Relationship between limbic and cortical 5-HT neurotransmission and acquisition and reversal learning in a go/no-go task in rats.
BACKGROUND
Specific brain structures have been suggested to be involved in impulsive responding assessed by a variety of operant tasks. Central serotonin (5-HT) function has also been widely implicated in impulsivity; however, little research has addressed the regional aspect of 5-HT roles in different impulsive indices of task performance.


OBJECTIVE
We analyzed the relationships between acquisition and reversal learning in a go/no-go task as different behavioral measures of impulsivity and focal concentrations of 5-HT and its metabolites in the brain.


METHODS
Rats administered with parachloroamphetamine (PCA) and vehicle were tested in both acquisition and reversal phases in a go/no-go visual discrimination task. Neurochemical analysis was performed to determine 5-HT concentrations in micropunched brain tissues.


RESULTS
PCA administration induced regionally 5-HT depletion in the brain and impaired learning performance in both tests. For both tests, significant negative correlations between learning performance and 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) concentrations were observed in the medial prefrontal cortex (mPFC) and amygdala (Amyg). In contrast, significant negative correlations between learning performance and 5-HT and 5-HIAA concentrations were observed for the orbitofrontal cortex (OFC) exclusively in the reversal learning phase.


CONCLUSIONS
The present data indicate that 5-HT neurotransmission to the mPFC and Amyg is involved in inhibitory control over responses to discriminated stimuli associated with the go/no-go paradigm common to both tests. In contrast, 5-HT neurotransmission to the OFC is especially involved in additional processes associated with reversal learning.
Masaki
Daiki
D
Department of Psychiatry, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Yokoyama
Chihiro
C
Kinoshita
Seijiro
S
Tsuchida
Hideto
H
Nakatomi
Yasuhito
Y
Yoshimoto
Kanji
K
Fukui
Kenji
K
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000679:Amygdala / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology; D004193:Discrimination Learning / Q000187:drug effects / Q000502:physiology; D004298:Dopamine / Q000378:metabolism; D005247:Feeding Behavior / Q000187:drug effects; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008032:Limbic System / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism; D017397:Prefrontal Cortex / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012193:Reversal Learning / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013315:Stress, Psychological / Q000523:psychology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D010133:p-Chloroamphetamine / Q000494:pharmacology*
D012702:Serotonin Antagonists; D015102:3,4-Dihydroxyphenylacetic Acid; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D010133:p-Chloroamphetamine; D004298:Dopamine