Differences between deep pain responses to hypertonic and hypotonic saline solutions

Different concentrations of both hypertonic and hypotonic aqueous sodium chloride solutions (0.2 ml) were injected into 24 hypodermic needles inserted in the gluteus medius muscles of 12 human subjects. It was found that a) both duration and intensity of deep pain responses were related to sodium chloride concentration; b) both latency and duration of pain responses were significantly greater with hypertonic than with hypotonic saline solutions; and c) hypertonic saline tended to induce subjective reports of a diffuse, dull ache, whereas hypotonic saline produced descriptions of a sharp, pricking, and well-localized pain. Submitted on April 3, 1962