α GABA(A) subunit-orexin receptor interactions activate learning/motivational pathways in the goldfish.
Orexins (ORXs) cross-talking with γ-aminobutyric acid(A) receptor (GABA(A)R) is beginning to constitute a key neuronal signaling feature responsible for the successful promotion of sleep-wake cycle, feeding and motor behaviors plus reward/motivational activities. In this work, ORX-A and the two α GABA(A)R agonists (zolpidem, ZOL; diazepam, DZP) accounted for very great (p<0.001) increases of feeding while only DZP elicited great (p<0.01) levels of food intake in the goldfish (Carassius auratus). It was, however, T-maze and conditioned place preference (CPP) methods that allowed us to specifically establish learning/reward-related events operating in an ORX-A+GABA(A)R-dependent fashion in our experimental model. T-maze data showed that conditioned ORX-A treated-fish were capable of reaching the red/blue chamber and ingesting their food reward in a very greatly reduced latency time with respect to untreated conditioned fish while DZP and ZOL greatly and moderately (p<0.05) reduced their latency time, respectively. Regarding CPP study, conditioned ORX-A- and DZP-treated animals showed comparably greater preferences for the conditioned compartment that became even greater in ORX-A+DZP-treated fish. Surprisingly, ORX receptor expression of the telencephalon was preferentially activated by ORX-A treatments while diencephalic/mesencephalic structures and namely the tuberculum posterioris (TPp) were more sensitive to DZP especially following treatment with ORX-A+DZP. Overall, behavioral performances along with ORX receptor transcriptional properties tend to point to α GABA(A)R agonists as enhancers of palatability while the ORXergic system constitutes a crucial link between satiety-related and cognitive centers through the activation of TPp thus proposing this ascending dopaminergic system as a key target of learning/reward processes in fish.
Comparative Neuroanatomy Laboratory, Ecology Department, University of Calabria, 87036 Arcavacata di Rende (CS), Italy. rm.facciolo@unical.it
Rosa Maria
RM
Facciolo
Michele
M
Crudo
Merylin
M
Zizza
Giuseppina
G
Giusi
Marcello
M
Canonaco
D000704:Analysis of Variance; D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects; D003975:Diazepam / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D005247:Feeding Behavior / Q000187:drug effects; D018682:GABA Agents / Q000494:pharmacology; D018757:GABA Modulators / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006040:Goals; D006054:Goldfish; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism / Q000494:pharmacology*; D007858:Learning / Q000187:drug effects* / Q000502:physiology*; D009042:Motivation / Q000187:drug effects* / Q000502:physiology*; D009479:Neuropeptides / Q000378:metabolism / Q000494:pharmacology*; D000068797:Orexins; D009949:Orientation / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000235:genetics / Q000378:metabolism*; D012201:Reward; D000077334:Zolpidem
D018682:GABA Agents; D018757:GABA Modulators; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D011725:Pyridines; D011963:Receptors, GABA-A; D000077334:Zolpidem; D003975:Diazepam