Effects of diphenylhydantoin (DPH) on distal colon motility.

Diphenylhydantoin (DPH) induced changes in distal colon motility in the 37 subjects investigated. In subjects with sigmoidal hyperactivity plus rectal hypoactivity, DPH suppressed or reduced sigmoidal phasic activity. In subjects showing no sigmoidal activity predominance, DPH induced increases of sigmoidal and/or rectal motility. Sulpiride (an "atypical" dopaminergic blocking agent) antagonized DPH-induced changes. Our results strongly suggest that DPH-induced distal motility changes are mediated by the dopaminergic and noradrenergic systems.