Pinealocyte synaptic ribbons and neuroendocrine function

McNulty, John A.; Fox, Linda M.

doi:10.1002/jemt.1070210302

Cited by 29 publications

(19 citation statements)

References 68 publications

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“…Note that the shorter synaptic ribbon profiles predominate at noon, whereas longer profiles are conspicuous at midnight& / f i g . c : through SRs in the rat (King and Dougherty 1982a;McNulty and Fox 1992). The finding that in the rat pineal virtually all the SRs observed were plate-like should not be taken as evidence that this is also the case in other species.…”

Section: Discussionmentioning

confidence: 57%

“…In many studies a numerical increase of SR profiles under various physiological and experimental conditions has been described (Lues 1971;Karasek 1976;Vollrath 1981;Khaledpour and Vollrath 1987;Karasek et al 1988;Karasek 1992;McNulty and Fox 1992;Bhatnagar 1994). The nocturnal increase lies in the range between 2-and 6.7-fold (for review see McNulty and Fox 1992). According to our results approximately one-third of the nocturnal increase could be accounted for by the nocturnal enlargement of SRs.…”

Section: Discussionmentioning

confidence: 98%

“…King and Dougherty (1982a) assume that most, if not all, SRs are plate-like or discoid. McNulty and Fox (1992) distinguished ribbon-, rod-or plate-like SR r and a second population of spherical or punctate shape SR sp . Moreover, intermediate-type structures were observed.…”

Section: Introductionmentioning

confidence: 99%

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The shape of synaptic ribbons in the rat pineal gland

Jastrow

Mach

Vollrath

1997

Cell and Tissue Research

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Under the transmission electron microscope, synaptic ribbons (SRs) of the mammalian pineal gland appear as rod-like organelles. Their three-dimensional structure is not precisely known. In the present study, pineal SRs were investigated using serial sections obtained from rats killed at noon and midnight. The shape of the SRs was reconstructed based on SR profile length and the number of sections in which the profiles were contained. The results obtained show that SRs are basically flat plate-like structures with polymorphic lateral edges. Reconstructions of SRs revealed that they had average dimensions of 300x150x35 nm and were 19.3% larger at night than at day; the difference in SR size points to perhaps major differences in synaptic function between day and night.

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Section: Discussionmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 98%

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The shape of synaptic ribbons in the rat pineal gland

Jastrow

Mach

Vollrath

1997

Cell and Tissue Research

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“…In contrast, the RRP estimate from ⌬C m measurements in mouse inner hair cells is Ϸ53-64 SVs per synapse, whereas the morphologically docked SV pool contains only [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Some of this difference may be due to the fact that synaptic exocytosis had not been inhibited before fixation, which in frog saccular hair cells reduced the number of docked SVs per synapse from 43 to 32 (11).…”

Section: Discussionmentioning

confidence: 99%

Frequency selectivity of synaptic exocytosis in frog saccular hair cells

Rutherford

Roberts

2006

Proc. Natl. Acad. Sci. U.S.A.

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The ability to respond selectively to particular frequency components of sensory inputs is fundamental to signal processing in the ear. The frog (Rana pipiens) sacculus, which is used for social communication and escape behaviors, is an exquisitely sensitive detector of sounds and ground-borne vibrations in the 5-to 200-Hz range, with most afferent axons having best frequencies between 40 and 60 Hz. We monitored the synaptic output of saccular sensory receptors (hair cells) by measuring the increase in membrane capacitance (⌬Cm) that occurs when synaptic vesicles fuse with the plasmalemma. Strong stepwise depolarization evoked an exocytic burst that lasted 10 ms and corresponded to the predicted capacitance of all docked vesicles at synapses, followed by a 20-ms delay before additional vesicle fusion. Experiments using weak stimuli, within the normal physiological range for these cells, revealed a sensitivity to the temporal pattern of membrane potential changes. Interrupting a weak depolarization with a properly timed hyperpolarization increased ⌬Cm. Small sinusoidal voltage oscillations (؎5 mV centered at ؊60 mV) evoked a ⌬Cm that corresponded to 95 vesicles per s at each synapse at 50 Hz but only 26 vesicles per s at 5 Hz and 27 vesicles per s at 200 Hz (perforated patch recordings). This frequency selectivity was absent for larger sinusoidal oscillations (؎10 mV centered at ؊55 mV) and was largest for hair cells with the smallest sinusoidal-stimulievoked Ca 2؉ currents. We conclude that frog saccular hair cells possess an intrinsic synaptic frequency selectivity that is saturated by strong stimuli.afferent ͉ synaptic vesicle pool ͉ ribbon synapse ͉ capacitance ͉ tuning T he auditory and vestibular systems in the ear and the related mechanosensory and electrosensory organs of the lateral line employ a remarkable variety of mechanical and neural mechanisms to distinguish frequency components of sensory signals from Ͻ10 Hz to nearly 100 kHz (1, 2). In each of these organs, a sensory stimulus passes through one or more stages of mechanical or electrical filtering (3), leading to graded changes in the sensory receptor cell's membrane potential, V m . Oscillatory sensory stimuli usually produce oscillations in V m , with the greatest amplitude occurring at a preferred frequency. Hair cells in the frog sacculus possess a broadly tuned electrical filter that causes V m to oscillate preferentially at frequencies between 35 and 75 Hz (4), as well as spontaneous oscillations of the mechanosensory apparatus at frequencies between 5 and 50 Hz (5).At the hair cells' output synapses, the information contained in V m is transmitted by a chemical neurotransmitter (glutamate) to postsynaptic terminals and encoded as a train of action potentials that travel to the brain. Each of these afferent synapses contains a presynaptic dense body [also known as the synaptic body (SB) or synaptic ribbon] (Fig. 1a) similar to ribbon synapses in the retina. As at other chemical synapses, V m controls calcium influx through voltage-gated cal...

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“…Vollrath 1981). Well-known examples are the distinct rhythms of melatonin synthesis, of spontaneous electrical activity and of "synaptic" bodies probably involved in intercellular communication (for reviews, see McNulty and Fox 1992;Reuss 1987;Sugden 1989;Vollrath 1981;Vollrath and Spiwoks 1996). A considerable number of studies indicate that these rhythms are driven by the SCN and predominantly are mediated by the sympathetic system.…”

Section: Pineal Rhythms and Outputmentioning

confidence: 97%

Components and connections of the circadian timing system in mammals

Reuss

1996

Cell and Tissue Research

102

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The circadian timing system is a neural network consisting of the hypothalamic suprachiasmatic nucleus, aided by the retina, other hypothalamic nuclei, autonomic regions of the spinal cord, sympathetic ganglia and the pineal gland. Extensive studies conducted over the last two decades have unravelled the principal items of its functional neuroanatomy. The system is responsible for the generation of the circadian rhythm, its synchronization by environmental factors such as light, and its mediation with respect to morphological, physiological and biochemical parameters of mammals that exhibit distinct alterations throughout the 24-h cycle. This review characterizes the brain sites involved and the pathways responsible for the generation and maintenance of circadian rhythmicity.

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Pinealocyte synaptic ribbons and neuroendocrine function

Cited by 29 publications

References 68 publications

The shape of synaptic ribbons in the rat pineal gland

The shape of synaptic ribbons in the rat pineal gland

Frequency selectivity of synaptic exocytosis in frog saccular hair cells

Components and connections of the circadian timing system in mammals

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