Assay for the presence, in cultured cells, of functional ligand-gated channels, and substances which enhance intracellular lithium accumulation by cultured cells via such channels

A method for determining whether a compound is, directly or indirectly, an agonist or antagonist for ligand-gated channels expressed by cells, said method comprising:

• (a) contacting said cells with an effective amount of said compound in the presence of a lithium ion-containing flux buffer for a time sufficient to allow the intracellular accumulation of lithium, by both passive and non-passive means, but not so long as to allow the amount of passive lithium accumulation to substantially exceed the amount of non-passive lithium transport, then
• (b) contacting said cells with an effective amount of at least one labeled cellular building block;
• for a time sufficient to allow at least about 20% of the cell population to move from G1 phase to DNA synthesis phase, but not so long as to allow substantially all of the cell population to move from G1 phase to DNA synthesis phase, and thereafter
• (c) measuring the incorporation of labeled building block into said cells, relative to the incorporation of labeled building block into said cells when subjected to at least one of the following comparative conditions:
• (i) the same conditions, but in the absence of said compound, or
• (ii) the same conditions, including the presence of said compound, but in the absence of lithium ions, or
• (iii) the same conditions, in the presence of said compound, and in the presence of sodium ions instead of said lithium ions.

A method of identifying cell(s) or cell line(s) which express functional ligand-gated channels, said method comprising:

• measuring the incorporation of a labeled building block into said cell(s) or cell line(s) when said cell(s) or cell line(s) are contacted with lithium ions, relative to the incorporation of labeled building block into said cell(s) or cell line(s) when said cell(s) or cell line(s) are subjected to the same conditions, but in the absence of lithium ions;
• wherein the incorporation of said labeled building block into said cell(s) or cell line(s) is determined when said cell(s) or cell line(s) are first contacted with said compound and a lithium ion-containing flux buffer for a time sufficient to allow the intracellular accumulation of lithium, by both passive and non-passive means, but not so long as to allow the amount of passive lithium accumulation to substantially exceed the amount of non-passive lithium transport, and
• wherein said cell(s) or cell line(s) are thereafter contacted with an effective amount of at least one labeled cellular building block;
• for a time sufficient to allow at least about 20% of the cell population to move from G1 phase to DNA synthesis phase, but not so long as to allow substantially all of the cell population to move from G1 phase to DNA synthesis phase.

A method of identifying cell(s) or cell line(s) which express functional ligand-gated channels, said method comprising:

• (a) contacting said cell(s) or cell line(s) with a lithium ion-containing flux buffer for a time sufficient to allow the intracellular accumulation of lithium, by both passive and non-passive means, but not so long as to allow the amount of passive lithium accumulation to substantially exceed the amount of non-passive lithium transport, then
• (b) contacting said cells with an effective amount of at least one labeled cellular building block;
• for a time sufficient to allow at least about 20% of the cell population to move from G1 phase to DNA synthesis phase, but not so long as to allow substantially all of the cell population to move from G1 phase to DNA synthesis phase, and thereafter
• (c) measuring the incorporation of labeled building block into said cell(s) or cell line(s), relative to the incorporation of labeled building block into said cell(s) or cell line(s), when said cell(s) or cell line(s) are subjected to the same conditions, but in the absence of lithium ions.

A method to simultaneously determine if a compound is, directly or indirectly, an agonist or antagonist for ligand-gated channels contained on a cell, and if said compound has a non-specific effect on the metabolism of said cell, said method comprising:

• (a) measuring the incorporation of a labeled building block into said cell(s) or cell line(s), when said cell(s) or cell line(s) have been contacted with said compound and lithium ions, relative to the incorporation of labeled building block into said cell(s) or cell line(s) when said cell(s) or cell line(s) are subjected to substantially the same conditions, but in the presence of sodium ions instead of lithium ions;
• wherein the incorporation of said labeled building block into said cell(s) or cell line(s) is determined when said cell(s) or cell line(s) are first contacted with said compound and either:
• a lithium ion-containing flux buffer, or
• a sodium ion-containing flux buffer,
• wherein said contacting of said cell(s) or cell line(s) with said compound and lithium or sodium ions is carried out for a time sufficient to allow the intracellular accumulation of lithium or sodium, by both passive and non-passive means, but not so long as to allow the amount of passive lithium or sodium accumulation to substantially exceed the amount of non-passive lithium or sodium transport,
• wherein said cell(s) or cell line(s) are thereafter contacted with an effective amount of at least one labeled cellular building block, and
• wherein contacting of said cell(s) or cell line(s) with said labeled cellular building block is carried out for a time sufficient to allow at least about 20% of the cell population to move from G1 phase to DNA synthesis phase, but not so long as to allow substantially all of the cell population to move from G1 phase to DNA synthesis phase;
• and thereafter
• (b) comparing the incorporation of said labeled building block into said cell(s) or cell line(s) when exposed to the presence of lithium ions, relative to the incorporation of labeled building block into said cell(s) or cell line(s) when said cell(s) or cell line(s) are exposed to sodium ions instead of lithium ions.