Available online at www.sciencedirect.com Behavioural Brain Research 189 (2008) 257–262 Research report The locus coeruleus involves in consolidation and memory retrieval, but not in acquisition of inhibitory avoidance learning task Behrooz Khakpour-Taleghani a , Reza Lashgari b,c,d,∗ , Tooka Aavani b , Abbas Haghparast b , Nima Naderi b , Fereshteh Motamedi b a Cellular & Molecular Research Center and Department of Physiology, School of Medicine, Guilan University of Medical Sciences, Rasht, Iran b Neuroscience Research Center and Department of Physiology, Shaheed Beheshti Medical University, Tehran, Iran c Imam Bagher(as) Institute of Science and Technology, Tehran, Iran d School of Cognitive Science, Institute for Studies in Theoretical Physics and Mathematics, Tehran, Iran Received 18 November 2007; received in revised form 1 January 2008; accepted 3 January 2008 Available online 18 January 2008 Abstract The locus coeruleus (LC) located at the level of the pons, is involved in cognitive functions such as learning and memory. The bilateral lidocaine- induced reversible inactivation of this nucleus has been considered in order to study its role in the phases of memory processing (acquisition, consolidation and retention) without any interference with the function of the same structure either during earlier and/or later phases of the same process. In this study, inhibitory avoidance (IA) learning task used to find the LC function in acquisition, consolidation and retrieval. Saline or lidocaine 4% (0.5 l/side) microinjected into the LC, for assessing the acquisition (5 min before training), consolidation (5, 90 and 360 min after training) and memory retrieval, 5 min before testing. The retention test was done 24 h after learning. Our results indicated that: (1) The bilateral functional inactivation of LC before training did not affect acquisition, but affected subsequent memory retention 24h later in IA task. (2) The lidocaine-induced inactivation of LC only 5 min after training impaired consolidation but did not affect it after 90 or 360 min. (3) Inactivation of the LC, 5min before pre-retrieval test, impaired memory retrieval in IA task. In conclusion, it seems that the nucleus locus coeruleus does not affect acquisition while it involves in the memory consolidation and retrieval of inhibitory avoidance learning task. Published by Elsevier B.V. Keywords: Locus coeruleus; Learning and memory; Reversible inactivation; Inhibitory avoidance task; Lidocaine; Rat 1. Introduction The locus coeruleus (LC) is a distinct cluster of neurons located near the wall of fourth ventricle at the level of the pons. It is the largest group of norepinephrine (NE)-containing neurons in the brain [26]. The locus coeruleus–norepinephrine (LC–NE) neurons have a diverse set of efferent projections throughout the brain regions (with the exception of the basal ganglia) and provides noradrenergic fiber distribution within and across the cerebral [33] and subcortical structures such as brainstem and hippocampus [29,33,36,59]. On the other hand, the LC receives ∗ Corresponding author at: Columbia University, 1051 Riverside Drive Unit 87, Kolb Research Annex (Room 569), New York, N.Y. 10032, United States. Tel.: +1 212 543 6931; fax: +1 212 543 5816. E-mail address: rlashgari@mahoney.cpmc.columbia.edu (R. Lashgari). inputs from CNS structures, substantially more restricted set of afferents arising from the prepositus hypoglossus and paragigan- tocellularis nuclei [5,8,10]. These unique anatomical properties indicate a possible role for this system in behavioral and cogni- tive functions [48]. Previous studies based on lesion and pharmacological manipulations have indicated that the LC–NE system has been implicated in several behavioral functions, including sleep/waking cycles [34], learning, memory and cognitive per- formances [16,24,30,45]. Crow [16] have previously proposed hypothesis that the LC plays an important role in establishing the synaptic changes underlying learning and memory. It has been indicated that electrical and chemical stimulation of the noradrenergic neurons in LC increase the NE release in the forebrain and as a result enhances memory retrieval [22,49,55]. While, electrical or chemical impairments and NE inhibition 0166-4328/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.bbr.2008.01.004