Peripheral withdrawal recruits distinct central nuclei in morphine-dependent rats

This study examined if brain pathways in morphine-dependent rats are activa ted by opioid withdrawal precipitated outside the central nervous system. W ithdrawal precipitated with a peripherally acting quaternary opioid antagon ist (naloxone methiodide) increased Fos expression but caused a more restri cted pattern of neuronal activation than systemic withdrawal (precipitated with naloxone which enters the brain). There was no effect on locus coerule us and significantly smaller increases in Fos neurons were produced in most other areas. However in the ventrolateral medulla (A1/C1 catecholamine neu rons), nucleus of the solitary tract (A2/C2 catecholamine neurons), lateral parabrachial nucleus, supramamillary nucleus, bed nucleus of the stria ter minalis. accumbens core and medial prefrontal cortex no differences in the withdrawal treatments were detected. We have shown that peripheral opioid w ithdrawal can affect central nervous system pathways. Crown Copyright (C) 2 001 Published by Elsevier Science Ltd. All rights reserved.