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Abstract
Crustacean cardioactive peptide (CCAP) stimulates the contractions of locust oviducts.
CCAP increased the basal tonus and increased the frequency and amplitude of phasic
contractions, as well as the amplitude of neurally-evoked oviduct contractions in
a dose-dependent manner. Oviducts from Vth instar larvae and adult locusts aged 10
days or less, were more sensitive to CCAP than oviducts from adult locusts aged 12
days or more. This may be indicative of a differential expression of number or subtypes
of CCAP receptors on the oviducts at different ages, and may be related to reproductive
functions or to functions of CCAP on the oviducts during ecdysis. The oviducts appear
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, however, the oviducts are more sensitive
to CCAP. No CCAP-like immunoreactive structures were discovered in the nerves innervating
the oviducts, or on the oviducts themselves, confirming the previously published suggestion
(Dircksen et al., 1991) that CCAP acts as a neurohormone at the oviducts. Cells showing
CCAP-like immunoreactivity were discovered in the fat body associated with the oviducts
and represent a potential source of CCAP, along with CCAP released from the transverse
nerve and perivisceral organs.