Photoreceptors can transmit minute changes in voltage to photosynaptic cells over a wide range of background light intensities. Knowledge of the processes and molecule; involved in normal synaptic transmission from these specialized cells is essential if we wish to know how they might be altered in degeneration and disease. We have developed a prepartion, from an invertebrate, consisting-of huge photoreceptors with giant presynaptic terminals and recognizable postsynaptic cells, and have identified the photoreceptors' neurotransmitter as histamine. The particular advantages of this preparation will be exploited to study cellular processes, particularly those of transmitter dynamics, less easily approached in vertebrate photoreceptors. We will follow the fate of transmitter molecules with LM and EM autoradiography control and record the voltage from pre- and postsynaptic cells with electrophysiological methods and follow changes in intracellular calcium concentration using highspeed optical recording. The following questions will be addressed: (1) How does the reuptake of released transmitter contribute to synaptic function, in particular signal transfer? How is uptake into photoreceptors regulated, especially in a cell that releases transmitter continuously as this one does, and what role is played by uptake into glial cells at this synapse? (2) How does the synthesis of transmitter contribute to synaptic function and how is it regulated? (3) Is transmitter released in a quantal fashion from this synapse or by a carrier, and where is it stored? (4) Can we control the internal milieu of these terminals and in this way attempt to dissect out the steps in the release process?

National Institute of Health (NIH)
National Eye Institute (NEI)
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Visual Sciences C Study Section (VISC)
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University of North Carolina Chapel Hill
Schools of Medicine
Chapel Hill
United States
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Stuart, Ann E; Borycz, J; Meinertzhagen, Ian A (2007) The dynamics of signaling at the histaminergic photoreceptor synapse of arthropods. Prog Neurobiol 82:202-27
Stuart, Ann E; Gebhardt, Kelley A; Vogel, Stacy N et al. (2002) Does the neurotransmitter transporter underlie adaptation at a histaminergic photoreceptor synapse? Vis Neurosci 19:307-19
Stuart, Ann E; Mekeel, Harold E; Kempter, Elizabeth (2002) Uptake of the neurotransmitter histamine into the eyes of larvae of the barnacle (Balanus amphitrite). Biol Bull 202:53-60
Morgan, J R; Gebhardt, K A; Stuart, A E (1999) Uptake of precursor and synthesis of transmitter in a histaminergic photoreceptor. J Neurosci 19:1217-25
Stuart, A E; Morgan, J R; Mekeel, H E et al. (1996) Selective, activity-dependent uptake of histamine into an arthropod photoreceptor. J Neurosci 16:3178-88
Callaway, J C; Lasser-Ross, N; Stuart, A E et al. (1993) Dynamics of intracellular free calcium concentration in the presynaptic arbors of individual barnacle photoreceptors. J Neurosci 13:1157-66
Hayashi, J H; Stuart, A E (1993) Currents in the presynaptic terminal arbors of barnacle photoreceptors. Vis Neurosci 10:261-70
Battelle, B A; Calman, B G; Andrews, A W et al. (1991) Histamine: a putative afferent neurotransmitter in Limulus eyes. J Comp Neurol 305:527-42
Stuart, A E; Callaway, J C (1991) Histamine: the case for a photoreceptor's neurotransmitter. Neurosci Res Suppl 15:S13-23
Gwilliam, G F; Stuart, A E (1990) Characteristics of neurones projecting from the supraoesophageal ganglion in the shadow reflex pathway of the barnacle. J Exp Biol 151:83-107

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