Mushroom body feedback interneurones in the honeybee show GABA-like immunoreactivity

The distribution of the transmitter substance GABA was investigated in the mushroom body neuropile of the honeybee by means of immunohistochemistry. The protocerebro-calycal tract (PCT) links a mushroom body output area with the calycal input sites. Interneurones contained within the PCT exhibit GABA-like immunoreactivity and may function as negative feedback loop.