Amine and amino acid transmitters in the eye of the mollusc Bulla gouldiana: an immunocytochemical study.

We identified putative transmitters of the photoreceptors and circadian pacemaker neurons and found candidates for efferent control in the eye of the marine mollusc Bulla gouldiana. Established antisera against octopamine, dopamine, serotonin, histamine, glutamate, gamma-aminobutyric acid (GABA), and taurine were used, and central ganglia were processed in parallel to evaluate general staining quality. Photoreceptors and circadian pacemaker cells both expressed immunoreactivity for glutamate and taurine. The eye and its sheath were devoid of GABA-like immunoreactive material, and none of the antisera directed against biogenic amines labelled cells or processes in the nervous tissue of the eye. However, dopamine and octopamine antisera stained large spherical granules (diameter 2-3 microm) contained in granular cells that are located in the connective tissue encapsulating the eye and the optic nerve. The serotonin antiserum revealed a sparse distribution of varicose axon fibers in the optic nerve and eye sheath. No histamine-immunoreactive processes were revealed in the eye. The functional significance of these findings for the molluscan eye and its circadian clock is discussed. Copyright 2000 Wiley-Liss, Inc.