The role of spinal inhibitory neuroreceptors in the antihyperalgesic effect of warm water immersion therapy.
OBJECTIVE
Warm water immersion therapy (WWIT) has been widely used in the treatment of various clinical conditions, with analgesic and anti-inflammatory effects. However, its mechanism of action has not been fully investigated. The present study analyzed the role of spinal inhibitory neuroreceptors in the antihyperalgesic effect of WWIT in an experimental model of inflammatory pain.


METHODS
Mice were injected with complete Freund's adjuvant (CFA; intraplantar [i.pl.]). Paw withdrawal frequency to mechanical stimuli (von Frey test) was used to determine: (1) the effect of intrathecal (i.t.) preadministration of naloxone (a non-selective opioid receptor antagonist; 5 µg/5 µl), (2); AM281 (a selective cannabinoid receptor type 1 [CB1] antagonist; 2 µg/5 µl), (3); and 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; a selective adenosine A1 receptor antagonist; 10 nmol/5 µl), on the antihyperalgesic (pain-relieving) effect of WWIT against CFA-induced hyperalgesia.


RESULTS
Intrathecal naloxone, AM281, and DPCPX significantly prevented the antihyperalgesic effect of WWIT. This study suggests the involvement of spinal (central) receptors in the antihyperalgesic effect of WWIT in a model of inflammatory pain.


CONCLUSIONS
Taken together, these results suggest that opioid, CB1, and A1 spinal receptors might contribute to the pain-relieving effect of WWIT.
['Madeira|Fernanda|F|', 'Brito|Rômulo Nolasco de|RN|', 'Emer|Aline A|AA|', 'Batisti|Ana Paula|AP|', 'Turnes|Bruna Lenfers|BL|', 'Salgado|Afonso Shiguemi Inoue|ASI|', 'Cidral-Filho|Francisco José|FJ|', 'Mazzardo-Martins|Leidiane|L|', 'Martins|Daniel Fernandes|DF|']
D000818:Animals D005620:Freund's Adjuvant D006930:Hyperalgesia D007101:Immersion D007249:Inflammation D051379:Mice D009270:Naloxone D009292:Narcotic Antagonists D059408:Pain Management D011984:Sensory Receptor Cells D014867:Water D014970:Xanthines
Opioid Cannabinoid Adenosine Physical therapy Rehabilitation