Continuous assay of proteases using a microtiter plate fluorescence reader

The present study was designed to determine if spinal calcium channels, calmodulin, and calcium/calmodulin-dependent protein kinase II were involved in the production of antinociception induced by cold water swimming stress (CWSS). The effects of intrathecal (i.t.) injection of nimodipine, omega-conotoxin GVIA, calmidazolium, or (S)-5-isoquinolinesulfonic acid, 4-2-(5-isoquinolinyl-sulfonyl)methylamino]-3-oxo-3-(4-phenyl-1-piperaz inyl)-propyl]phenyl ester (KN-62) on CWSS-induced antinociception were studied in ICR mice. The antinociception was assessed by the tail-flick test. CWSS produced inhibition of the tail-flick response. Various doses of nimodipine (10-40 ng), omega-conotoxin GVIA (5-40 ng), calmidazolium (10-40 ng), or KN-62 (5-40 ng) injected i.t. alone did not show any antinociceptive effect in the tail-flick test. I.t. pretreatment with omega-conotoxin GVIA, calmidazolium, or KN-62 dose dependently attenuated the CWSS-induced inhibition of the tail-flick response. However, i.t. pretreatment with nimodipine did not affect the inhibition of the tail-flick response induced by CWSS. Our results suggest that spinal N-type calcium channel, calmodulin and calcium/calmodulin-dependent protein kinase II may be involved in the production of antinociception induced by CWSS. On the other hand, CWSS-induced antinociception appears not to be mediated via the spinal L-type calcium channel.