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Enhanced morphine analgeisa after spinal dermorphin-saporin

Miller SA, Lappi DA, Wiley RG (2002) Enhanced morphine analgeisa after spinal dermorphin-saporin. Neuroscience 2002 Abstracts 218.1. Society for Neuroscience, Orlando, FL.

Summary: Dermorphin-saporin (derm-sap) is a neuropeptide toxin conjugate which is selective for neurons expressing the mu-opiate receptor (MOR). The dermorphin moiety of the conjugate binds MOR which is then internalized by the neuron, carrying the toxin with it. The saproin moiety inactivates ribosomes resulting in cell death. In the present study we sought to determine the effect of destroying MOR expressing neurons in Lamina II of the spinal cord dorsal horn on baseline thermal pain sensitivity and response to systemic morphine analgesia. 456 ng derm-sap (n=8) and vehicle (n=8) were injected into the lumbar CSF of adult male Sprague Dawley rats using a subarachnoid catheter inserted through the atlanto-occipital membrane and passed cadually to the level of the lumbar enlargement. 10 minutes following toxin injection, the catheters were withdrawn and the animals allowed to recover. When tested on a hotplate at 52C and on tail-flick assay, toxin rats did not differ from rats injected with vehicle. However, the dose-response curves for subcutaneous morphine were significantly shifted to the left (increased potency) in the toxin treated rats when compared with vehicle controls. Histological analysis of multiple dorsal root ganglia failed to reveal evidence of any primary afferent cell loss. We interpreted these findings to indicate that the neurons destroyed by derm-sap are lamina II MOR expressing neurons and play a role in morphine analgesia at high stimulus intensities.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

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