p-Chlorophenylalanine treatment depresses the number of synaptic ribbon profiles in the rat pineal gland, but does not abolish their day-night rhythm

Various organelles in the lamina terminals of housefly photoreceptors exhibit daily rhythms having a circadian basis. These include changes in the numbers of photoreceptor tetrad and L2 feedback synapses, and longitudinal movements of screening pigment. Circadian information has previously been suggested to spread from the clock to the lamina via widefield cells expressing either 5-hydroxytryptamine or pigment-dispersing hormone-like immunoreactivity. We examined the action of these neuromodulators, and other candidate neurotransmitters, 4 h after injecting either the transmitter or a control into the medulla. We counted electron microscope profiles of organelles that normally exhibit circadian changes, and two types of invagination into photoreceptor terminals, capitate projections and inter-receptor invaginations. No single substance mediated the changes observed. Injected pigment-dispersing hormone peptide decreased the number of pigment granules, implicating this peptide in screening pigment migration, but produced no changes in synapse-related organelles. alpha-Aminobutyric acid exclusively decreased the number of L2 feedback synapses. Responses to other transmitters were specific, and often large, but generally not statistically significant. Histamine, for example, may decrease the number of tetrads, possibly by direct autoregulation. The results suggest that there is likely to be more than one effector in the circadian pathways to the lamina.

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Neurotransmitters alter the numbers of synapses and organelles in photoreceptor terminals in the lamina of the housefly, Musca domestica

Pyza

Meinertzhagen

1998

Journal of Comparative Physiology A: Sensory, Neural, and Behav

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Presynaptic bodies (”ribbons"): from ultrastructural observations to molecular perspectives

Wagner

1997

Cell and Tissue Research

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The morphological diversity and dynamic aspects of presynaptic bodies are summarised. Molecular characteristics of the presynaptic machinery are discussed and the signals that control the plasticity of the presynaptic bodies are examined. A review is presented of recent findings regarding the physiology of tonically active synapses. The significance of the synaptic bodies and their dynamic changes in retinal and pineal photoreceptors are considered.

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p-Chlorophenylalanine treatment depresses the number of synaptic ribbon profiles in the rat pineal gland, but does not abolish their day-night rhythm

Cited by 2 publications

References 49 publications

Neurotransmitters alter the numbers of synapses and organelles in photoreceptor terminals in the lamina of the housefly, Musca domestica

Neurotransmitters alter the numbers of synapses and organelles in photoreceptor terminals in the lamina of the housefly, Musca domestica

Presynaptic bodies (”ribbons"): from ultrastructural observations to molecular perspectives

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