Please cite this article in press as: Canas, P.M., et al., Modification upon aging of the density of presynaptic modulation systems in the hippocampus, Neurobiol Aging (2008), doi:10.1016/j.neurobiolaging.2008.01.003 ARTICLE IN PRESS NBA-7009; No. of Pages 8 Neurobiology of Aging xxx (2008) xxx–xxx Modification upon aging of the density of presynaptic modulation systems in the hippocampus Paula M. Canas 1 , Jo˜ ao M.N. Duarte 1 , Ricardo J. Rodrigues 1 , Attila K ¨ ofalvi 1 , Rodrigo A. Cunha ∗ Centre for Neuroscience of Coimbra, Institute of Biochemistry, Faculty of Medicine, University of Coimbra, Rua Larga, 3004-504 Coimbra, Portugal Received 30 October 2007; received in revised form 29 December 2007; accepted 8 January 2008 Abstract Different presynaptic neuromodulation systems have been explored as possible targets to manage neurodegenerative diseases. However, most studies used young adult animals whereas neurodegenerative diseases are prevalent in the elderly. Thus, we now explored by Western blot analysis how the density of different presynaptic markers and receptors changes with aging in rat hippocampal synaptosomes (purified nerve terminals). Compared to synaptosomal membranes from 2-month-old rats, the density of presynaptic proteins (synaptophysin or SNAP-25) decreased at 18–24 months. In parallel, markers of glutamatergic terminals (vGluT1 or vGluT2) and cholinergic terminal markers (vAChT) constantly decreased with aging from 12 to 18 months onwards, whereas the densities of GABAergic (vGAT) only decreased after 24 months. Inhibitory A 1 and CB 1 receptor density tended to decrease with aging, whereas facilitatory mGluR5 and P2Y1 receptor density was roughly constant and facilitatory A 2A receptor density increased at 18–24 months. Thus aging causes an imbalance of excitatory versus inhibitory nerve terminal markers and causes a predominant decrease of inhibitory rather than facilitatory presynaptic modulation systems. © 2008 Elsevier Inc. All rights reserved. Keywords: Aging; Nerve terminals; Density; Adenosine; A 1 ;A 2A ; CB 1 ; P2Y1; Metabotropic; Glutamate; MGluR5; GABA; Acetylcholine; Synaptophysin 1. Introduction There is increasing evidence indicating that dysfunction and loss of nerve terminals might represent one of the earli- est modifications in the course of neurodegenerative diseases (Wishart et al., 2006). For instance, in Alzheimer’s disease, the loss of synaptic markers, in contrast to neuronal loss, is the parameter that correlates better with memory dys- function (Selkoe, 2002). Likewise, in Parkinson’s disease, modification of firing patterns of cortico-striatal pathways (B´ ezard et al., 2003) and loss of dopaminergic terminals (Herkenham et al., 1991) occur early in the asymptomatic ∗ Corresponding author. Tel.: +351 239820190; fax: +351 239822776. E-mail address: racunha@ci.uc.pt (R.A. Cunha). URL: http://www/cnc.cj.uc.pt/lab lef/ (R.A. Cunha). 1 These authors contributed experimentally for the present work. The authors are grateful to Dr. Ken Mackie for generously supply of the CB 1 receptor antibody. phase of the disease. In fact, this synaptic dysfunction and damage has been recognised as an early event in the course of different other neurodegenerative diseases such as Huntington’s (Li et al., 2001), prion’s diseases (Ferrer, 2002), HIV infection (Garden et al., 2002), schizophre- nia (Glantz et al., 2006), temporal lobe epilepsy (Ratt´ e and Lacaille, 2006) or motor neuropathies (Raff et al., 2002). This central and initial role of synaptic dysfunction in neu- rodegenerative diseases has been the main driving force to conceive presynaptic neuromodulation systems as candidate targets to restraint the early modifications in these diseases. Thus, drugs activating presynaptic modulators such as adeno- sine A 1 receptors (Fredholm et al., 2005) or cannabinoid CB 1 receptors (van der Stelt and Di Marzo, 2005) might afford protection against different neurodegenerative diseases. Also, antagonists of adenosine A 2A receptors (Fredholm et al., 2005), metabotropic group 5 receptors (Flor et al., 2002) or ATP P2Y1 receptors (Franke et al., 2006) also confer neu- 0197-4580/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.neurobiolaging.2008.01.003