Abstract:
The present study was performed to determine the effect of intracerebroventricular (ICV) administration of W7, a specific calmodulin inhibitor, on the development of tolerance to antinociceptive effect morphine
administration. This study was carried out on male wistar rats, weighing 200-250 g. Morphine was administered
daily (15 mg/kg for 8 days). The threshold to thermal nociceptive stimuli was measured by tail-flick test. W-7
(0.25, 0.5 and 1 µmol/rat) was injected through ICV. Maximal possible effect percentage (MPE %) was
considered as analgesia index.
Our result showed that chronic morphine exposure induced tolerance to its antinociceptive effect and
administration of W-7 (0.5 and 1 µmol/rat) decreased the development of tolerance to it.
In conclusion these data showed that chronic injection of W-7 inhibited the development of morphine tolerance
which indicates that calmodulin and its dependent pathways may play a role in the morphine tolerance
processes.
