title: Significance of Low Nanomolar Concentration of Zn2+in Artificial Cerebrospinal Fluid.
abstract: Much less attention has been paid to Zn2+in artificial cerebrospinal fluid (ACSF), i.e., extracellular medium, used for in vitro slice experiments than divalent cations such as Ca2+. Approximately 2 mM Ca2+is added to conventional ACSF from essentiality of Ca2+signaling in neurons and glial cells. However, no Zn2+is added to it, even though the importance of Zn2+signaling in them is recognizing. On the other hand, synaptic Zn2+homeostasis is changed during brain slice preparation. Therefore, it is possible that not only neuronal excitation but also synaptic plasticity such as long-term potentiation is modified in ACSF without Zn2+, in which original physiology might not appear. The basal (static) levels of intracellular (cytosolic) Zn2+and Ca2+are not significantly different between brain slices prepared with conventional ACSF without Zn2+and pretreated with ACSF containing 20 nM ZnCl2for 1 h. In the case of mossy fiber excitation, however, presynaptic activity assessed with FM 4-64 is significantly suppressed in the stratum lucidum of brain slices pretreated with ACSF containing Zn2+, indicating that hippocampal excitability is enhanced in brain slices prepared with ACSF without Zn2+. The evidence suggests that low nanomolar concentration of Zn2+is necessary for ACSF. Furthermore, exogenous Zn2+has opposite effect on LTP induction between in vitro and in vivo experiments. It is required to pay attention to extracellular Zn2+concentration to understand synaptic function precisely.
authors.affiliation: Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan. takedaa@u-shizuoka-ken.ac.jp.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takeda
authors.affiliation: Department of Neurophysiology, School of Pharmaceutical Sciences, University of Shizuoka, 52- 1 Yada, Suruga-ku, Shizuoka, 422-8526, Japan.
authors.forename: Haruna
authors.initials: H
authors.lastname: Tamano
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D006624:Hippocampus / Q000502:physiology; D006801:Humans; D017774:Long-Term Potentiation; D009474:Neurons / Q000502:physiology; D015032:Zinc / Q000032:analysis* / Q000134:cerebrospinal fluid*
chemical_list: D015032:Zinc
keywords: Artificial cerebrospinal fluid; Brain slice; Hippocampus; In vitro experiment; Zn2+