Octopamine-like immunoreactivity in the honey bee and cockroach: Comparable organization in the brain and subesophageal ganglion

TLDR

The study aims to explore how octopamine may contribute to sensory integration and associative functions in honey bees and cockroaches. The octopaminergic processes arise from an ascending axon of a dorsal unpaired median neuron in the maxillary segment of the subesophageal ganglion. Octopamine-like immunoreactivity in both species reveals comparable, region‑specific neuronal distributions, with dense innervation of the protocerebral bridge, ellipsoid body, and selective mushroom body lobes, and distinct patterns in antennal lobes and subesophageal ganglion.

Abstract

A serum raised against octopamine reveals in cockroaches and honey bees structurally comparable systems of perikarya and their extensive yet discrete systems of arborizations in neuropils. Numerous and prominent clusters of lateral cell bodies in the brain as well as many midline perikarya provide octopamine-like immunoreactive processes to circumscribed regions of the subesophageal ganglion, antennal lobe glomeruli, optic neuropils, and neuropils of the protocerebrum. There is dense octopaminergic innervation in the protocerebral bridge and ellipsoid body of the central complex. The antennal lobes are supplied by at least three octopamine-immunoreactive neurons. In contrast, the mushroom bodies show the fewest immunoreactive elements. In Apis a single axon supplies sparse immunoreactive processes to the calyces' basal ring, collar, and lip. A diffuse arrangement of immunoreactive processes invades all zones of the mushroom body calyces in Periplaneta. These processes derive from an ascending axon ascribed to a dorsal unpaired median neuron at the maxillary segment of the subesophageal ganglion. In both taxa octopamine-immunoreactive processes invade only the gamma lobes of the mushroom bodies, omitting their other divisions. The present observations are discussed with respect to possible roles of octopamine in sensory integration and association.