GF MICE EXHIBIT SIGNIFICANTLY DECREASED LEVELS OF seRUM colonic 5-ht A n s ★★★ 1.25 3.0 1.00 生2 0.75 1.5 10 0.25 05 0.00 0. SPF GE PO P21 P42 Po P21 P42 P42 SPF GF PO P21 P42 PO P21 P42 P42 GF+CONV SPF+ABX VEH GF+CONV. SPF+ABX VEHGF MICE EXHIBIT SIGNIFICANTLY DECREASED LEVELS OF SERUM & COLONIC 5-HT