Frequency-Dependent Properties of Inhibitory Synapses in the Rostral Nucleus of the Solitary Tract

Grabauskas, Gintautas; Bradley, Robert M.

doi:10.1152/jn.00963.2001

Cited by 22 publications

(16 citation statements)

References 43 publications

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“…11) or the ability to follow two closely timed pulses (not shown). The efficacy of trains over single pulses has also been observed in the adjacent rNST (33,34,36). This may reflect the need for sustained neural activity from the rNST to activate RF circuitry, a mechanism similar to that proposed for solitary tract stimulation of the rNST (33).…”

Section: Technical Considerationsmentioning

confidence: 71%

“…For example, in vitro techniques have proved successful in analyzing local circuit connections between the caudal NST (cNST) and dorsal motor nucleus (DMN) of the vagus (13,21,22,79, 80). Although patch-clamp studies have begun to elucidate biophysical and synaptic properties of gustatory neurons in the rNST (8,9,11,33,35,36,77), the output of the rNST to the subjacent RF has not been studied.The present series of experiments was designed to determine whether populations of preoromotor neurons in the IRt receive inputs from the overlying solitary nucleus. We began with livecell confocal calcium imaging to determine whether a defined population of neurons within the RF, i.e., those that project to the hypoglossal nucleus (mXII), could be activated by electrical stimulation of the rNST.…”

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confidence: 99%

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Local circuit input to the medullary reticular formation from the rostral nucleus of the solitary tract

Nasse

Terman²,

Venugopal³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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The intermediate reticular formation (IRt) subjacent to the rostral (gustatory) nucleus of the solitary tract (rNST) receives projections from the rNST and appears essential to the expression of taste-elicited ingestion and rejection responses. We used whole cell patch-clamp recording and calcium imaging to characterize responses from an identified population of prehypoglossal neurons in the IRt to electrical stimulation of the rNST in a neonatal rat pup slice preparation. The calcium imaging studies indicated that IRt neurons could be activated by rNST stimulation and that many neurons were under tonic inhibition. Whole cell patch-clamp recording revealed mono- and polysynaptic projections from the rNST to identified prehypoglossal neurons. The projection was primarily excitatory and glutamatergic; however, there were some inhibitory GABAergic projections, and many neurons received excitatory and inhibitory inputs. There was also evidence of disinhibition. Overall, bath application of GABA(A) antagonists increased the amplitude of excitatory currents, and, in several neurons, stimulation of the rNST systematically decreased inhibitory currents. We have hypothesized that the transition from licks to gapes by natural stimuli, such as quinine monohydrochloride, could occur via such disinhibition. We present an updated dynamic model that summarizes the complex synaptic interface between the rNST and the IRt and demonstrates how inhibition could contribute to the transition from ingestion to rejection.

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Section: Technical Considerationsmentioning

confidence: 71%

mentioning

confidence: 99%

Local circuit input to the medullary reticular formation from the rostral nucleus of the solitary tract

Nasse

Terman²,

Venugopal³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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“…In some types of synapses, repeated stimulation results in a buildup of a tonic component through mechanisms such as asynchronous release or transmitter accumulation in the synaptic cleft (Eccles et al 1966;Grabauskas and Bradley 2003;Lu and Trussell 2000;Scanziani et al 1997). Such a residual charge would affect synaptic computation and spike train transformation at the MNTB in a different way than phasic, fast-decaying IPSPs would do.…”

Section: Residual Chargementioning

confidence: 99%

Glycinergic inhibition to the medial nucleus of the trapezoid body shows prominent facilitation and can sustain high levels of ongoing activity

Mayer

Albrecht

Dondzillo

et al. 2014

Journal of Neurophysiology

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tion to the medial nucleus of the trapezoid body shows prominent facilitation and can sustain high levels of ongoing activity. J Neurophysiol 112: 2901-2915. First published September 3, 2014 doi:10.1152/jn.00864.2013.-Neurons in the medial nucleus of the trapezoid body (MNTB) are well known for their prominent excitatory inputs, mediated by the calyx of Held. Less attention has been paid to the prominent inhibitory inputs that MNTB neurons also receive. Because of their auditory nature, both excitatory and inhibitory synapses are highly active in vivo. These high levels of activity are known to reduce excitatory synaptic currents considerably, such that in vivo synaptic currents produced by the calyx are smaller than typically measured in standard brain slice experiments. The goal of this study was to investigate the properties of the inhibitory inputs in the Mongolian gerbil (Meriones unguiculatus) under activity levels that correspond to those in the intact brain to facilitate a direct comparison between the two inputs. Our results suggest that inhibitory inputs to MNTB are largely mediated by a fast and phasic glycinergic component, and to a lesser degree by a GABAergic component. The glycinergic component can sustain prolonged high levels of activity. Even when challenged with stimulus patterns consisting of thousands of stimuli over tens of minutes, glycinergic inputs to MNTB maintain large conductances and fast decays and even facilitate substantially when the stimulation frequency is increased. The inhibition is mediated by a relatively small number of independent input fibers. The data presented here suggest that inhibitory inputs to MNTB sustain high levels of activity and need to be considered for a full understanding of mechanisms underlying processing of auditory information in MNTB. auditory brain stem; inhibition; medial nucleus of the trapezoid body; calyx of Held; short-term plasticity SYNAPTIC TRANSMISSION in the medial nucleus of the trapezoid body (MNTB) has been studied extensively over the last years. Principal neurons in the MNTB receive neural excitation via a giant synapse, the calyx of Held (Borst et al. 1995;Borst and Soria van Hoeve 2012;Forsythe 1994;Held 1892Held , 1893Tolbert et al. 1982). Synaptic currents produced by the calyx are large and fast, and both the calyx and the postsynaptic neuron have a number of adaptations suited to transmit action potentials with very high temporal fidelity (Guinan and Li 1990;Kochubey et al. 2009;Taschenberger and von Gersdorff 2000). Besides temporal precision, it has been argued that one reason for the large excitatory signals is that the calyx of Held/MNTB system is a fail-safe relay station that simply converts glutamatergic excitation into glycinergic inhibition without any significant spike train transformation (Borst and Soria van Hoeve 2012;Crins et al. 2011;McLaughlin et al. 2008;Smith et al. 1998;Taschenberger and von Gersdorff 2000). The sign inversion is needed because neural inhibition is required in the sound localization process i...

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“…Most of the afferent fibers involved in the control of cardiovascular and respiratory functions terminate around the obex and caudal to it (2), in the subpostremal NTS (3). Although there are a large variety of neurotransmitters and neuromodulators within the NTS, glutamate and GABA are considered to be the principal neurotransmitters (4)(5)(6). It is accepted that glutamate is the neurotransmitter released by the first-order visceral afferent fibers (6,7) and that it acts on N-methyl-D-aspartate (NMDA) and non-NMDA ionotropic receptors in second-order neurons within the NTS (5,8).…”

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confidence: 99%

Electrophysiological evidence for the presence of NR2C subunits of N-methyl-D-aspartate receptors in rat neurons of the nucleus tractus solitarius

Baptista

Ogawa

Aguiar

et al. 2005

Braz J Med Biol Res

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The nucleus tractus solitarius (NTS) plays an important role in the control of autonomic reflex functions. Glutamate, acting on N-methyl-D-aspartate (NMDA) and non-NMDA ionotropic receptors, is the major neurotransmitter in this nucleus, and the relative contribution of each receptor to signal transmission is unclear. We have examined NMDA excitatory postsynaptic currents (NMDA-EPSCs) in the subpostremal NTS using the whole cell patch clamp technique on a transverse brainstem slice preparation. The NMDA-EPSCs were evoked by stimulation of the solitary tract over a range of membrane potentials. The NMDA-EPSCs, isolated pharmacologically, presented the characteristic outward rectification and were completely blocked by 50 µM DL-2-amino-5-phosphonopentanoic acid. The I-V relationship of the NMDA response shows that current, with a mean (± SEM) amplitude of -41.2 ± 5.5 pA, is present even at a holding potential of -60 mV, suggesting that the NMDA receptors are weakly blocked by extracellular Mg 2+ at near resting membrane potentials. This weak block can also be inferred from the value of 0.67 ± 0.17 for parameter δ obtained from a fit of the Woodhull equation to the I-V relationship. The maximal inward current measured on the I-V relationship was at -38.7 ± 4.2 mV. The decay phase of the NMDA currents was fitted with one exponential function with a decay time constant of 239 ± 51 and 418 ± 80 ms at a holding potential of -60 and +50 mV, respectively, which became slower with depolarization (e-fold per 145 mV).

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Frequency-Dependent Properties of Inhibitory Synapses in the Rostral Nucleus of the Solitary Tract

Cited by 22 publications

References 43 publications

Local circuit input to the medullary reticular formation from the rostral nucleus of the solitary tract

Local circuit input to the medullary reticular formation from the rostral nucleus of the solitary tract

Glycinergic inhibition to the medial nucleus of the trapezoid body shows prominent facilitation and can sustain high levels of ongoing activity

Electrophysiological evidence for the presence of NR2C subunits of N-methyl-D-aspartate receptors in rat neurons of the nucleus tractus solitarius

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