Research Report The role of GABAergic transmission in the dentate gyrus on acquisition, consolidation and retrieval of an inhibitory avoidance learning and memory task in the rat Siamak Shahidi a, ⁎ , Alireza Komaki a , Minoo Mahmoodi b , Reza Lashgari c,d,e a Department of Physiology, School of Medicine, Hamadan University of Medical Sciences, Hamedan, Iran b Department of Biology, Islamic Azad University, Hamedan Branch, Hamedan, Iran c Neuroscience Research Center, Shaheed Beheshti University of Medical Sciences, Tehran, Iran d Imam Bagher (as) Institute of Science and Technology, Tehran, Iran e Center for Neurobiology and Behavior and Department of Psychiatry, Columbia University, New York, NY 10032, USA ARTICLE INFO ABSTRACT Article history: Accepted 3 February 2008 Available online 14 February 2008 The hippocampal GABAergic interneurons are responsible for controlling the input of large principal cell populations, and they thereby determine the oscillatory discharge patterns and synaptic plasticity in the hippocampus. Such oscillations within neuronal systems serve various complex functions, such as perception, cognition, plasticity and memory. The aim of this study is to define the function of GABAergic synaptic transmission in the dentate gyrus (DG) of the hippocampus in the different stages of inhibitory avoidance (IA) learning and memory in the rat. Two cannulae were implanted above the hippocampal DG. Then the rats were trained on a step-through IA learning task. Each rat received intra-DG injection of picrotoxin (PTX) or saline before training, after training or before the retrieval test. The results show that post-training injection of PTX impaired the IA memory. On the other hand, pre-training and pre-retrieval injection of PTX had no significant effect on the IA activity. Therefore, it seems that GABAergic transmission in the DG is involved in the consolidation step (but not in the acquisition and retrieval steps) of the IA task by controlling the input to the principal cells. © 2008 Elsevier B.V. All rights reserved. Keywords: Picrotoxin Dentate gyrus Inhibitory avoidance learning Rat 1. Introduction Learning and memory are complex processes (Das, 2003; Mar- kowitsch, 1997; Fuster, 1998; Goldman-Rakic, 1996; Lu and Figurov, 1997) that have several stages, including acquisition, consolidation and retrieval (Okano et al., 2000; Abel and Mat- thew, 2001). A number of neurotransmitters are in some way involved in the formation and retrieval of memory traces (Das, 2003; Farr et al, 2000). The GABAergic system is critically involved in cognitive processes, especially learning and memory (Castel- lano et al, 1993; Chapouthier and Venault, 2002; Garden et al, 2002; Toso et al, 2007; Berlau and McGaugh, 2006; Zarrindast et al, 2006; Lee et al, 2006; Ramirez et al, 2005; Jiang et al, 2005; Collinson et al 2002; Zarrindast et al, 2004). Previous studies have BRAIN RESEARCH 1204 (2008) 87 – 93 ⁎ Corresponding author. Fax: +98 811 8276299. E-mail address: siamakshahidi@yahoo.com (S. Shahidi). 0006-8993/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.brainres.2008.02.008 available at www.sciencedirect.com www.elsevier.com/locate/brainres