Wiley RG, Kline IV RH, Lemons LL (2009) Role of galanin receptor-expressing dorsal horn neurons in nocifensive reflex responses to heat. Neuroscience 2009 Abstracts 170.17/X19. Society for Neuroscience, Chicago, IL.
Summary: Spinal intrathecal (i.t.) galanin has been reported to be antinociceptive in some situations. Using lumbar i.t injections of galanin, coupled to the ribosomal inactivating peptide, saporin, to selectively destroy spinal dorsal horn cells that express galanin receptors, we sought to determine the role of galanin receptor-expressing dorsal horn neurons in reflex nocifensive hotplate behavior. Rats were injected into lumbar CSF with either 500 ng or 750 ng Gal-sap or saline, then tested over several weeks on the hotplate at 44o, 47o and 52oC. Gal-sap increased hindpaw withdrawal latencies only to 44oC and decreased the amount of responding on both 44o and 47oC hotplates. Morphine (5 mg/kg, s.c.) twenty minutes before 44°C hotplate testing slightly increased initial response latency and significantly decreased responding of the control rats. The antinociceptive effect of morphine in the Gal-sap rats was approximately additive with the antinociceptive effect of Gal-sap. Mustard oil applied to the dorsal hindpaws significantly increased responding on the 44°C hotplate in control rats, but produced less of an increase in Gal-sap rats. Topical capsaicin to hindpaw plantar skin reduced control, but not Gal-sap, responses on the 44°C hotplate. These results suggest a role for galanin receptor-expressing dorsal horn neurons in modulation of nociception that is unique, different from several other types of dorsal horn neurons and suggests a strategy for augmenting opiate drug effect.
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