Local pentoxifylline administration decreases the formalin induced Fos expression in rat spinal cord

Pro-inflammatory cytokines play a key role in the inflammatory response and contributing to producing local hyperalgesia. It is known that pentoxifylline inhibits inflammatory cytokine production. Therefore, the aim of this study was to find out, using a behavioural test and neuronal Fos expression, if this drug had some antinociceptive effect decreasing nociresponsive neuron activation in the spinal cord after nociceptive inflammation (injection of formalin in the hind paw). Our data showed that formalin induced a great number of Fos-positive neurons in the dorsal horn of the lumbar spinal cord mainly in the ipsilateral I and II laminae. The local pre-treatment with pentoxifylline before the formalin injection, decreased the nociceptive response in the formalin test and the number of Fos positive neurons in the spinal cord. This finding suggests that pentoxifylline is involved in decreasing the activation of nociresponsive neurons in the spinal cord playing a role in local anti-nociception