The association of crustacean cardioactive peptide with the spermatheca of the African migratory locust, Locusta migratoria. 
Crustacean cardioactive peptide (CCAP)-like immunoreactivity was identified in neurons of the VIIIth abdominal ganglion and in axons in the nerves that project to the spermatheca of 3-4 week old adult female locusts.  In addition, lightly stained CCAP-like immunoreactive processes were localized over the spermathecae.  The amount of CCAP in the spermathecal tissue was quantified using an enzyme-linked immunosorbent assay (ELISA) performed on extracts of the whole spermatheca, and on its constituent parts, namely the sperm sac, coiled duct and straight duct.  The spermatheca contains 920+/-273 fmol (mean+/-SE) of CCAP equivalents, with the majority localized in the coiled duct.  There are age-related differences in the amount of CCAP present in the spermathecae with less content in spermathecae from 1 to 5 day old and greater content in spermathecae from 3 to 4 week old adults.  There was also no difference in CCAP content of spermathecae in mated and virgin 3 to 4 week old adults.  Reversed phase-high performance liquid chromatography (RP-HPLC) followed by ELISA further confirmed the presence of CCAP-like material in extracts of locust spermathecae.  Physiological assays demonstrated that CCAP increased the basal tonus and frequency of spontaneous contractions of the spermatheca, with thresholds between 10(-10) and 10(-9)M and maxima at 10(-7)M CCAP.  CCAP also increases the amplitude of neurally evoked contractions with a threshold less than 10(-11)M and a maximum of 10(-7)M CCAP.  The present study suggests that CCAP acts as a neuromodulator/neurotransmitter at the spermathecal visceral tissue of female Locusta migratoria.