Available online at www.sciencedirect.com Neuroscience Letters 436 (2008) 19–22 Taurine improves learning and retention in aged mice Abdeslem El Idrissi a,b,∗ a Department of Biology, The Center for Developmental Neuroscience, College of Staten Island, 2800 Victory Blvd., 6S-316 Staten Island, NY 10314, United States b The Graduate Center, Program in Biology-Neurosciences, The City University of New York, 365 Fifth Avenue, New York, NY 10016, United States Received 2 June 2007; received in revised form 16 February 2008; accepted 21 February 2008 Abstract Aging of the brain is characterized by several neurochemical modifications involving structural proteins, neurotransmitters, neuropeptides and related receptors. Alterations of neurochemical indices of synaptic function have been considered as indicators of age-related impairment of central functions, such as locomotion, memory and sensory performances. Several studies demonstrated that GABA receptors, glutamic acid decarboxylase (GAD65&67), and different subpopulations of GABAergic neurons are markedly decreased in experimental animal brains during aging. Thus, the age-related decline in cognitive functions could be attributable, at least in part, to decrements in GABA inhibitory neurotransmission. In this study, using a passive avoidance test, we show that chronic supplementation of taurine to aged mice significantly ameliorates the age-dependent decline in memory acquisition and retention. We have previously shown that taurine supplementation caused changes in the GABAergic system. These changes include increased levels of the neurotransmitters GABA and glutamate, increased expression of glutamic acid decarboxylase and the neuropeptide somatostatin and increase in the number of somatostatin-positive neurons. These specific alterations of the inhibitory system caused by taurine treatment oppose those naturally occurring in aging, and suggest a protective role of taurine against the normal aging process. Increased understanding of age-related neurochemical changes in the GABAergic system will be important in elucidating the underpinnings of the functional changes of aging. Taurine might help forestall the age-related decline in cognitive functions through alterations of the GABAergic system. © 2008 Elsevier Ireland Ltd. All rights reserved. Keywords: Taurine; Aging; Passive avoidance; Learning; GABA; Somatostatin Aging of the brain is characterized by several neurochemical modifications involving structural proteins, neurotransmitters, neuropeptides and related receptors [22]. Alterations of neuro- chemical indices of synaptic function have been considered as indicators of age-related impairment of central functions, such as locomotion, memory and sensory performances. Age-related impairments of cognitive and motor functions have been linked to a number of deleterious functional and morphological changes involving different areas of the brain. Loss of neurotransmit- ters, their receptors and responsiveness to neurotransmitters are key manifestations of neurological aging and age-related disor- ders. Reductions of the levels of transmitter substances and of the activities of enzymes involved in their synthesis have been demonstrated in the aging brain [5,6]. Furthermore, neurotrans- mitter systems are not equally sensitive to aging and almost ∗ Correspondence address. Department of Biology, The Center for Devel- opmental neuroscience, College of Staten Island, 2800 Victory Blvd., 6S-316 Staten Island, NY 10314, United States. Tel.: +1 718 982 3863. E-mail address: elidrissi@mail.csi.cuny.edu. all neurotransmitter systems are affected in aging. Many studies have shown age-associated abnormalities in peptidergic, cholin- ergic, monoaminergic and amino acid neurotransmitter systems and suggest that changes in brain biochemistry contribute directly to deficits in learning and memory. In this study, we have focused on the inhibitory system because of the important role this neurotransmitter system plays in normal and abnormal brain function. GABA is the primary inhibitory neurotransmitter and is present in neurons in all brain regions. Furthermore, a num- ber of GABAergic parameters have been reported to undergo changes during senescence [1]. Age-related changes associ- ated with GABA neurotransmitter function involve almost all aspects of synaptic transmission. These include decreased num- ber of GABA immunoreactive neurons, decreased basal levels (concentrations) of GABA, decreased GABA release, decreased GAD activity, decreased GABA B receptor binding, decreased numbers of presynaptic terminals, and subtle GABA A recep- tor binding changes [7]. Collectively, these age-related changes suggest altered GABA neurotransmitter function in the brain during senescence. 0304-3940/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2008.02.070