Parturition hormone in the tsetse Glossina morsitans: activity in reproductive tissues from other species and response of tsetse to identified neuropeptides and other neuroactive compounds

Parturition hormone (PH) activity is present not only in the uterus of the tsetse Glossina morsitans but also in the oviducts of Bombyx mori and Schis tocerca gregaria, as well as the: ejaculatory duct of S. gregaria males. Ac tivity thus appears to be present in the reproductive ducts of diverse inse ct taxa. To determine whether any of the common insect neuropeptides are ca pable of mimicking the effect of PH, 35 identified neuropeptides and analog s were evaluated for PH activity. Modest PH activity was observed for only high doses of proctolin and a pyrokinin analog, thus suggesting that PH is unlikely to be closely related to any of the identified neuropeptides teste d. While proctolin was highly effective in stimulating contractions of the S. gregaria oviduct, the extract from the tsetse uterus elicited only a wea k response in this bioassay. PH activity was, however, effectively mimicked with an injection df 8 bromo-cyclic GMP, thus suggesting a potential role for this cyclic nucleotide in mediating the PH response. Pregnant females w ere responsive to PH, other neuropeptides and cyclic nucleotides only when females were neck-ligated. In intact females, the brain can presumably over ride the stimulation provided by the active compounds. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.