Progesterone Prevents Allodynia After Experimental Spinal Cord Injury

Progesterone Prevents Nerve Injury-Induced Allodynia and Spinal NMDA Receptor Upregulation in Rats

“…These findings extend our previous observations [29] demonstrating that progesterone favors a molecular environment at the dorsal horn level that contributes to prevent allodynia after spinal cord injury.…”

“…As in other models of neuropathic pain [8, 29,53], the single ligature constriction of the sciatic nerve induced a dramatic increase in the number of NR1-and pNR1-immunopositive profiles in all the spinal cord regions evaluated (P < 0.001 vs C for both markers in the three regions; see SLNCi in Figure 2A-D). While the contralateral side remained unaffected (P > 0.05 vs C for both markers in the three regions), a significant increase in the total number of NR1-IR profiles was observed in the ipsilateral dorsal horn of animals subjected to the peripheral nerve injury (78% in laminae I-II, 67% in laminae III-IV, 53% in laminae V-VI), when compared with control animals.…”

“…A growing amount of literature supports the notion that neuroactive steroids display key regulatory effects in the control of pain and might represent a potential therapeutic approach for the treatment of neuropathic pain and the prevention of morphine tolerance [19][20][21][22][23][24][25][26][27][28][29][30]. Progesterone, in particular, mediates gestational antinociception [31], potentially contributes to sex-related differences in pain [31][32][33] and reduces pain sensitivity in intact rats [34].…”

“…More recently, we have shown that progesterone prevents allodynia after spinal cord injury and modulates the expression of several pain-related molecules with crucial roles in nociceptive processing at the spinal level [29].…”

Pain Perception during Menstrual Cycle

“…Moreover, both female hormones modulate mediators such as cytokines in the rat temporomandibular joint (TMJ) [14]. In analogy with estrogens, progesterone showed both pronociceptive and antinociceptive effect, given that it was able to reduce allodynia in neuropathic pain after spinal cord injury [15], but increased hyperalgesia in male and ovariectomized female rats [16]. Despite these interactions between gonadal hormones, brain functions, and pain processing supporting the different expression of pain symptoms between sexes [2], inconsistencies exist regarding the reliability of pain perception fluctuation and which estrous phases are associated with greater nociception.…”