Cholecystokinin octapeptide and the D2 antagonist raclopride induce Fos-like immunoreactivity in the shell part of the rat nucleus accumbens via different mechanisms.
Induction of neuronal Fos-like immunoreactivity (IR) in the rat brain by cholecystokinin octapeptide (CCK-8) and the dopamine (DA) D2 receptor antagonist raclopride was demonstrated. In vivo treatment with the CCK-8 (0.01, 0.1 and 1 nmol/rat, i.c.v.) or the D2 antagonist raclopride (0.1, 0.5 and 1 mg/kg, i.p.) alone increased in a dose-dependent way the Fos-like ir profiles in the shell part of the rat nucleus accumbens (AcbSh). Combined treatment with CCK-8 (0.1 nmol/rat) and raclopride (0.5 mg/kg) caused significant additive increases in the Fos-like ir profiles in the AcbSh. In the central caudate-putamen, the medial olfactory tubercle, and the frontal cerebral cortex where either compound alone was weakly active or inactive, the combined treatment with both compounds led to a significant induction of neuronal Fos-like ir profiles. These results suggest that the blockade of D2 and activation of CCK transduction lines can induce Fos-like IR via different mechanisms. They may produce additive effects in AcbSh and synergistic effects in the caudate-putamen and the olfactory tubercle on the induction of neuronal Fos-like IR and thus on long-term regulation of gene expression in the striatum.
Li
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Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
Chadi
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Fuxe
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D000818:Animals; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009714:Nucleus Accumbens / Q000187:drug effects*; D016760:Proto-Oncogene Proteins c-fos / Q000276:immunology*; D020891:Raclopride; D051381:Rats; D017207:Rats, Sprague-Dawley; D012457:Salicylamides / Q000494:pharmacology*; D012844:Sincalide / Q000494:pharmacology*
D018492:Dopamine Antagonists; D016760:Proto-Oncogene Proteins c-fos; D012457:Salicylamides; D020891:Raclopride; D012844:Sincalide