Rapid eye movement (REM) sleep deprivation has been shown to decrease pain
threshold after various pain stimuli. Down regulatory antagonist modulator
(DREAM) is a transcriptional repressor of prodynorphin gene. This study evaluates
the effect on DREAM in relation to REM sleep deprivation, formalin induced pain or
combination of both; and its relationship to the formalin induced pain behavioural
responses. Male Sprague Dawley rats (250-300 g) were divided into four major
treatments; free moving control (n=36), REM sleep deprivation (n=36), tank control
(n=36) and sleep recovery (n=36). REM sleep deprivation was elicited for 72 hours
using the inverted flower pot technique. Each group was further divided into two
groups which consisted of rats that were either not or subjected to 2.5% formalin
subcutaneous injection. Food consumption and body weight gain were measured
before and after the treatments. The formalin induced pain behavioural responses
were recorded for one hour for rats that subjected to formalin injection. The
ventrobasal thalamic complex of brain (VB) were removed from each group for
immunohistochemistry (n=6), Western blot (n=6) and real-time PCR analysis (n=6)
separately. The ‘inverted flower’ pot technique was confirmed to induce REM sleep
deprivation in the REM sleep deprived and sleep recovered rats by the classic pattern
of hyperphagia with converse loss of body weight. There is a marked hypoalgesia
demonstrated in the second phase of formalin induced pain in the REM sleep
deprived rats. REM sleep deprivation per se did induce morphological change and
reduced the number of DREAM positive neurons (DPN) bilaterally