ORIGINAL ARTICLE Purinergic receptor-induced Ca 2+ signaling in the neuroepithelium of the vomeronasal organ of larval Xenopus laevis Katarina Dittrich & Alfredo Sansone & Thomas Hassenklöver & Ivan Manzini Received: 19 September 2013 /Accepted: 4 November 2013 # The Author(s) 2013. This article is published with open access at Springerlink.com Abstract Purinergic signaling has considerable impact on the functioning of the nervous system, including the special senses. Purinergic receptors are expressed in various cell types in the retina, cochlea, taste buds, and the olfactory epithelium. The activation of these receptors by nucleotides, particularly adenosine-5′-triphosphate (ATP) and its breakdown products, has been shown to tune sensory information coding to control the homeostasis and to regulate the cell turnover in these organs. While the purinergic system of the retina, cochlea, and taste buds has been investigated in numerous studies, the available information about purinergic signaling in the olfac- tory system is rather limited. Using functional calcium imag- ing, we identified and characterized the purinergic receptors expressed in the vomeronasal organ of larval Xenopus laevis . ATP-evoked activity in supporting and basal cells was not dependent on extracellular Ca 2+ . Depletion of intracellular Ca 2+ stores disrupted the responses in both cell types. In addition to ATP, supporting cells responded also to uridine- 5 ′ -triphosphate (UTP) and adenosine-5 ′ -O-(3- thiotriphosphate) (ATPγS). The response profile of basal cells was considerably broader. In addition to ATP, they were activated by ADP, 2-MeSATP, 2-MeSADP, ATPγS, UTP, and UDP. Together, our findings suggest that supporting cells express P2Y 2 /P2Y 4 -like purinergic receptors and that basal cells express multiple P2Y receptors. In contrast, vomeronasal receptor neurons were not sensitive to nucleotides, suggesting that they do not express purinergic receptors. Our data provide the basis for further investigations of the physiological role of purinergic signaling in the vomeronasal organ and the olfac- tory system in general. Keywords P2Y receptors . Olfactory system . Calcium imaging . Pharmacological characterization Introduction The vomeronasal system is present as a discrete sensory system only in tetrapods. It first appeared in amphibians ([1, 2] but see [3]), and it is present from larval to adult stages in most amphibian species [4]. The vomeronasal organ (VNO) is the peripheral sensory organ of the vertebrate accessory olfactory system [5]. The VNO has been shown to mediate the detection of pheromones [4, 5], but in Xenopus its function still remains to be elucidated. It consists of a neuroepithelium containing the same three main cell types as the vertebrate main olfactory epithelium (MOE): (1) receptor neurons which transmit the sensory information from the periphery to the accessory olfac- tory bulb in the brain, (2) supporting cells (SCs) which share common properties with glial and epithelial cells, and (3) basal cells (BCs), stem cells which maintain the regenerative capac- ity of the organ. Specifically, the VNO of larval Xenopus laevis is made of microvillous vomeronasal receptor neurons (VRNs), ciliated SCs, and a population of BCs. The Xenopus MOE, in contrast, consists of microvillous and ciliated olfactory receptor neurons (ORNs), ciliated and secretory SCs, and a population of BCs; for a more detailed overview of the cellular organiza- tion of the Xenopus olfactory organ, see [1, 6]. It has been shown that SCs and BCs in the Xenopus and mouse MOE express purinergic receptors [7–10]. In both species, application of nucleotides to the MOE induces strong wave-like intracellular Ca 2+ ([Ca 2+ ] i ) increases in SCs that propagate from the apical to the basal part of the MOE [8, 11], suggesting that they are a common feature of the K. Dittrich : A. Sansone : T. Hassenklöver : I. Manzini (*) Institute of Neurophysiology and Cellular Biophysics, University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany e-mail: imanzin@gwdg.de T. Hassenklöver : I. Manzini Center for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37073 Göttingen, Germany Purinergic Signalling DOI 10.1007/s11302-013-9402-3