def ek(cell):
    """
    Returns the WT reversal potential (in mV) for the given integer index
    ``cell``.
    """
    reversal_potentials = {
        1: -91.6,
        2: -92.8,
        3: -95.1,
        4: -92.3,
        5: -106.1
    }
    return reversal_potentials[cell]