Normal expression and inflammation-induced changes of Na and Na/K ATPase activity in spinal dorsal horn of the rat

We tested whether that peripheral inflammation induces changes in the spinal dorsal horn ATPase activity. Adult Sprague-Dawley rats were anesthetized (thiobarbital), the left hind paw (inflammation group; n = 15) was immersed in water at 60 °C for 60 s, which induced a local inflammation. A control group (n = 12) was tested with water at room temperature. After 60 min of peripheral inflammation left (LDH) or right lumbar dorsal horn (RDH) were processed for total, Na/K, Na and remanent ATPase activities (nM Pi (mg protein)−1 min−1). In control animals isoenzymatic activities were: Na (31.2%); Na/K (20.6%) and remanent (48.2%) from total ATPase activity. No LDH-RDH asymmetry was found. The inflammation group presented an ipsilateral increase of total ATPase activity in LDH (X ± S.E.M.; 4798.9 ± 601) over the RDH (3982.2 ± 451; Δ + 817; P < 0.05). This is due to an increase in Na ATPase activity (1609.3 ± 297) over RDH (1164.2 ± 166; Δ + 445; P < 0.05). ATPase activities were increased in LDH from inflamed over the control group as follows: total (4798.9 ± 601; Δ + 840; P < 0.05), Na/K (1298.1 ± 301; Δ + 483; P < 0.05) and Na (1609.3 ± 297; Δ + 373; P < 0.05). These increased ATPase activities, induced in a short time, can be considered a functional marker of nociceptive neuronal activity.