Sudomotor function and sweat gland innervation in galanin knockout mice Jorge J. Vilches a , David Wynick b , Barbara Kofler c , Roland Lang d , Xavier Navarro a,⇑ a Department of Cell Biology, Physiology and Immunology, Institute of Neurosciences and CIBERNED, Universitat Autònoma de Barcelona, Bellaterra, Spain b Schools of Physiology and Pharmacology and Clinical Sciences, Medical Sciences Building, University of Bristol, Bristol, UK c Research Program for Receptor Biochemistry and Tumor Metabolism, Laura Bassi Centre of Expertise THERAPEP, Department of Pediatrics, Paracelsus Medical University, Salzburg, Austria d Department of Dermatology, Paracelsus Medical University, Salzburg, Austria article info Article history: Received 20 January 2012 Accepted 17 May 2012 Available online 12 June 2012 Keywords: Galanin Sweat glands Sympathetic Sudomotor Heat stress abstract The presence of galanin and galanin binding sites in sweat gland has been demonstrated previously. In order to investigate whether galanin can influence sweat gland function, we compared sweating induced in footpads of wild type and galanin knockout mice by cholinergic and thermal stimulation using the silicone impression technique. Pilocarpine injections resulted in a similar number of reactive sweat glands and non-significant difference in the amount of sweat secretion in wild type and galanin knockout mice. However, thermal stimulation led to a significant increase in the number of secreting sweat glands in galanin knockout mice. To further evaluate possible differences in the innervation of sweat glands that could explain differences in their secretory activity, immunohistochemical labeling of cutaneous and sudomotor innervations against protein gene product 9.5, vasoactive intestinal polypeptide and choline acetyltransferase in plantar pads was performed. Immunohistochemical analysis revealed no significant differences in the distribution and intensity of the innervations between wild type mice and galanin knockout mice. Although our results indicate normal cholinergic responses and innervation of the sweat glands in galanin knockout mice, they also demonstrate that galanin plays a role in regulating the sudo- motor activity in response to thermal stimulation. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Sweat glands (SGs) are organs of neurobiological interest, whose main function is secreting sweat for thermoregulatory and emo- tional responses. SG secretion is under the direct control of postgan- glionic sympathetic sudomotor neurons. The cutaneous location of SGs allows to evaluate the sympathetic sudomotor function by means of noninvasive methods, such as silastic imprints and sweat output measurements, applicable in experimental models (Vilches et al., 2002; Bruna et al., 2010) as well as in clinical studies (Kennedy and Navarro, 1989; Low et al., 2006) for the assessment of neuro- pathic diseases and thermoregulatory disorders. Although the primary innervation of eccrine SGs is predomi- nantly adrenergic, during postnatal development it undergoes a transition in neurotransmitter phenotype to become mainly cholin- ergic (Stevens and Landis, 1987; Donadio et al., 2006). It has been well accepted that the acquisition of cholinergic properties is tar- get-dependent, developing after synaptic contacts are made with the gland cells (Stevens and Landis, 1990; Stanke et al., 2006). Nevertheless, Schütz et al. (2008) found that the pioneering neurons for SG innervation express a cholinergic/noradrenergic co-pheno- type before SG formation. Acetylcholine coexists with several neuropeptides, including vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and substance P in postgan- glionic sudomotor neurons and nerve terminals around SGs (Lindh et al., 1988; Anderson et al., 2006). Functionally, VIP has vasodilator properties and modulates the cholinergic response of SGs (Yamash- ita et al., 1987). Kummer et al. (1990) concluded that the major role of VIP is to regulate chloride reabsorption at the gland ductal seg- ment. It has been shown that CGRP enhances (Schlereth et al., 2006) and substance P inhibits cholinergic-induced sweating (Kumazawa et al., 1994), whereas Zancanaro et al. (1999) suggested that both neuropeptides are involved in an intrinsic regulatory activity of the SGs. The 29-30 aminoacid neuropeptide galanin (Tatemoto et al., 1983) is widely distributed in the central and peripheral nervous systems (Rökaeus et al., 1984; Ch’ng et al., 1985; Cheung et al., 1985; Skofitsch and Jacobowitz, 1985; Melander et al., 1986; Lang et al., 2007), and also present both in nerve terminals around SGs and in ductal cells (Tainio et al., 1987; Kofler et al., 2004; Holmberg et al., 2005; Bauer et al., 2008), but its role is unclear. The presence of galanin binding sites in SGs suggests that galanin might play a role in sudomotor function (Kofler et al., 2004). On the contrary, Holmberg et al. (2005) suggested that galanin receptors might not be present in SGs, since they reported no differences in 0143-4179/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.npep.2012.05.002 ⇑ Corresponding author. Address: Dept. Biologia Cellular, Fisiologia i Immunolo- gia, Unitat de Fisiologia, Facultat de Medicina, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain. Tel.: +34 935811966; fax: +34 935812986. E-mail address: xavier.navarro@uab.cat (X. Navarro). Neuropeptides 46 (2012) 151–155 Contents lists available at SciVerse ScienceDirect Neuropeptides journal homepage: www.elsevier.com/locate/npep