Paper Information

Journal:   BASIC AND CLINICAL NEUROSCIENCE   SUMMER 2011 , Volume 2 , Number 4; Page(s) 27 To 35.
 
Paper:  THE EFFECTS OF LIDOCAINE REVERSIBLE INACTIVATION OF THE DORSAL RAPHE NUCLEUS ON PASSIVE AVOIDANCE LEARNING IN RATS
 
Author(s):  SARIHI ABDOLRAHMAN*, YAZDI MEISAM, HESHMATIAN BEHNAM, SALEHI IRAJ, BEHZADI GILA, NAGHDI NASSER, SHAHIDI SIAMAK, KOMAKI ALIREZA, HAGHPARAST ABBAS, EMAM AMIR HOSSEIN
 
* NEUROPHYSIOLOGY RESEARCH CENTER, HAMADAN UNIVERSITY OF MEDICAL SCIENCES, HAMADAN, IRAN
 
Abstract: 

Introduction: The role of serotonergic fibers in avoidance learning is controversial. Involvement of the dorsal raphe nucleus (DRN), the main source of hippocampal projecting serotonergic fibers in acquisition, consolidation and retrieval of passive avoidance (PA) learning, was investigated by functional suppression of this area.
Materials and Methods: DRN functional inactivation was done by lidocaine (0.5
ml, 2%) injection into the DRN, 5 min before training (n=10); and 5 (n=9), 90 (n=10) and 360 min (n=9) after acquisition trial. In the last experiment, lidocaine was injected into the DRN 5 min before the retrieval test, which was 48 h after the training (n=10).
Results: Our results showed that PA learning was not impaired by DRN inactivation 5 min before training nor 5 and 360 min after training. Lidocaine injected 90 min after the acquisition trial significantly reduced avoidance of the dark compartment (P<0.001). Intra-DRN injection of lidocaine before retrieval significantly increased PA retention (P<0.001). Therefore, it seems that DRN has opposite effects on consolidation and retrieval of passive avoidance learning, but it has no effect on PA acquisition.
Discussion: It is suggested that functional ablation of DRN may disrupt integrity of subcortical circuits participating in PA consolidation, but DRN inactivation by increasing brain awareness may affect PA retrieval in rats.

 
Keyword(s): DORSAL RAPHE, PASSIVE AVOIDANCE, REVERSIBLE INACTIVATION, LEARNING AND MEMORY, LIDOCAINE, RAT
 
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