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Nicotine blocks quinpirole-induced behavior in rats: psychiatric implications
Y Tizabi1, R L Copeland, R Brus
1Department of Pharmacology, College of Medicine, Howard University, 520W Street N.W., Washington, DC 20059, USA. ytizabi@howard.edu
Rationale And Objectives:
Because of known and imputed roles of dopaminergic and nicotinic cholinergic systems in a variety of neurological and neuropsychiatric disorders, combined neurochemical and behavioral methods assessments were made to study the intermodulatory roles of these neurochemical systems.
Methods:
Rats were treated daily during postnatal ontogeny with the dopamine D2/D) agonist, quinpirole (QNP) HCl (1.0 mg/kg/day), for the first 3 weeks from birth. This priming process replicated previous findings of behavioral sensitization, manifested as hyperlocomotion, increased paw treading with jumping, and increased yawning.
Results:
All effects were partially or totally blocked by acute treatment with nicotine (0.3 mg/kg, i.p.). The effects of nicotine, in turn, were partially or totally blocked by the nicotinic antagonist, mecamylamine (1.0 mg/kg, i.p.). In concert with these behavioral actions, QNP-primed rats displayed greater binding of [3H]cytisine in midbrain and cerebellum and greater [125I]alpha-bungarotoxin binding in hippocampus and striatum.
Conclusions:
Accordingly, these selective ligands for alpha4beta2 and alpha7 nicotinic receptors, respectively, demonstrate that nicotinic receptors are altered by dopamine D2/D3 agonist treatment of rats with primed dopamine receptors. We propose that nicotinic agonists may have a therapeutic benefit in behavioral disorders brought about by central dopaminergic imbalance.