An object of the present invention is to provide a remedy for dysfunction
of central monoamine pathway, a method for screening a PTP.zeta.
inhibitor or activator, which is useful as a remedy for gastric ulcer
caused by Helicobacter pylori or pleiotrophin which is a heparin-binding
secretory protein, and a non-human model animal being hyposensitive to a
stimulant drug, VacA which is a toxin of Helicobacter pylori, or
pleiotrophin by utilizing the physiological function of PTP.zeta.. After
administering a subject material to PTP.zeta. knockout mice and wild-type
mice, PTP.zeta. activity in the PTP.zeta. knockout mice and the wild-type
mice is compared and evaluated to screen a PTP.zeta. inhibitor or
activator. Examples of the comparison and the evaluation of the PTP.zeta.
activity include the comparison and the evaluation of the function of
central monoamine pathway such as changes in the level of central
monoamine metabolism, sensitivity to a stimulant drug, the presence of
dysfunction of mesolimbic dopamine pathway, level of acclimation to new
circumstances, or stress-responsiveness, and the comparison and the
evaluation of the level of binding to VacA, a toxin of Helicobacter
pylori, or pleiotrophin.