Wiley RG, Kline IV, RHLappi DA (2004) Intrathecal galanin-saporin and NPY-saporin reduce nocifensive responses to noxious heat and formalin. Neuroscience 2004 Abstracts 292.15. Society for Neuroscience, San Diego, CA.
Summary: Although the precise circuitry of the dorsal horn underlying nociception is not fully understood, there is evidence that regulation of the excitability of nociceptive projection neurons is influenced/modulated by excitatory interneurons. The present study sought to determine if selectively destroying presumed excitatory interneurons in the superficial dorsal horn would alter nocifensive responses to noxious thermal or chemical stimuli. The strategy chosen was to inject saporin (SAP) conjugates of either galanin (GAL) or neuropeptide Y (NPY) into the lumbar subarachnoid space and then test rats on the hotplate and observe the nocifensive responses to hindpaw formalin injection. After hotplate testing for 2 weeks, staining for c-fos expression in the dorsal horn was performed 2 hrs after hindpaw formalin injection. Lumbar intrathecal injection of 500 ng of either GAL-SAP or NPY-SAP produced no obvious change in appearance, body weight or spontaneous activity of adult male Sprague-Dawley rats. Both toxins reduced responses on the 44 C hotplate but not at 52 C. Nocifensive responses to the 47 C hotplate also were reduced but not as strikingly as at 44 C. Responses to hindpaw formalin were remarkably different. Toxin-injected rats held the injected foot close to the body, off the floor, throughout the 90 minute observation period but otherwise ignored the injected paw. Unlike controls, toxin-injected rats did not shake, lick or bite the injected hindpaw and showed normal exploratory behavior. These results are interpreted as showing that these two toxins likely destroy excitatory interneurons in the superficial dorsal horn resulting in decreased excitability of nociceptive projection neurons, and therefor reduced sensitivity to noxious thermal and chemical stimuli.
Related Products: NPY-SAP (Cat. #IT-28), Galanin-SAP (Cat. #IT-34)