Journal
PHARMACOLOGY BIOCHEMISTRY AND BEHAVIOR
Volume 86, Issue 1, Pages 162-168Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.pbb.2006.12.020
Keywords
WIN 55,212-2; elevated plus maze; Western blot; tyrosine hydroxylase; norepinephrine; CB1 receptor; microdialysis
Funding
- NATIONAL INSTITUTE ON DRUG ABUSE [R01DA020129] Funding Source: NIH RePORTER
- NIDA NIH HHS [R01 DA020129, R01 DA020129-01] Funding Source: Medline
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The present study examined the impact of repeated administration of a synthetic cannabinoid agonist, WIN 55,212-2 on the coeruleo-cortical pathway, a circuit implicated in anxiety. Male Sprague-Dawley rats received repeated systemic injections of WIN 55,212-2 (3.0 mg/kg). A separate group of rats received repeated WIN 55,212-2 injections followed by a period of abstinence. Control animals received vehicle injections. Ninety minutes following the last injection on day 8, anxiety-related behavior was assessed using the elevated plus maze. The abstinent group was tested after another 8 days. Following behavioral testing, brain tissue was extracted from the locus coeruleus (LC) and probed for tyrosine hydroxylase (TH) expression. In a separate group of animals, in vivo microdialysis was used to monitor extracellular norepinephrine efflux in the frontal cortex following repeated WIN 55,212-2 administration and following a period of abstinence. Repeated administration of WIN 55,212-2 evoked an anxiogenic-like response that was accompanied by an increase in TH protein expression in the LC. A similar neurochemical profile was observed using in vivo microdialysis where an augmented increase in cortical norepinephrine efflux was identified in response to a systemic injection of WIN 55,212-2 on day 8. Anxiety-like behavior, catecholamine synthesizing enzyme levels and NE efflux returned to control values after 8 days of abstinence. The present findings indicate that repeated administration of a synthetic cannabinoid receptor agonist induces transient anxiety-like behaviors that correlate with increases in catecholamine synthesizing enzyme expression in the LC and augmented norepinephrine efflux in response to a challenge injection of WIN 55,212-2. (c) 2007 Elsevier Inc. All rights reserved.
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