title: Differential Na(+)-K(+)-ATPase activity in rat lemniscal and non-lemniscal auditory thalami.
abstract: 1. Using whole-cell recording and confocal immunofluorescent microscopy, we have investigated the differential electrogenic activity, subunit expression and subcellular distribution of the Na(+)-K(+)-ATPase in the lemniscal (ventral) and non-lemniscal (dorsal) pathways of the rat medial geniculate body (MGB) in vitro. 2. Bath application of Na(+)-K(+)-ATPase inhibitors strophanthidin or dihydro-ouabain produced a transient, dose-dependent inward current or membrane depolarization which were significantly larger in dorsal MGB neurones than in ventral cells (45.9 +/- 6.45 vs. 24.3 +/- 4.1 pA; P < 0.05). Electrophysiological and morphometric measurements showed that the dorsal MGB neurones had a significantly lower input conductance and a smaller somata than their ventral counterparts. The level of the resting membrane potential also differed by about 6 mV between the two cell populations, with the dorsal cells being more hyperpolarized (-74.2 +/- 0.6 vs. -67.7 +/- 1.3 mV; P < 0.001). 3. Incubation of enzymatically dissociated MGB neurones with fluorescent monoclonal antibodies against alpha 1-alpha 3 isoforms of Na(+)-K(+)-ATPase showed that both dorsal and ventral cells expressed primarily alpha 3 subunits. Confocal laser scanning revealed, however, that the mean pixel density of alpha 3 fluorescent antibodies in the plasma membrane domain, but not in the cytoplasmic compartment, was about 40% higher in dorsal neurones than in the ventral cells (29.7 +/- 4.7 vs. 16.9 +/- 2.3 grey shadow per pixel; P < 0.05). 4. The above results suggest that the electrogenic activity of the Na(+)-K(+)-ATPase is differentially regulated between lemniscal and non-lemniscal auditory thalami through a mechanism that probably involves differential pump densities in the cell membrane.
authors.affiliation: Loeb Medical Research Institute, Ottawa Civic Hospital, University of Ottawa, Ontario, Canada.
authors.forename: V V
authors.initials: VV
authors.lastname: Senatorov
authors.forename: B
authors.initials: B
authors.lastname: Hu
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D001306:Auditory Pathways; D005829:Geniculate Bodies / Q000201:enzymology / Q000502:physiology*; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D046911:Macromolecular Substances; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008959:Models, Neurological; D009474:Neurons / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D009924:Organ Culture Techniques; D010042:Ouabain / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D013327:Strophanthidin / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D007527:Isoenzymes; D046911:Macromolecular Substances; C000977:dihydroouabain; D010042:Ouabain; D013327:Strophanthidin; D000254:Sodium-Potassium-Exchanging ATPase