SPECIES-SPECIFIC ACTION AND DISTRIBUTION OF TACHYKININ-RELATED PEPTIDES IN THE FOREGUT OF THE COCKROACHES LEUCOPHAEA-MADERAE AND PERIPLANETA-AMERICANA

Nine tachykinin-related peptides (TRPs) have been isolated from the br ain and intestine of the cockroach Leucophaea maderae. In the present investigation, two of the nine TRPs, LemTRP 1 and 5, were tested for t heir ability to stimulate contractions in the foregut of the cockroach es L. maderae and Periplaneta americana in vitro. The two LemTRPs and the related locust peptide locustatachykinin I (LomTK I) induced contr actions in the foregut of P. americana in a dose-dependent manner, but had no myostimulatory action in L.maderae, A half-maximal response fo r the LemTRPs and LomTK I was obtained at 5x10(-9) mol l(-1). In both species, the neuropeptide proctolin stimulated foregut contractions. U sing an antiserum to LomTK I, we demonstrated that in both species the re are LomTK-like-immunoreactive (LomTK-LI) cell bodies and fibers wit hin the ganglia and nerves of the stomatogastric nervous system. Howev er, correlated with the species-specific action of the TRPs, we found efferent LomTK-LI nerve fibers supplying muscle fibers in the foregut of P. americana, but not in L. maderae. In both cockroach species, the re is a rich supply of proctolin-immunoreactive fibers to the foregut muscle. Some of the LomTK-LI fibers supplying the P. americana foregut muscle contain co-localized proctolin immunoreactivity, These fibers appear to be derived from a large cell body in the frontal ganglion wh ich also displayed co-localized immunoreactivities. Since TRP-containi ng neurons are restricted to the nerves and ganglia of the stomatogast ric nervous system both in P. americana and L.maderae, TRPs may be inv olved in the control of foregut movements in both species, but in P. a mericana the control may be more complex with the additional periphera lly projecting LomTK-LI neurons.