The effects of crustacean cardioactive peptide on locust oviducts are calcium-dependent.
The role of calcium as a second messenger in the crustacean cardioactive peptide (CCAP)-induced contractions of the locust oviducts was investigated. Incubation of the oviducts in a calcium-free saline containing, a preferential calcium cation chelator, or an extracellular calcium channel blocker, abolished CCAP-induced contractions, indicating that the effects of CCAP on the oviducts are calcium-dependent. In contrast, sodium free saline did not affect CCAP-induced contractions. Co-application of CCAP to the oviducts with preferential L-type voltage-dependent calcium channel blockers reduced CCAP-induced contractions by 32-54%. Two preferential T-type voltage-dependent calcium channel blockers both inhibited CCAP-induced oviduct contractions although affecting different components of the contractions. Amiloride decreased the tonic component of CCAP-induced contractions by 40-55% and flunarizine dihydrochloride decreased the frequency of CCAP-induced phasic contractions by as much as 65%, without affecting tonus. Flunarizine dihydrochloride did not alter the proctolin-induced contractions of the oviducts. Results suggest that the actions of CCAP are partially mediated by voltage-dependent calcium channels similar to vertebrate L-type and T-type channels. High-potassium saline does not abolish CCAP-induced contractions indicating the presence of receptor-operated calcium channels that mediate the actions of CCAP on the oviducts. The involvement of calcium from intracellular stores in CCAP-induced contractions of the oviducts is likely since, an intracellular calcium antagonist decreased CCAP-induced contractions by 30-35%.
Donini
Andrew
A
Department of Zoology, University of Toronto at Mississauga, 3359, Mississauga Road North, L5L 1C6, Mississauga, Ontario, Canada. adonini@credit.erin.utoronto.ca
Lange
Angela B
AB
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D003035:Cobalt / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D005260:Female; D006110:Grasshoppers / Q000187:drug effects / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009479:Neuropeptides / Q000494:pharmacology*; D010057:Oviducts / Q000187:drug effects / Q000378:metabolism
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002614:Chelating Agents; D009479:Neuropeptides; C058620:crustacean cardioactive peptide; D003035:Cobalt; D004533:Egtazic Acid; C018021:cobaltous chloride; D002118:Calcium