LOCALIZATION OF BURSICON IN CCAP-IMMUNOREACTIVE CELLS IN THE THORACICGANGLIA OF THE CRICKET GRYLLUS-BIMACULATUS

Bursicon is a neuropeptide that induces tanning of the cuticle in fres hly moulted insects, In an earlier investigation, we demonstrated that bursicon activity can be detected throughout the ventral nerve cord o f the cricket Gryllus bimaculatus. This study aims at identifying the neurosecretory cells within the thoracic ganglia that produce bursicon , When homogenates of anterior pieces of thoracic ganglia were separat ed using SDS gel electrophoresis, proteins with bursicon activity coul d be eluted only from a slice of the gel spanning the 28-33 kDa region , In the anterior lateral cortex of the thoracic ganglia, there are tw o bilaterally paired neurosecretory cells with large vacuoles that pro ject contralaterally to neurohaemal release sites associated with segm ental nerves N5 and N6. These cells and their processes in N5 and N6 w ere labelled using antisera against crustacean cardioactive peptide (C CAP), The cell projecting into N6 showed a Tyndall effect (i.e. appear ed opaque under oblique illumination) in older adults, and single isol ated somata contained bursicon activity, Homogenates of nerves N5 and N6 also showed bursicon activity, but neither bursicon activity nor CC AP-immunoreactive processes were found in segmental nerve N4. The thor acic connectives, which contain three major CCAP-immunoreactive proces ses, also showed bursicon activity, Homogenates of posterior pieces of the thoracic ganglia did not contain bursicon activity, Western blots demonstrated that the anti-CCAP serum does not recognize the 30 kDa b ursicon-active protein fraction, These results suggest that a CCAP-lik e neuropeptide and a protein with bursicon activity are co-localized i n the anterior lateral neurosecretory cells of the thoracic ganglia an d in their segmental homologues in the other ganglia, Additionally, we have shown using western blots that a monoclonal antibody raised agai nst a 56 kDa protein from the housefly Musca domestica, a protein thou ght to be bursicon, does not label the 30 kDa bursicon-active protein of crickets, However, this antibody does label an unidentified 56 kDa protein isolated from anterior as well as posterior pieces of thoracic ganglia.