Zinc Modulation of a Transient Potassium Current and Histochemical Localization of the Metal in Neurons of the Suprachiasmatic Nucleus

• Published in: Proceedings of the National Academy of Sciences - PNAS 1993-12, Vol.90 (24), p.11806-11810
• Main Authors: Huang, Rong-Chi, Peng, You-Wei, Yau, King-Wai
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Brain; Cellular biology; Central nervous system; Electric current; Electric potential; Electrophysiology; Evoked Potentials - drug effects; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Ion Channel Gating - drug effects; Membrane potential; Membrane Potentials - drug effects; Neurology; Neurons; Neurons - cytology; Neurons - physiology; Neuroscience; Potassium; Potassium Channels - drug effects; Potassium Channels - physiology; Rats; Rats, Sprague-Dawley; Sodium; Suprachiasmatic nucleus; Suprachiasmatic Nucleus - cytology; Suprachiasmatic Nucleus - physiology; Synapses; Vertebrates: nervous system and sense organs; Zinc; Zinc - analysis; Zinc - metabolism; Zinc - pharmacology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.90.24.11806

The effect of Zn2+on a voltage-dependent, transient potassium current (IA) in acutely dissociated neurons from the suprachiasmatic nucleus was studied with the whole-cell patch-clamp technique. At micromolar concentrations, Zn2+markedly potentiated IAactivated from a holding potential of -60 mV, which is the resting potential of these neurons. This potentiation occurred at a Zn2+concentration as low as 2 μ M and increased with higher Zn2+concentrations. The Zn2+action appears to arise from a shift in the steady-state inactivation of IAto more positive voltages. At 30 μ M, Zn2+shifted the half-inactivation voltage by +20 mV (from -80 mV to -60 mV), and 200 μ M Zn2+shifted this voltage by +45 mV (from -80 mV to -35 mV). Histochemically, we have also observed Zn2+staining throughout the suprachiasmatic nucleus; the staining is particularly intense in the ventrolateral region of the nucleus, which receives the major fiber inputs. Our findings suggest that Zn2+, presumably synaptically released, may modulate the electrical activity of suprachiasmatic nucleus neurons through IA. Because vesicular Zn2+is fairly wide-spread in the central nervous system, it is conceivable that this kind of Zn2+modulation on IA, and possibly on other voltage-activated currents, exists elsewhere in the brain.