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Chronic treatment with Δ‐9‐tetrahydrocannabinol alters the structure of neurons in the nucleus accumbens shell and medial prefrontal cortex of rats
Author(s) -
Kolb Bryan,
Gorny Grazyna,
Limebeer Cheryl L.,
Parker Linda A.
Publication year - 2006
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.20313
Subject(s) - nucleus accumbens , prefrontal cortex , striatum , delta 9 tetrahydrocannabinol , chemistry , hippocampus , cortex (anatomy) , neuroscience , medicine , amphetamine , pharmacology , endocrinology , anesthesia , cannabinoid , psychology , central nervous system , dopamine , receptor , cognition
The potential of repeated exposure to Δ 9 ‐tetrahydrocannabinol (Δ 9 ‐THC) to produce long‐lasting changes in synaptic connections in a manner similar to other drugs of abuse was evaluated in Sprague‐Dawley rats. For 12 days, rats received two i.p. injections per day (8 h apart) of vehicle, a low dose of Δ 9 ‐THC (0.5 mg/kg), or escalating doses of Δ 9 ‐THC (0.5–4.0 mg/kg). Thirty days later, they were evaluated for sensitized locomotor activity (during the night cycle) for 60 min on each of three trials. Using a within‐groups design, rats were tested following an injection of vehicle, 0.5 mg/kg Δ 9 ‐THC or 2.0 mg/kg Δ 9 ‐THC. The rats showed no evidence of sensitized locomotor activity in any group. Twenty‐four hours after the final sensitization test, their brains were removed and then processed for Golgi‐Cox staining. Prior exposure to Δ 9 ‐THC (both the low dose and the escalating doses) increased the length of the dendrites as well as the number of dendritic branches in the shell of the nucleus accumbens and in the medial prefrontal cortex, but not in the hippocampus, striatum, orbital frontal cortex, parietal cortex, or occipital cortex. These results are similar to those evident in brains of rats sensitized to amphetamine, and support previous findings that cannabinoids promote DA activity in the mesolimbic DA system. Synapse 60:429–436, 2006. © 2006 Wiley‐Liss, Inc.