Effects of excitotoxic median raphe lesion on working memory deficits produced by the dorsal hippocampal muscarinic receptor blockade in the inhibitory avoidance in rats.
The experiments investigated the interactions between median raphe nucleus (MRN) serotonergic and septo-hippocampal muscarinic cholinergic systems in the modulation of forming and storing performances of working memory. Rats with ibotenic acid-induced MRN-lesion bilaterally received scopolamine (2-4 microg/each side) infusion into the dentate gyrus of the dorsal hippocampus and were tested in a single trial step-through inhibitory avoidance. Initial preference to the dark compartment (escape latency) was taken as the measure of non-mnemonic behaviours and response latency to enter the dark compartment immediately after the foot-shock was used to measure working memory. The high-dose scopolamine infusion 10 min before the training decreased escape latencies in the sham-lesioned rats, whereas had no effect in the MRN-lesioned rats. Although MRN lesion per se did not alter response latency, it alleviated pre-training scopolamine-induced decrease, but aggravated post-training scopolamine-induced reduction in this parameter. These results suggest that the antagonistic interactive processes between MRN-serotonergic and hippocampal cholinergic systems modulate non-mnemonic component of working memory formation, whereas the storing performance of working memory is modulated by the synergistic interactions between these systems in the hippocampus, mainly in the dentate gyrus.
Babar
Emine
E
Department of Physiology, Medical Faculty, University of Cukurova, 01330-Balcali/Adana, Turkey. ebabar@mail.cu.edu.tr
Melik
Enver
E
Ozgünen
Tuncay
T
Polat
Sait
S
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D002799:Cholinergic Fibers / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D020712:Fornix, Brain / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D007051:Ibotenic Acid / Q000494:pharmacology; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects* / Q000502:physiology; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009433:Neural Inhibition / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009498:Neurotoxins / Q000494:pharmacology; D011149:Pons / Q000187:drug effects / Q000293:injuries / Q000503:physiopathology*; D011903:Raphe Nuclei / Q000187:drug effects / Q000293:injuries / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000378:metabolism; D012601:Scopolamine / Q000494:pharmacology; D012686:Septal Nuclei / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D012701:Serotonin / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D018727:Muscarinic Antagonists; D009498:Neurotoxins; D011976:Receptors, Muscarinic; D007051:Ibotenic Acid; D012701:Serotonin; D012601:Scopolamine