Increased susceptibility to development of anhedonia in rats with chronic peripheral nerve injury: Involvement of sleep deprivation?

The main purpose of the present study was to evaluate whether REM sleep deprivation (RSD) influences the development of anhedonia in rats in a peripheral neuropathy model induced by sciatic nerve constriction injury (CCI). Anhedonia was measured by assessing daily water/sucrose intake. Four groups were assessed: control (CTRL), CCI, RSD, and CCI + RSD (n = 8/group). Intake data were collected at baseline (mean of 3 days), on the 1st and 2nd days after a CCI or SHAM procedure, during 4 days of RSD, and during an additional 10 days (rebound period or equivalent in home-cage rats). Control rats spontaneously and progressively increased sucrose intake, reaching final daily volumes significantly greater than respective initial baseline amounts. RSD promoted an additional and immediate significant increase in sucrose intake during sleep deprivation days. The CCI group did not display a spontaneous, progressive increase in sucrose intake. When CCI was combined with RSD, the increase in sucrose intake induced by RSD was significantly lower than in animals submitted to RSD alone; the (CCI + RSD) group also failed to show a spontaneous and progressive increase in sucrose intake. The present findings indicate that animal model of chronic neuropathy exhibits reduced sucrose ingestion. Accordingly, this anhedonic condition that constitutes to the core manifestation of depressive states did not occur in response to a single episode of total RSD.