PT  - JOURNAL ARTICLE
AU  - P Seguela
AU  - J Wadiche
AU  - K Dineley-Miller
AU  - JA Dani
AU  - JW Patrick
TI  - Molecular cloning, functional properties, and distribution of rat brain alpha 7: a nicotinic cation channel highly permeable to calcium
AID  - 10.1523/JNEUROSCI.13-02-00596.1993
DP  - 1993 Feb 01
TA  - The Journal of Neuroscience
PG  - 596--604
VI  - 13
IP  - 2
4099  - http://www.jneurosci.org/content/13/2/596.short
4100  - http://www.jneurosci.org/content/13/2/596.full
SO  - J. Neurosci.1993 Feb 01; 13
AB  - A full-length clone coding for the rat alpha 7 nicotinic receptor subunit was isolated from an adult brain cDNA library and expressed in Xenopus oocytes. A significant proportion of the current through alpha 7-channels is carried by Ca2+. This Ca2+ influx then activates a Ca(2+)- dependent Cl- conductance, which is blocked by the chloride channel blockers niflumic and fluflenamic acid. Increasing the external NaCl concentration caused the reversal potentials for the alpha 7-channels and the Ca(2+)-dependent Cl- channels to be shifted in opposite directions. Under these conditions, agonist application activates a biphasic current with an initial inward current through alpha 7- channels followed by a niflumic acid- and fluflenamic acid-blockable outward current through Ca(2+)-dependent Cl- channels. A relative measure of the Ca2+ permeability was made by measuring the shift in the reversal potential caused by adding 10 mM Ca2+ to the external solution. Measurements made in the absence of Cl-, to avoid artifactual current through Ca(2+)-activated Cl- channels, indicate that alpha 7- homooligomeric channels have a greater relative Ca2+ permeability than the other nicotinic ACh receptors. Furthermore, alpha 7-channels have an even greater relative Ca2+ permeability than the NMDA subtype of glutamate receptors. High levels of alpha 7-transcripts were localized by in situ hybridization in the olfactory areas, the hippocampus, the hypothalamus, the amygdala, and the cerebral cortex. These results imply that alpha 7-containing receptors may play a role in activating calcium-dependent mechanisms in specific neuronal populations of the adult rat limbic system.