Octopamine in the locust brain: cellular distribution and functional significance in an arousal mechanism.

This review summarizes the distribution of octopamine-like immunoreactive neurons in the brain of the locust and the functional significance of a subset of them in an arousal mechanism in the visual system. A small set of identifiable octopamine-immunoreactive neurons lies in the ventromedial brain. Their cell bodies are large and readily accessible, which allows their removal and analysis of their biogenic amine content using gas-chromatography mass-spectrometry to confirm that they are genuinely octopaminergic. The neurons project from the central brain to the optic lobes where they arborize extensively in the medulla and lobula. There they release octopamine in response to multimodal input in the central brain. This evokes dishabitution in the locust's movement-detection system, suggesting an arousal mechanism.