Differential activation of accumbens shell and core dopamine by sucrose reinforcement with nose poking and with lever pressing.
In order to investigate the role of modus operandi in the changes of nucleus accumbens (NAc) dopamine (DA) transmission in sucrose reinforcement, extracellular DA was monitored by microdialysis in the NAc shell and core of rats trained on a fixed-ratio 1 schedule to respond for sucrose pellets by nose poking and lever pressing respectively. After training, rats were tested on three different sessions: sucrose reinforcement, extinction and passive sucrose presentation. In rats responding by nose poking dialysate DA increased in the shell but not in the core under reinforced as well as under extinction sessions. In contrast, in rats responding by lever pressing dialysate DA increased both in the accumbens shell and core under reinforced and extinction sessions. Response non-contingent sucrose presentation increased dialysate DA in the shell and core of rats trained to respond for sucrose by nose poking as well as in those trained by lever pressing. In rats trained to respond for sucrose by nose poking on a FR5 schedule dialysate DA also increased selectively in the NAc shell during reinforced responding and in both the shell and core under passive sucrose presentation. These findings, while provide an explanation for the discrepancies existing in the literature over the responsiveness of shell and core DA in rats responding for food, are consistent with the notion that NAc shell and core DA encode different aspects of reinforcement.
Department of Biomedical Sciences, University of Cagliari, Via Ospedale 72, 09124 Cagliari, Italy. Electronic address: bassareo@unica.it.
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Bassareo
Department of Biomedical Sciences, University of Cagliari, Via Ospedale 72, 09124 Cagliari, Italy.
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Cucca
Department of Biomedical Sciences, University of Cagliari, Via Ospedale 72, 09124 Cagliari, Italy.
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Frau
Department of Biomedical Sciences, University of Cagliari, Via Ospedale 72, 09124 Cagliari, Italy; CNR Institute of Neuroscience, Cagliari Section, Via Ospedale 72, 09124 Cagliari, Italy. Electronic address: dichiara@unica.it.
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Di Chiara
D000818:Animals; D002408:Catheters, Indwelling; D019422:Dietary Sucrose / Q000008:administration & dosage; D004298:Dopamine / Q000378:metabolism*; D005108:Extinction, Psychological / Q000502:physiology; D005110:Extracellular Space / Q000378:metabolism; D005552:Forelimb / Q000502:physiology*; D008297:Male; D017551:Microdialysis; D009043:Motor Activity / Q000502:physiology*; D009666:Nose / Q000502:physiology*; D009714:Nucleus Accumbens / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D012054:Reinforcement, Psychology
D019422:Dietary Sucrose; D004298:Dopamine
Accumbens; Core; Dopamine; Lever pressing; Nose poking; Shell; Sucrose