Purinergic Signalling (2010) 6:429–445 DOI 10.1007/s11302-010-9207-6 ORIGINAL ARTICLE Purinergic receptor-mediated Ca2+ signaling in the olfactory bulb and the neurogenic area of the lateral ventricles Thomas Hassenklöver & Philipp Schulz & Anna Peters & Peter Schwartz & Detlev Schild & Ivan Manzini Received: 26 August 2010 / Accepted: 18 November 2010 / Published online: 1 December 2010 # The Author(s) 2010. This article is published with open access at Springerlink.com Abstract Like in other vertebrates, the anterior part of the telencephalon of amphibians mainly consists of the olfac- tory bulb (OB), but different from higher vertebrates, the lateral telencephalic ventricles of larval Xenopus laevis expand deep into the anterior telencephalon. The neuro- genic periventricular zone (PVZ) of the lateral ventricles generates new OB neurons throughout the animal’s life- time. We investigated the ultrastructural organization of the PVZ and found that within a time period of 24 h, 42.54 ± 6.65% of all PVZ cells were actively proliferating. Functional purinergic receptors are widespread in the central nervous system and their activation has been associated with many critical physiological processes, including the regulation of cell proliferation. In the present T. Hassenklöver : P. Schulz : A. Peters : D. Schild : I. Manzini (*) Department of Neurophysiology and Cellular Biophysics, University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany e-mail: imanzin@gwdg.de T. Hassenklöver : D. Schild : I. Manzini DFG Research Center for Molecular Physiology of the Brain (CMPB), University of Göttingen, Humboldtallee 23, 37073 Göttingen, Germany P. Schwartz Department of Anatomy and Embryology, Center of Anatomy, University of Göttingen, Kreuzbergring 36, 37075 Göttingen, Germany D. Schild DFG Cluster of Excellence 171, Humboldtallee 23, 37073 Göttingen, Germany study we identified and characterized the purinergic system of the OB and the PVZ. ATP and 2MeSATP induced strong [Ca2+]i increases in cells of both regions, which could be attenuated by purinergic antagonists. However, a more thorough pharmacological investigation revealed clear differences between the two brain regions. Cells of the OB almost exclusively express ionotropic P2X purinergic receptor subtypes, whereas PVZ cells express both iono- tropic P2X and metabotropic P1 and P2Y receptor subtypes. The P2X receptors expressed in the OB are evidently not involved in the immediate processing of olfactory information. Keywords P1 receptors . P2 receptors . Olfaction . Neuronal stem cells . Subventricular zone Introduction The anterior part of the telencephalon of larval Xenopus laevis is primarily involved in the processing of olfactory information. It mainly consists of the olfactory bulb (OB), the first relay center of the olfactory system. This structure processes chemosensory stimuli detected in the peripheral olfactory organs and transfers this information to higher brain centers [1]. The basic organization of the OB is highly conserved across phyla [2]. From the surface to the center, the OB can be subdivided in six discernible layers: the nerve layer, the glomerular layer, the external plexiform layer, the mitral cell layer, the internal plexiform layer and the granule cell layer. The most caudal layer, the granule cell layer, contacts the lateral telencephalic ventricles, which in larval X. laevis expand deep into the anterior telencephalon [3]. The area surrounding the lateral ven- tricles, the so-called periventricular zone (PVZ), has been