tachykinin stimulates 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 α-amylase, 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. tachykinin-ir 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 tachykinin-ir 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 α-amylase, protease and lipase activities while the buffer remained ineffective. tachykinin injection into the hemocoel increased α-amylase, 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.