The Journal of Neuroscience, August 15, 1998, 18(16):6492-6500
Electrical Stimulation of the Prefrontal Cortex Increases
Cholecystokinin, Glutamate, and Dopamine Release in the Nucleus
Accumbens: an In Vivo Microdialysis Study in Freely Moving
Rats
Zhi-Bing
You1,
Thomas
M.
Tzschentke1,
Ernst
Brodin2, and
Roy A.
Wise1
1 Center for Studies in Behavioral Neurobiology,
Department of Psychology, Concordia University, Montreal, Quebec,
Canada H3G 1M8, and 2 Department of Physiology and
Pharmacology, Karolinska Institute, S-17177, Stockholm, Sweden
In vivo microdialysis, radioimmunoassay, and HPLC
with electrochemical or fluorometric detection were used to investigate the release of cholecystokinin (CCK), glutamate (Glu), and dopamine (DA) in nucleus accumbens septi (NAS) as a function of ipsilateral electrical stimulation of medial prefrontal cortex (mPFC). CCK was
progressively elevated by mPFC stimulation at 50-200 Hz.
Stimulation-induced CCK release was intensity-dependent at 250-700
µA. NAS Glu and DA levels were each elevated by stimulation at
25-400 Hz; the dopamine metabolites DOPAC and homovanillic acid were
increased by stimulation at 100-400 Hz. When rats were trained to
lever press for mPFC stimulation, the stimulation induced
similar elevations of each of the three transmitters to
those seen with experimenter-administered stimulation. Perfusion of 1 mM kynurenic acid (Kyn) into either the ventral
tegmental area (VTA) or NAS blocked lever pressing for mPFC
stimulation. VTA, but not NAS, perfusion of Kyn significantly attenuated the increases in NAS DA levels induced by mPFC
stimulation. Kyn did not affect NAS CCK or Glu levels when perfused
into either the VTA or NAS. The present results are consistent with
histochemical evidence and provide the first in vivo
evidence for the existence of a releasable pool of CCK in the NAS
originating from the mPFC. Although dopamine is the transmitter most
closely linked to reward function, it was CCK that showed
frequency-dependent differences in release corresponding most closely
to rewarding efficacy of the stimulation. Although not essential for
the reward signal itself, coreleased CCK may modulate the impact of the
glutamatergic action in this behavior.
Key words:
cholecystokinin; amino acids; dopamine; microdialysis; prefrontal cortex; nucleus accumbens; brain stimulation reward; rat
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