The Effects Of Sensory Neuron-Specific Receptor On The Modulation Of Nociceptive Transmission

Sensory neuron-specific receptor is uniquely located in the small diameter neurons in dorsal root ganglia (DRG) and trigeminal ganglia (TG). As these neurons are the primary neuron of the nociceptive signal pathway, it is possible that the physiological effect of SNSR is to modulate the transfer of nociceptive signal. We first examined the effects of i.t. (intrathecal) administration of SNSR agonists, Bovine adrenal medulla 8-22 (BAM8-22) and Tyr6-γ2-MSH-6-12 on nociceptive responses and the spinal c-Fos immunoreactivity in the formalin test. Then we determined the effect of i.t. pretreatment with these two agonists in N-methyl-Dg-aspartic acid (NMDA) evoked hyperalgesia. The results showed that both pretreatment with BAM8-22 or post-treatment with BAM8-22 or MSH inhibited the pain response and neuronal Fos-like immunoreactivity in spinal dorsal horn. I.t. pretreatment with these two agonists also suppressed NMDA-evoked hyperalgesia. These results indicated that activation of SNSR can inhibit the transfer of nociceptive signal at spinal level, and this anti-nociceptive effect might take place by affect the activity of NMDA receptors.