Effect Of Peripheral Injury On Substance P Immunoreactivity In Spinal Cord And Localization Of Mel_1a Receptor In Spinal Cord

1. Substance P is a neuropeptide prominently expressed in small primary sensory afferents that is involved in the modulation of pain-related information in the spinal dorsal horn.Using immunohistochemistry and optical densitometry, substance P was investigated in Bufo bufo gargarizans spinal cord after sciatic nerve transection. In control animals, there was a high density of substance P fibers in the Lissauer's tract. No substance P label was found in any cell bodies. After axotomy, substance P immunoreactive fibers decreased in the Lissauer's tract on the same side of the lesion. The changes were observed at 3 days(0.84±0.02) following axonal injury and persisted at 8(0.50±0.03) and 15 days(0.45±0.04). At 20 days(0.60±0.04) and 30 days(0.69±0.03), there was no significant difference between the axotomized side and the control one, thus indicating a recovery of the substance P expression. These results indicate that Bufo bufo gargarizans may be used as a model to study the effects of peripheral axotomy, contributing to elucidate the Substance P actions in the pain neuropath.2. Melatonin is a kind of neuroendocrine hormone, which regulates the functions of Central Nervous System(CNS) by its receptors.In order to learn more about the regulatory function of melatonin to different lamina of spinal cord, we localized and characterized Mel1a receptor in the spinal cord of Gecko swinhoniss by immunofluorescence. Studies demonstrated the presence of Mel1a receptor located mainly in laminae I-V, lamina VII and lamina X of the spinal cord. The positive cells were small and mostly round in laminae I-V and X, while in lamina VII the positive cells were large and the shapes in them were cycloidal, triangle and elliptical. The statistical results showed that the positive cells in lamina VI(22.36±2.36/mm2), lamina VIII(24.07±2.05 /mm2) and lamina IX(30.56±2.87/mm2) were evidently lesser than those in laminae I-V(450.25±9.65/mm2)(P<0.05); The positive cells in lamina VII(476.90±11.26/mm2) and lamina X(480.64±12.98/mm2) did not have significant difference with those in laminae I-V(P>0.05). These results indicate that melatonin in spinal cord may play a role in the movement of reptile by its receptors besides the modulatory effect of melatonin on the mechanisms of sensory transmission of the spinal cord.