Referee 2's Review (Peter Gillespie):

This manuscript shows clearly that isolated Merkel cells respond with Ca2+ transients to hypo-osmotic stimuli, suggesting but not proving that these cells are indeed directly mechanically sensitive. The speed of the osmotic response is impressive compared to a standard volumetric regulation response. While whether the osmotic response really is an in vitro stand-in for a "real" touch response or not is debatable, it does allow a reproducible assay to look for inhibitors and for mediators of the response. Information gleaned from such studies could be used in intact preparations to prove mechanisms of Merkel cell-mediated touch transduction.

I have one major comment:

In my understanding, "hypotonic" refers to a solution with low electrolytes, not low osmotic strength. Throughout the manuscript, it is more appropriate to refer to "hypo-osmotic" solutions, not "hypotonic ones." For example the modified Ringers' solution described is isotonic with the "30% hypotonic" solution -- they have the same electrolyte concentrations.

Referring directly to the PLoS ONE criteria:

1. Are the experiments, statistics, and other analyses performed to a sufficient technical standard?
Yes, absolutely.

2. Are the conclusions presented in an appropriate fashion with speculations and hypotheses identified as such?
Yes.

3. Have the techniques used been documented in sufficient detail to allow replication?
Yes.

4. Is the report presented in an intelligible fashion and written in English?
Extremely well written.

5. Have the exact results reported been published elsewhere?
No.

6. Does the research meet all applicable standards with regard to the ethics of human / animal experimentation, participants' consent, and research integrity? Please contact us if you have any concerns.
No concerns.

7. Has the report adhered to the relevant community standards for research conduct, presentation of results, and deposition of data, where appropriate?
Yes.

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N.B. These are the comments made by the referee when reviewing an earlier version of this paper. Prior to publication the manuscript has been revised in light of these comments and to address other editorial requirements.