Biogenic amines in the brain of the honeybee, Apis mellifera

Fluorescence histochemistry with glyoxylic acid has been used in close conjunction with detailed anatomical studies (Mobbs 1982) to investigate the distribution of fluorogenic amines in the brain of the honeybee, Apis mellifera. In addition, the concentration and distribution of biogenic amines in the brain of the bee have been determined using highly sensitive radioenzymatic techniques and high performance liquid chromatography. The cerebral ganglia of the bee contain similar amounts of dopamine and serotonin, more dopamine than octopamine, and very low levels of noradrenaline. Slow fading green fluorescence, typical of catecholamines, was located throughout the cerebral ganglia, and was particularly intense in the central body and mushroom body neuropils. Results indicate that the fluorescence in the mushroom body neuropils is largely extrinsic in origin. Both dopamine and serotonin were detected in the calyces and alpha-lobe of the mushroom bodies, and in the antennal lobe. In the optic lobe, however, serotonin was found, but only low levels of dopamine were detected. Slow fading green fluorescence was replaced in the optic lobes by fluorescence which faded rapidly in the excitation light. The non-fluorogenic amine octopamine was found in the mushroom bodies and in the neuropils of the optic lobes, with the largest amounts of octopamine in the optic lobes associated with the neuropil of the medulla. The possibility that intrinsic neurones of the mushroom body neuropil are octopaminergic is discussed.