THE ANTENNAL MOTOR SYSTEM OF CRICKETS - PROCTOLIN IN SLOW AND FAST MOTONEURONS AS REVEALED BY DOUBLE-LABELING

This study decribes proctolin-like immunoreactivity (PLI) of identifie d antennal motoneurons in the brain of adult crickets (Gryllus bimacul atus). The motoneurons were first backfilled with the fluorescent dye Lucifer Yellow and then immunohistochemically labelled with an antibod y against proctolin. Altogether 14 of the 17 excitatory antennal moton eurons, including physiologically fast and slow types, showed PLI. The only common inhibitor consistently demonstrated a weak positive PLI. PLI was also present in the dendritic arborizations and varicosities o f motor axons in the intrinsic antennal muscles. Densitometric measure ments of motoneuron somata showed significant differences in the inten sity of PLI in different types of antennal motoneurons, suggesting tha t antennal motoneurons produce different amounts of proctolin. Identic al motoneuron somata display a large variance of PLI intensities in di fferent brains. This observation may indicate up- and down-regulation of proctolin in individual crickets.