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. Author manuscript; available in PMC: 2008 Jan 5.
Published in final edited form as: Neuroscience. 2006 Oct 19;144(1):247–262. doi: 10.1016/j.neuroscience.2006.08.078

Figure 3.

Figure 3

Intermittent morphine age dependently alters mechanical nociception in infant and young rats. Morphine was administered bid from experimental day 1–3, and once on experimental day 4. Baseline mechanical thresholds were collected in the morning immediately prior to the first dose of morphine, and at 1 and 4 hours post-morphine as indicated. Tolerance develops by day 4 only in infant rats administered the higher dose of morphine. A progressive decrease in baseline mechanical thresholds (allodynia) across subsequent days of morphine exposure is only observed in young rats. Withdrawal associated allodynia is seen at both ages. Data is average ± SEM (n=10−11/group in P7 rats, n=5−6/group in P21 rats). α p<0.05 compared to time matched saline injected. *p<0.05 compared to baseline from time matched saline injected animals. +p<0.05 from analgesia observed in the same animals at 1 hours post-morphine on day 1.