scholarly journals What is transmitted in “synaptic transmission”?

2010 ◽  
Vol 34 (2) ◽  
pp. 115-116 ◽  
Author(s):  
Erik Montagna ◽  
Adriana M. S. de Azevedo ◽  
Camilla Romano ◽  
Ronald Ranvaud
Keyword(s):  
Action Potential ◽  
Synaptic Transmission ◽  
Presynaptic Terminal ◽  
Synaptic Integration ◽  
High Grade ◽  
Transmission Right ◽  
The Mind

Even students that obtain a high grade in neurophysiology often carry away a serious misconception concerning the final result of the complex set of events that follows the arrival of an action potential at the presynaptic terminal. The misconception consists in considering that “at a synapse, information is passed on from one neuron to the next” is equivalent to (and often expressed explicitly as) “the action potential passes from one neuron to the next.” More than half of four groups of students who were asked to comment on an excerpt from a recent physiology textbook that openly stated the misconception had no clear objection to the text presented. We propose that the first culprit in generating this misconception is the term “synaptic transmission,” which promotes the notion of transferring something or passing something along (implicitly unchanged). To avoid establishing this misconception, the first simple suggestion is to use words like “synaptic integration” rather than “synaptic transmission” right from the start. More generally, it would be important to focus on the function of synaptic events rather than on rote listing of all the numerous steps that are known to occur, which are so complex as to saturate the mind of the student.

scholarly journals The Mechanical Basis of Memory - the MeshCODE Theory

2020 ◽  
Author(s):  
Benjamin T. Goult
Keyword(s):  
Action Potential ◽  
Synaptic Transmission ◽  
Data Storage ◽  
Spike Trains ◽  
Binary Format ◽  
Potential Spike ◽  
Mechanical Basis ◽  
The Mind ◽  
And Storage ◽  
The Brain

The MeshCODE framework outlined here represents a unifying theory of data storage in animals, providing read/write storage of both dynamic and persistent information in a binary format. Mechanosensitive proteins, that contain force-dependent switches, can store information persistently which can be written/updated using small changes in mechanical force. These mechanosensitive proteins, such as talin, scaffold each and every synapse creating a meshwork of switches that forms a code, a MeshCODE. Synaptic transmission and action potential spike trains would operate the cytoskeletal machinery to write and update the synaptic MeshCODEs, propagating this coding throughout the brain and to the entire organism. Based on established biophysical principles, a mechanical basis for memory provides a physical location for data storage in the brain. Furthermore, the conversion and storage of sensory and temporal inputs into a binary format identifies an addressable read/write memory system supporting the view of the mind as an organic supercomputer.

scholarly journals Kv1.3 channels regulate synaptic transmission in the nucleus of solitary tract

2011 ◽  
Vol 105 (6) ◽  
pp. 2772-2780 ◽  
Author(s):  
Angelina Ramirez-Navarro ◽  
Patricia A. Glazebrook ◽  
Michelle Kane-Sutton ◽  
Caroline Padro ◽  
David D. Kline ◽  
...  
Keyword(s):  
Action Potential ◽  
Transmitter Release ◽  
Brain Slices ◽  
Presynaptic Terminal ◽  
Solitary Tract ◽  
Sensory Afferents ◽  
Peripheral Neurons ◽  
C Fibers ◽  
Nodose Ganglia ◽  
Nucleus Of Solitary Tract

The voltage-gated K+ channel Kv1.3 has been reported to regulate transmitter release in select central and peripheral neurons. In this study, we evaluated its role at the synapse between visceral sensory afferents and secondary neurons in the nucleus of the solitary tract (NTS). We identified mRNA and protein for Kv1.3 in rat nodose ganglia using RT-PCR and Western blot analysis. In immunohistochemical experiments, anti-Kv1.3 immunoreactivity was very strong in internal organelles in the soma of nodose neurons with a weaker distribution near the plasma membrane. Anti-Kv1.3 was also identified in the axonal branches that project centrally, including their presynaptic terminals in the medial and commissural NTS. In current-clamp experiments, margatoxin (MgTx), a high-affinity blocker of Kv1.3, produced an increase in action potential duration in C-type but not A- or Ah-type neurons. To evaluate the role of Kv1.3 at the presynaptic terminal, we examined the effect of MgTx on tract evoked monosynaptic excitatory postsynaptic currents (EPSCs) in brain slices of the NTS. MgTx increased the amplitude of evoked EPSCs in a subset of neurons, with the major increase occurring during the first stimuli in a 20-Hz train. These data, together with the results from somal recordings, support the hypothesis that Kv1.3 regulates the duration of the action potential in the presynaptic terminal of C fibers, limiting transmitter release to the postsynaptic cell.

Resting and Active Properties of Pyramidal Neurons in Subiculum and CA1 of Rat Hippocampus

2000 ◽  
Vol 84 (5) ◽  
pp. 2398-2408 ◽  
Author(s):  
Nathan P. Staff ◽  
Hae-Yoon Jung ◽  
Tara Thiagarajan ◽  
Michael Yao ◽  
Nelson Spruston
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Pyramidal Neurons ◽  
Current Injection ◽  
Synaptic Integration ◽  
Membrane Properties ◽  
Neuronal Membrane ◽  
Similar Action ◽  
Ca1 Neurons ◽  
Ca1 Pyramidal Neurons

Action potentials are the end product of synaptic integration, a process influenced by resting and active neuronal membrane properties. Diversity in these properties contributes to specialized mechanisms of synaptic integration and action potential firing, which are likely to be of functional significance within neural circuits. In the hippocampus, the majority of subicular pyramidal neurons fire high-frequency bursts of action potentials, whereas CA1 pyramidal neurons exhibit regular spiking behavior when subjected to direct somatic current injection. Using patch-clamp recordings from morphologically identified neurons in hippocampal slices, we analyzed and compared the resting and active membrane properties of pyramidal neurons in the subiculum and CA1 regions of the hippocampus. In response to direct somatic current injection, three subicular firing types were identified (regular spiking, weak bursting, and strong bursting), while all CA1 neurons were regular spiking. Within subiculum strong bursting neurons were found preferentially further away from the CA1 subregion. Input resistance ( R N), membrane time constant (τm), and depolarizing “sag” in response to hyperpolarizing current pulses were similar in all subicular neurons, while R N and τm were significantly larger in CA1 neurons. The first spike of all subicular neurons exhibited similar action potential properties; CA1 action potentials exhibited faster rising rates, greater amplitudes, and wider half-widths than subicular action potentials. Therefore both the resting and active properties of CA1 pyramidal neurons are distinct from those of subicular neurons, which form a related class of neurons, differing in their propensity to burst. We also found that both regular spiking subicular and CA1 neurons could be transformed into a burst firing mode by application of a low concentration of 4-aminopyridine, suggesting that in both hippocampal subfields, firing properties are regulated by a slowly inactivating, D-type potassium current. The ability of all subicular pyramidal neurons to burst strengthens the notion that they form a single neuronal class, sharing a burst generating mechanism that is stronger in some cells than others.

Histaminergic synaptic transmission in the cerebral ganglion of Aplysia

1985 ◽  
Vol 53 (4) ◽  
pp. 1016-1037 ◽  
Author(s):  
R. E. McCaman ◽  
D. Weinreich
Keyword(s):  
Action Potential ◽  
Synaptic Transmission ◽  
Voltage Clamp ◽  
Cerebral Ganglion ◽  
Major Influence ◽  
Electrical Synapses ◽  
Postsynaptic Potentials ◽  
Synaptic Potentials ◽  
Chemical Synapses ◽  
Synaptic Responses

Standard intracellular stimulating and recording techniques including voltage-clamp were used to analyze the synaptic responses mediated by two identifiable histamine-containing neurons (HCNs), designated C2 neurons, located in bilaterally symmetric clusters of the isolated cerebral ganglion of Aplysia california. Activation of each C2 induced unitary chemically mediated synaptic potentials in over 15 identified ipsilateral follower neurons. Several additional followers were connected to the HCNs by nonrectifying electrical synapses. Most of the follower neurons examined received only chemical synapses from the C2s. Some of the followers were reciprocally connected with each other through nonrectifying electrical synapses. A single C2 action potential can evoke six distinctive types of chemically mediated postsynaptic potentials (PSPs) in different follower neurons. Most of the PSPs have been shown to be multicomponent, i.e., they are comprised of various combinations of individual fast (less than or equal to 150 ms), slow (1-2 s), and very slow (greater than or equal to 4 s) depolarizing and hyperpolarizing components. The combination of these components produces PSPs of varying complexity, from simple monophasic responses such as the frequently observed slow excitatory PSPs and slow inhibitory PSPs to responses consisting of two to three components such as fast excitatory, slow inhibitory PSPs or fast inhibitory, slow excitatory PSPs. All of the multicomponent PSPs appear to be mediated through monosynaptic connections from the C2, as determined by various electrophysiological criteria. The slow and very slow synaptic components of the multicomponent PSPs were markedly potentiated in amplitude and duration after repetitive C2 activation. This property of the slow components permits the slower PSPs to exert a major influence on the excitability and integrative properties of the follower neurons.

Vesicular or Quantal and Subquantal Transmitter Release

Physiology ◽  
1994 ◽  
Vol 9 (2) ◽  
pp. 59-64 ◽  
Author(s):  
J Vautrin
Keyword(s):  
Synaptic Transmission ◽  
Transmitter Release ◽  
Alternative Hypothesis ◽  
Presynaptic Terminal ◽  
Individual Activity ◽  
Terminal Units

When quantal synaptic transmission was discovered four decades ago, elementary transmitter releases initially were assigned to individual activity of presynaptic terminal units. Soon after an alternative hypothesis was proposed: elementary transmitter packets are preformed in specialized vesicles and released by exocytosis. Although the latter representation largely prevails, data are not conclusive.

Synaptic Transmission with the Glia

Physiology ◽  
2001 ◽  
Vol 16 (4) ◽  
pp. 178-184 ◽  
Author(s):  
Sabino Vesce ◽  
Paola Bezzi ◽  
Andrea Volterra
Keyword(s):  
Synaptic Transmission ◽  
Glial Cells ◽  
Brain Function ◽  
Synaptic Integration ◽  
New Findings ◽  
The Brain

For decades, scientists thought that all of the missing secrets of brain function resided in neurons. However, a wave of new findings indicates that glial cells, formerly considered mere supporters and subordinate to neurons, participate actively in synaptic integration and processing of information in the brain.

Dynamics of sensory afferent synaptic transmission in aortic baroreceptor regions on nucleus tractus solitarius

1995 ◽  
Vol 74 (4) ◽  
pp. 1518-1528 ◽  
Author(s):  
M. C. Andresen ◽  
M. Yang
Keyword(s):  
Action Potential ◽  
Synaptic Transmission ◽  
Frequency Response ◽  
Action Potentials ◽  
Nucleus Tractus Solitarius ◽  
Reversal Potential ◽  
Constant Frequency ◽  
Epsp Amplitude ◽  
Postsynaptic Potentials ◽  
Medial Nucleus

1. Synaptic responses of medial nucleus tractus solitarius (mNTS) neurons to solitary tract (ST) activation were studied in a horizontal brain slice preparation of the rat medulla. Slices included sections of ST sufficiently long that the ST could be electrically activated several millimeters from the recording site of cell bodies in mNTS. 2. Three types of synaptic events were evoked in response to ST stimulation: simple excitatory postsynaptic potentials (EPSPs), simple inhibitory postsynaptic potentials (IPSPs), and complex EPSP-IPSP sequences. Simple EPSPs had substantially shorter latencies than IPSPs (3.39 +/- 0.65 ms, mean +/- SE, n = 42, vs. 5.86 +/- 0.71 ms, n = 6, respectively). 3. EPSP amplitude increased linearly with increasing hyperpolarization, with an extrapolated reversal potential near 0 mV. 4. EPSPs were maximal at < 0.5 Hz of sustained, constant-frequency ST stimulation (n = 14). EPSP amplitude declined to an average of 57.5% of control at 10 Hz after 2 s of sustained stimulation. With 1 min of sustained, 100-Hz stimulation, EPSP amplitude declined to near zero. 5. With stimuli intermittently delivered as 100-ms bursts every 300 ms, generally comparable average EPSPs were evoked during constant and burst patterns of ST stimulation. The amplitude of the initial EPSP in each burst was very well maintained even at intraburst stimulation rates of 100 Hz. 6. At resting membrane potentials, low constant frequencies of ST stimulation (< 5 Hz) reliably elicited action potentials and suppressed spontaneous spiking, but higher frequencies led to spike failures (> 85% at 100 Hz). Between 5 and 10 Hz, this periodic stimulation-suppression cycle clearly entrained action potential activity to the ST stimuli. Similar patterns of current pulses (5 ms) reliably evoked action potentials with each pulse to higher frequencies (50 Hz) without failures, and entrainment was similar to ST stimulation. 7. In a subset of nucleus tractus solitarius (NTS) neurons (3 of 9 studied), bursts of ST stimuli were as much as 50% more effective at transmitting high frequencies (> 10 Hz) of ST stimulation than the equivalent constant frequencies (P < 0.0001). 8. The long-latency simple IPSPs with no preceding EPSPs reversed to become depolarizing at potentials more negative than -62.9 +/- 7.0 mV (n = 5) and were blocked by the non-N-methyl-D-aspartate antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (n = 3). The ST stimulation frequency-response relation of these IPSPs was similar to that for the short-latency EPSP response excited by ST synapses. Thus these IPSPs appear to be activated polysynaptically via a glutamatergic-GABAergic sequence in response to ST activation. 9. The results suggest that sensory afferent synapses in mNTS have limited transmission of high-frequency inputs. Both synaptic transmission and the characteristics of the postsynaptic neuron importantly contribute to the action potential transmission from afferent to NTS neuron and beyond. This overall frequency response limitation may contribute to the accommodation of reflex responses from sensory afferent inputs such as arterial baroreceptors within their physiological discharge frequency range.

scholarly journals Direct Actions of Carbenoxolone on Synaptic Transmission and Neuronal Membrane Properties

2009 ◽  
Vol 102 (2) ◽  
pp. 974-978 ◽  
Author(s):  
Kenneth R. Tovar ◽  
Brady J. Maher ◽  
Gary L. Westbrook
Keyword(s):  
Action Potential ◽  
Synaptic Transmission ◽  
Gap Junctions ◽  
Hippocampal Neurons ◽  
Electrical Coupling ◽  
Network Activity ◽  
Membrane Properties ◽  
Neuronal Membrane ◽  
Postsynaptic Currents ◽  
Gap Junctional

The increased appreciation of electrical coupling between neurons has led to many studies examining the role of gap junctions in synaptic and network activity. Although the gap junctional blocker carbenoxolone (CBX) is effective in reducing electrical coupling, it may have other actions as well. To study the non–gap junctional effects of CBX on synaptic transmission, we recorded from mouse hippocampal neurons cultured on glial micro-islands. This recording configuration allowed us to stimulate and record excitatory postsynaptic currents (EPSCs) or inhibitory postsynaptic currents (IPSCs) in the same neuron or pairs of neurons. CBX irreversibly reduced evoked α-amino-3-hydroxy-5-methyl-4-isoxazole-proprionic acid (AMPA) receptor–mediated EPSCs. Consistent with a presynaptic site of action, CBX had no effect on glutamate-evoked whole cell currents and increased the paired-pulse ratio of AMPA and N-methyl-d-aspartate (NMDA) receptor–mediated EPSCs. CBX also reversibly reduced GABAA receptor–mediated IPSCs, increased the action potential width, and reduced the action potential firing rate. Our results indicate CBX broadly affects several neuronal membrane conductances independent of its effects on gap junctions. Thus effects of carbenoxolone on network activity cannot be interpreted as resulting from specific block of gap junctions.

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