Insect cardioactive peptides: cardioacceleratory peptide (CAP) activity is blocked in vivo and in vitro with a monoclonal antibody.

We demonstrate here that a specific monoclonal antibody can be utilized as a physiological tool to analyze neuropeptide function. Two cardioacceleratory peptides (CAPs) have been recently isolated from the CNS of the tobacco hawkmoth, Manduca sexta (Tublitz and Truman, 1985a), and it has been suggested that they act as cardioregulatory neurohormones during adult emergence and wing inflation (Tublitz and Truman, 1985b). Evidence is presented here indicating that a monoclonal antibody, 6C5, selectively and specifically precipitated the biological activities of both CAPs. In vivo injections of 6C5 markedly reduced CAP hemolymph titers in newly emerged adults. The 6C5 treatment also blocked the primary physiological effect of the CAPs, the increase in cardiac activity seen during adult wing expansion. In addition, removal of the postemergence CAP pulse with 6C5 prolonged the duration of wing-inflation behavior. Thus, by neutralizing CAP hemolymph activity with a CAP-specific antibody, we have shown that the CAPs are involved in cardioregulation in newly emerged moths.