Planta medica
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Our researches in recent years have shown that oxysophoridine (OSR), an alkaloid extracted from Siphocampylus verticillatus, presents antinociception through systemic and intracerebroventricular (icv) administration, and that OSR can also increase the GABA-immunopositive cells number in the central nervous system in rats. The purpose of the present study was to investigate the antinociception produced by OSR administered spinally, the interaction between OSR and GABAA receptor (GABAAR) agonists or antagonists on acute thermal nociceptive models (tail-flick test), and the possible alterations on the mRNA and protein expression of GABAAα1 receptors in the spinal cord. ICR mice were tested for their tail withdrawal response to thermal stimulation (tail-flick test). ⋯ OSR (0.25 mg/site, i. t.) can increase the expression of mRNA and protein of the GABAAα1 receptor in the spinal cord (L5-L6). The results reveal that i. t. administered OSR presents effective antinociception whose action is mainly located in the spinal cord. The antinociception of OSR results from the activation of the GABAA receptor and from the regulation of the GABAAα1 receptor-mediated neurotransmission.