Tachykinin stimulates effects on α-amylase, protease and lipase activities in the midgut of the American cockroach, Periplaneta americana (Blattodea: Blattidae)

The effect of a neuropeptide, the tachykinin on αamylase, protease and lipase activities in the midgut of American cockroach, Periplaneta americana (Linnaeus) is evaluated . Immunohistochemical reactivities against tachykinin (tachykinin ir) were detected in the midgut. Tachykininir cells in three regions (anterior, median and posterior) of the midgut were counted in normally fed, starved for four weeks and refed cockroaches. The number of tachykininir cells decreased during 4 weeks of starvation and increased 3 h after refeeding. The results of the competitive ELISA were consistent with the profile of immunohistochemical reactivity. Incubation of the dissected midgut with tachykinin led to an increase in αamylase, protease and lipase activities while the buffer remained ineffective. Tachykinin injection into the hemocoel increased αamylase, protease and lipase activities, but PBS injection showed no sign of effectiveness. The results seggest that nutrients upregulate midgut cells secreting tachykinin causing further activities of digestive enzymes.