Talanta 85 (2011) 1933–1940 Contents lists available at ScienceDirect Talanta j ourna l ho me page: www.elsevier.com/locate/talanta Dual asymmetric-flow microdialysis for in vivo monitoring of brain neurochemicals Gianfranco Bazzu ∗ , Alice Biosa, Donatella Farina, Ylenia Spissu, Sonia Dedola, Giammario Calia, Giulia Puggioni, Gaia Rocchitta, Rossana Migheli, Maria Speranza Desole, Pier Andrea Serra Department of Neuroscience, Medical School, University of Sassari, Viale San Pietro 43/b, 07100 Sassari, Italy a r t i c l e i n f o Article history: Received 18 January 2011 Received in revised form 21 June 2011 Accepted 7 July 2011 Available online 18 July 2011 Keywords: In vivo microdialysis Liquid chromatography Dopamine Glutamate Brain bioenergetics Glucose Lactate Pyruvate Ascorbic acid Rat striatum a b s t r a c t Microdialysis is an extensively used technique for both in vivo and in vitro experiments, applicable to animal and human studies. In neurosciences, the in vivo microdialysis is usually performed to follow changes in the extracellular levels of substances and to monitor neurotransmitters release in the brain of freely moving animals. Catecholamines, such as dopamine and their related compounds, are involved in the neurochemistry and in the physiology of mental diseases and neurological disorders. It is generally supposed that the brain’s energy requirement is supplied by glucose oxidation. More recently, lactate was proposed to be the metabolic substrate used by neurons during synaptic activity. In our study, an innovative microdialysis approach for simultaneous monitoring of catecholamines, indolamines, gluta- mate and energy substrates in the striatum of freely moving rats, using an asymmetric perfusion flow rate on microdialysis probe, is described. As a result of this asymmetric perfusion, two samples are avail- able from the same brain region, having the same analytes composition but different concentrations. The asymmetric flow perfusion could be a useful tool in neurosciences studies related to brain’s energy requirement, such as toxin-induced models of Parkinson’s disease. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Microdialysis is a technique for sampling the chemistry from most brain regions, tissues and organs with limited tissue traumas [1,2]. The idea of this technique, developed in 1972 [3] and popu- larized by Ungerstedt and Pycok [4], was to implant a thin dialysis tube into the tissue to mimic the function of a blood vessel artifi- cial capillary, whereby substances may be both topically recovered from and supplied to a tissue [5]. Although based on a very simple principle, microdialysis is one of the most widely used techniques for in vivo and in vitro sampling of the chemical substances in extra- cellular fluids of animal tissues or cultured cells. The microdialysis probe employs the dialysis principle according to whom a semi per- meable membrane, introduced into a tissue or placed into contact with a moist surface, separates two fluid compartments. The probe is perfused with a liquid and the low molecular weight compounds diffuse down their concentration gradients in both directions. The collected perfusion fluid can be analyzed with different analytical systems such as spectrophotometer [6], microsensors [7] or HPLC with electrochemical [8], UV and fluorescence [9] detectors. The ∗ Corresponding author. Tel.: +39 079228528; fax: +39 079228525. E-mail addresses: gbazzu@uniss.it, gbazzu@gmail.com (G. Bazzu). sensitivity of the used analytical technique is the limit of micro- dialysis [10]. A prerequisite of many neurological studies is an accurate and continuous monitoring of in vivo concentrations of substances in the brain extracellular space. The combination of microdialysis with highly sensitive analytical techniques allows the measure- ment of a lot of neuroactive compounds [11]. Catecholamines and their related compounds are involved in the neurochemistry and in the physiology of mental diseases and neurological disorders. A significant reduction of striatal content of dopamine (DA) [8], a catechol-like neurotransmitter implicated in cognitive func- tions [12] and in reward pathways [13], and of its catabolites dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) [14] and 3-methoxytyramine (3-MT) [15], is a hallmark in Parkinson’s disease [16,17]. Catecholamines biochemical dynamics have been studied extensively both in vivo and in vitro [18–23]. The mammalian brain is an expensive energy-consuming organ [24]. Most of brain’s energy consumption is due to neuronal activity (about 80%) and other processes such as neurotransmitter recycling and axonal and dendritic transport [25]. At the moment, there is a controversy concerning the energy substrate used by the activated neurons and metabolic changes during neuronal activation [26,27]. Under normal physiological conditions, glucose is the major source 0039-9140/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2011.07.018