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. <IMAGE>
METHOD OF SCREENING PTP ZETA ACTIVITY PROMOTER OR INHIBITOR