Neuroscience Letters 424 (2007) 170–174 Immunohistochemical localization of TRPC6 in the rat substantia nigra Carmela Giamp` a a , Zena DeMarch a , Stefano Patassini a , Giorgio Bernardi a,b , Francesca R. Fusco a,* a Santa Lucia Foundation Hospital at the European Center for Brain Research, Laboratory of Neuroanatomy, Rome, Italy b University of Rome Tor Vergata, Department of Neuroscience, Rome, Italy Received 14 June 2007; received in revised form 12 July 2007; accepted 13 July 2007 Abstract Transient receptor potential channels (TRPC) are plasma membrane, nonselective cationic channels and have been proposed as candidates involved in the regulation of cellular Ca 2+ influx [D.E. Clapham, L.W. Runnels, C., Strubing, The TRP ion channel family, Nat. Rev. Neurosci. 2 (2001) 387–396; A. Martorana, C. Giampa, Z. DeMarch, M.T. Viscomi, S. Patassini, G. Sancesario, G. Bernardi, F.R. Fusco, Distribution of TRPC1 receptors in dendrites of rat substantia nigra: a confocal and electron microscopy study, Eur. J. Neurosci. 24 (2006) 732–738]. Studies on regional localization patterns of TRPCs are necessary to provide helpful guidelines for correlating current types with particular channels. In this study, we examined the distribution of one particular member of TRPC superfamily, namely, TRPC6, in the substantia nigra of normal rat brain. Single and double label immunohistochemistry were employed to perform both light and confocal microscopy observations. Our single label studies showed that, in the substantia nigra, TRPC6 labeled the perikarya with a diffuse and intense immunoreaction product distributed throughout cell cytoplasm whereas only a light immunostaining was observed in the cell nuclei. No labeling of axon or terminals was observed, although TRPC6 was evenly distributed in the neuropil. Our dual label studies showed a TRPC6 immunoreactivity pattern that was localized into the proximal dendrites and axon hillock of the large dopaminergic neurons identified by TH immunoreaction. Furthermore, our double label immunofluorescence study for TRPC6 and mGluR1 showed a complete co-localization of the two markers in the substantia nigra. Moreover, TRPC6 did not co-localize with synaptophysin. Thus, our study shows the postsynaptic localization of TRPC6 and its association with mGluR1 in the midbrain dopamine neurons. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Midbrain; Store-operated calcium entry; Immunohistochemistry; Confocal microscopy; Transient receptor potential channels Transient receptor potential (TRP) channels are plasma mem- brane, nonselective cationic channels and have been proposed as candidates involved in the regulation of cellular Ca 2+ influx [6,18]. The TRP superfamily consists of six subfamilies, includ- ing the “classical canonical TRPs” (TRPC subfamily) [13,19], the TRPV, the TRPN, the TRPM, TRPP and TRPML subfamilies [6,20]. The TRPC subfamily consists of 7 subgroups, which can be subdivided into four groups based on the primary amino-acid sequences. TRP channels can act as a plasma membrane cationic channel that is permeable to Na + and Ca 2+ [1]. These proteins contribute to Ca 2+ influx evoked by activation of the phospholipase C path- way and/or by Ca 2+ store depletion [17]. Cation conductance * Corresponding author at: Santa Lucia Foundation IRCCS Hospital at the European Centre for Brain Research, Via del Fosso Fiorano 64, 00179, Rome, Italy. Tel.: +39 06 50170 3072; fax: +39 06 50170 3325. E-mail address: f.fusco@hsantalucia.it (F.R. Fusco). is coupled to the activation of phospholipase C (PLC), with a mechanism that seems to be mediated by the TRP superfam- ily of proteins [19]. Neuronal and non-neuronal cells in the brain respond to various stimuli utilizing calcium entry, and TRPCs are distributed in both neurons and glia. Moreover, the co-expression of several TRPCs was demonstrated previously in central aminergic neurons [24]. The association between specialized functions in each brain region and the distribution of TRP isoforms merits examination. In particular, stimulation of substantia nigra neurons produces dopamine and this stimulation involves Ca 2+ entry [7]. More- over, substantia nigra differs from the whole brain in its TRP expression [26]. In previous studies, we described the localization of a mem- ber of TRP superfamily, namely, TRPC3, in oligodendrocytes of substantia nigra and other brain regions in normal rat brain [11]. Moreover, we have shown the distribution of TRPC5 in the nuclei of substantia nigra dopaminergic neurons [8]. Finally, 0304-3940/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2007.07.049