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6249918 
Journal Article 
Chromaffin cell transplant in spinal cord reduces secondary allodynia induced by formalin in the rat. Role of opioid receptors and α₂-adrenoceptors 
Ambriz-Tututi, M; Sánchez-González, V; Drucker-Colín, R 
2011 
1 
European Journal of Pharmacology
ISSN: 0014-2999
EISSN: 1879-0712 
668 
1-2 
147-154 
English 
21741968 
In the present study, the effect of chromaffin cell transplant in the spinal cord was evaluated on formalin-induced mechanical secondary allodynia in the rat. Chromaffin cells were transplanted into the lumbar subarachnoid space before or after formalin injection. Subcutaneous formalin injection (50 μl, 1%) produced long-lasting secondary allodynia in the ipsilateral and contralateral hind paws. Once secondary allodynia was established, treatment with chromaffin cells produced a significant reduction in the nociceptive behavior in both hind paws. The antiallodynic effect was time-dependent since it was observed 15 days after chromaffin cell transplants but not before. On the other hand, pre-treatment with chromaffin cells prevented the expression of secondary allodynia in both hind paws in the rat. Antiallodynic effect of chromaffin cells was reverted with the non-selective opioid receptor antagonist naltrexone and the non-selective α(2)-adrenoceptor antagonist rauwolscine. Clusters of viable chromaffin cells labeled with anti-tyrosine hydroxylase antibodies were observed in the retrieved transplants 15 days after transplant. These results establish the analgesic efficacy of intrathecal chromaffin cells on formalin-induced secondary allodynia. Our data suggest that chromaffin cells release neuroactive substances including opioid peptides and adrenergic amines that reduce secondary allodynia in rats through activation of their receptors.