Crustacean cardioactive peptide is a modulator of oviduct contractions in Locusta migratoria

Crustacean cardioactive peptide (CCAP) stimulates the contractions of locus t oviducts. CCAP increased the basal tonus and increased the frequency and amplitude of phasic contractions, as well as the amplitude of neurally-evok ed oviduct contractions in a dose-dependent manner. Oviducts from Vth insta r larvae and adult locusts aged 10 days or less, were more sensitive to CCA P than oviducts from adult locusts aged 12 days or more. This may be indica tive of a differential expression of number or subtypes of CCAP receptors o n the oviducts at different ages, and may be related to reproductive functi ons or to functions of CCAP on the oviducts during ecdysis, The oviducts ap pear more sensitive to CCAP when compared with previously published reports of CCAP actions on the hindgut. CCAP actions on the amplitude of neurally- evoked contractions of the oviducts are similar to those of proctolin, howe ver. the oviducts are more sensitive to CCAP. No CCAP-like immunoreactive s tructures were discovered in the nerves innervating the oviducts, or on the oviducts themselves, confirming the previously published suggestion (Dirck sen et al., 1991) that CCAP acts as a neurohormone at the oviducts. Cells s howing CCAP-like immunoreactivity were discovered in the fat body associate d with the oviducts and represent a potential source of CCAP, along with CC AP released from the transverse nerve and perivisceral organs. (C) 2001 Els evier Science Ltd. All rights reserved.