Blockade of peripheral and spinal Na+/H+ exchanger increases formalin-induced long-lasting mechanical allodynia and hyperalgesia in rats.
The Na(+)/H(+) exchanger (NHE) is involved in the regulation of intracellular pH and volume by mediating the electroneutral transport of H(+) against an influx of Na(+) ions. Since NHE1 regulates pH in neurons and astrocytes and it is expressed in nociceptive nerve fibers, it is likely that NHE may modulate neuronal excitability and pain transmission. The purpose of this study was to assess the participation of peripheral and spinal NHE in the secondary allodynia/hyperalgesia induced by formalin. In addition, we determined whether formalin injection modifies the expression of NHE1 in lumbar dorsal root ganglia (DRG) and dorsal spinal cord. Subcutaneous injection of 0.5% formalin into the dorsal surface of the hind paw produced acute nociceptive behaviors (flinching and licking/lifting) followed by long-lasting bilateral secondary mechanical allodynia/hyperalgesia. Peripheral and intrathecal pre-treatment (-10min) with selective NHE inhibitors 5-(N,N-dimethyl)amiloride hydrochloride (DMA, 0.3-30μM), 5-(N-ethyl-N-isopropyl)amiloride (EIPA, 0.3-30μM) and [1-(quinolin-5-yl)-5-cyclopropyl-1H-pyrazole-4-carbonyl] guanidine dihydrochloride (zoniporide, 0.03-3μM) significantly increased 0.5% formalin-induced bilateral long-lasting secondary allodynia/hyperalgesia. Contrariwise, local peripheral or intrathecal post-treatment (day 6 postinjection) with these NHE inhibitors did not affect formalin-induced nociceptive behaviors. Formalin injection reduced NHE1 expression in ipsilateral and contralateral spinal dorsal horns from day 1 to 12. In addition, formalin diminished NHE1 protein expression in DRG at day 12. These results suggest that NHE1 plays a role in pain processing at peripheral and spinal levels in formalin-induced long-lasting nociceptive behaviors. Additionally, these results suggest that proteins involved in pH regulation could be targets for the development of new analgesic drugs.
Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados, Sede Sur, México, D.F., Mexico.
Gabriela
G
Castañeda-Corral
Héctor I
HI
Rocha-González
Claudia I
CI
Araiza-Saldaña
Guadalupe C
GC
Vidal-Cantú
Juan
J
Miguel Jiménez-Andrade
Janet
J
Murbartián
Vinicio
V
Granados-Soto
D000584:Amiloride / Q000008:administration & dosage / Q000031:analogs & derivatives; D000818:Animals; D005260:Female; D006930:Hyperalgesia / Q000139:chemically induced / Q000201:enzymology*; D007278:Injections, Spinal; D010147:Pain Measurement / Q000187:drug effects / Q000379:methods*; D010525:Peripheral Nerves / Q000187:drug effects / Q000201:enzymology*; D010812:Physical Stimulation / Q000009:adverse effects; D051381:Rats; D017208:Rats, Wistar; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors* / Q000096:biosynthesis* / Q000502:physiology; D013116:Spinal Cord / Q000187:drug effects / Q000201:enzymology*
C452850:Slc9a1 protein, rat; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; C039614:ethylisopropylamiloride