence double labelingstaining showed that adenosine A1receptor (A1R) was mainly expressed inlarge-sized DRG neurons, no PAP-positive and A1R-positve double-labeledneuron was found in DRG.3. The expression of PAP in the SDH and DRG of the rat in differentchronic pain animal modelsThe immunohistochemical staining showed that, the expression of PAP wereboth decreased in ipsilateral DRG and SDH of the neuropathic pain animalmodels induced by nerve injury and CIBP animal models at different degrees,which were corresponding with the extent of nerve injury. However, there was nosignificantly decrease in PAP expression in DRG and SDH of inflammation painanimal model. Our results indicated that PAP was principally located in small-tomedium-sized nociceptive neurons in the DRG, and in primary afferent terminalsin laminae II of spinal cord; PAP was mainly expressed in non-peptidergicnociceptive neurons and their terminals. The expression of PAP in DRG and SDHwere markedly decreased in neuropathic pain and CIBP models, but nosignificant expression changes of PAP in the inflammatory pain animal modelwas observed. These results suggest that PAP was mainly through thenon-peptidergic nociceptive primary afferent influence pain informationtransmission; Peripheral nerve damage may affect the endogenous synthesis ofPAP and its transport along the primary afferent to the spinal cord.