PKA activity in the antennal lobe of honeybees is regulated by chemosensory stimulation in vivo

Abstract

The involvement of cyclic nucleotide cascades has been suggested for chemosensory signal processing as well as synaptic plasticity. Cyclic AMP-dependent protein kinase (PKA) is a major mediator for transient changes in these second messengers. The objective of this study was to examine the role of PKA in the central processing of chemosensory information by the honeybee. Effects of chemosensory stimulation in vivo were detected in the first chemosensory neuropil of the honeybee brain, the antennal lobe (AL), by using a combination of shock freezing and specific determination of PKA activity. Mechanosensory or odor stimulation of the antennae had no effect on PKA activity. Brief application of aqueous solutions (pure water or sucrose solution) to an antenna caused a rapid and transient elevation of PKA activity in the ipsilateral AL. A series of such stimuli led to a graded increase in PKA activity followed by a rapid decrease during the first 10 s after the end of stimulation, but elevated levels of PKA activity were observed for as long as 1 min. These results suggest that PKA activity and its regulation contribute to central processing of chemosensory signals.