Electrical Synapses Between AII Amacrine Cells: Dynamic Range and Functional Consequences of Variation in Junctional Conductance

2008 ◽  
Vol 100 (6) ◽  
pp. 3305-3322 ◽  
Author(s):  
Margaret Lin Veruki ◽  
Leif Oltedal ◽  
Espen Hartveit
Keyword(s):  
Dynamic Range ◽  
Amacrine Cells ◽  
Electrical Synapses ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Junctional Conductance ◽  
Coupled Cells ◽  
Functional Consequences ◽  
Aii Amacrine Cells ◽  
Aii Amacrine

AII amacrine cells form a network of electrically coupled interneurons in the mammalian retina and tracer coupling studies suggest that the junctional conductance ( Gj) can be modulated. However, the dynamic range of Gj and the functional consequences of varying Gj over the dynamic range are unknown. Here we use whole cell recordings from pairs of coupled AII amacrine cells in rat retinal slices to provide direct evidence for physiological modulation of Gj, appearing as a time-dependent increase from about 500 pS to a maximum of about 3,000 pS after 30–90 min of recording. The increase occurred in recordings with low- but not high-resistance pipettes, suggesting that it was related to intracellular washout and perturbation of a modulatory system. Computer simulations of a network of electrically coupled cells verified that our recordings were able to detect and quantify changes in Gj over a large range. Dynamic-clamp electrophysiology, with insertion of electrical synapses between AII amacrine cells, allowed us to finely and reversibly control Gj within the same range observed for physiologically coupled cells and to examine the quantitative relationship between Gj and steady-state coupling coefficient, synchronization of subthreshold membrane potential fluctuations, synchronization and transmission of action potentials, and low-pass filter characteristics. The range of Gj values over which signal transmission was modulated depended strongly on the specific functional parameter examined, with the largest range observed for action potential transmission and synchronization, suggesting that the full range of Gj values observed during spontaneous run-up of coupling could represent a physiologically relevant dynamic range.

Meclofenamic Acid Blocks Electrical Synapses of Retinal AII Amacrine and on-Cone Bipolar Cells

2009 ◽  
Vol 101 (5) ◽  
pp. 2339-2347 ◽  
Author(s):  
Margaret Lin Veruki ◽  
Espen Hartveit
Keyword(s):  
Amacrine Cells ◽  
Bipolar Cells ◽  
Electrical Synapse ◽  
Dependent Manner ◽  
Electrical Synapses ◽  
Meclofenamic Acid ◽  
Aii Amacrine Cells ◽  
Rod Pathway ◽  
Aii Amacrine ◽  
Cone Bipolar Cells

Gap junction channels constitute specialized intercellular contacts that can serve as electrical synapses. In the rod pathway of the retina, electrical synapses between AII amacrine cells express connexin 36 (Cx36) and electrical synapses between AII amacrines and on-cone bipolar cells express Cx36 on the amacrine side and Cx36 or Cx45 on the bipolar side. For physiological investigations of the properties and functions of these electrical synapses, it is highly desirable to have access to potent pharmacological blockers with selective and reversible action. Here we use dual whole cell voltage-clamp recordings of pairs of AII amacrine cells and pairs of AII amacrine and on-cone bipolar cells in rat retinal slices to directly measure the junctional conductance ( Gj) between electrically coupled cells and to study the effect of the drug meclofenamic acid (MFA) on Gj. Consistent with previous tracer coupling studies, we found that MFA reversibly blocked the electrical synapse currents in a concentration-dependent manner, with complete block at 100 μM. Whereas MFA evoked a detectable decrease in Gj within minutes of application, the time to complete block of Gj was considerably longer, typically 20–40 min. After washout, Gj recovered to 20–90% of the control level, but the time to maximum recovery was typically >1 h. These results suggest that MFA can be a useful drug to investigate the physiological functions of electrical synapses in the rod pathway, but that the slow kinetics of block and reversal might compromise interpretation of the results and that explicit monitoring of Gj is desirable.

Electrical Coupling and Passive Membrane Properties of AII Amacrine Cells

2010 ◽  
Vol 103 (3) ◽  
pp. 1456-1466 ◽  
Author(s):  
Margaret Lin Veruki ◽  
Leif Oltedal ◽  
Espen Hartveit
Keyword(s):  
Amacrine Cell ◽  
Electrical Coupling ◽  
Amacrine Cells ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Membrane Properties ◽  
Total Input ◽  
Junctional Conductance ◽  
Aii Amacrine Cells ◽  
Aii Amacrine

AII amacrine cells in the mammalian retina are connected via electrical synapses to on-cone bipolar cells and to other AII amacrine cells. To understand synaptic integration in these interneurons, we need information about the junctional conductance ( gj), the membrane resistance ( rm), the membrane capacitance ( Cm), and the cytoplasmic resistivity ( Ri). Due to the extensive electrical coupling, it is difficult to obtain estimates of rm, as well as the relative contribution of the junctional and nonjunctional conductances to the total input resistance of an AII amacrine cell. Here we used dual voltage-clamp recording of pairs of electrically coupled AII amacrine cells in an in vitro slice preparation from rat retina and applied meclofenamic acid (MFA) to block the electrical coupling and isolate single AII amacrines electrically. In the control condition, the input resistance ( Rin) was ∼620 MΩ and the apparent rm was ∼760 MΩ. After block of electrical coupling, determined by estimating gj in the dual recordings, Rin and rm were ∼4,400 MΩ, suggesting that the nongap junctional conductance of an AII amacrine cell is ∼16% of the total input conductance. Control experiments with nucleated patches from AII amacrine cells suggested that MFA had no effect on the nongap junctional membrane of these cells. From morphological reconstructions of AII amacrine cells filled with biocytin, we obtained a surface area of ∼900 μm2 which, with a standard value for Cm of 0.01 pF/μm2, corresponds to an average capacitance of ∼9 pF and a specific membrane resistance of ∼41 kΩ cm2. Together with information concerning synaptic connectivity, these data will be important for developing realistic compartmental models of the network of AII amacrine cells.

scholarly journals Wideband Reconfigurable Integrated Low-Pass Filter for 5G Compatible Software Defined Radio Solutions

Electronics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 734
Author(s):  
Karolis Kiela ◽  
Marijan Jurgo ◽  
Vytautas Macaitis ◽  
Romualdas Navickas
Keyword(s):  
Software Defined Radio ◽  
Dynamic Range ◽  
Noise Figure ◽  
Harmonic Distortion ◽  
Cmos Process ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Filter Performance ◽  
Low Pass ◽  
Bandwidth Tuning

This article presents a wideband reconfigurable integrated low-pass filter (LPF) for 5G NR compatible software-defined radio (SDR) solutions. The filter uses Active-RC topology to achieve high linearity performance. Its bandwidth can be tuned from 2.5 MHz to 200 MHz, which corresponds to a tuning ratio of 92.8. The order of the filter can be changed between the 2nd, 4th, or 6th order; it has built-in process, voltage, and temperature (PVT) compensation with a tuning range of ±42%; and power management features for optimization of the filter performance across its entire range of bandwidth tuning. Across its entire order, bandwidth, and power configuration range, the filter achieves in-band input-referred third-order intercept point (IIP3) between 32.7 dBm and 45.8 dBm, spurious free dynamic range (SFDR) between 63.6 dB and 79.5 dB, 1 dB compression point (P1dB) between 9.9 dBm and 14.1 dBm, total harmonic distortion (THD) between −85.6 dB and −64.5 dB, noise figure (NF) between 25.9 dB and 31.8 dB and power dissipation between 1.19 mW and 73.4 mW. The LPF was designed and verified using 65 nm CMOS process; it occupies a 0.429 mm2 area of silicon and uses a 1.2 V supply.

scholarly journals AII amacrine cells discriminate between heterocellular and homocellular locations when assembling connexin36-containing gap junctions

2014 ◽  
Vol 127 (6) ◽  
pp. 1190-1202 ◽  
Author(s):  
A. Meyer ◽  
G. Hilgen ◽  
B. Dorgau ◽  
E. M. Sammler ◽  
R. Weiler ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Amacrine Cells ◽  
Aii Amacrine Cells ◽  
Aii Amacrine

scholarly journals Ladder-Based Synthesis and Design of Low-Frequency Buffer-Based CMOS Filters

Electronics ◽  
2021 ◽  
Vol 10 (23) ◽  
pp. 2931
Author(s):  
Waldemar Jendernalik ◽  
Jacek Jakusz ◽  
Grzegorz Blakiewicz
Keyword(s):  
Dynamic Range ◽  
Low Voltage ◽  
Supply Voltage ◽  
Low Frequency ◽  
Cmos Technology ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Biomedical Sensors ◽  
Filter Synthesis ◽  
Cascade Method

Buffer-based CMOS filters are maximally simplified circuits containing as few transistors as possible. Their applications, among others, include nano to micro watt biomedical sensors that process physiological signals of frequencies from 0.01 Hz to about 3 kHz. The order of a buffer-based filter is not greater than two. Hence, to obtain higher-order filters, a cascade of second-order filters is constructed. In this paper, a more general method for buffer-based filter synthesis is developed and presented. The method uses RLC ladder prototypes to obtain filters of arbitrary orders. In addition, a set of novel circuit solutions with ultra-low voltage and power are proposed. The introduced circuits were synthesized and simulated using 180-nm CMOS technology of X-FAB. One of the designed circuits is a fourth-order, low-pass filter that features: 100-Hz passband, 0.4-V supply voltage, power consumption of less than 5 nW, and dynamic range above 60 dB. Moreover, the total capacitance of the proposed filter (31 pF) is 25% lower compared to the structure synthesized using a conventional cascade method (40 pF).

scholarly journals Spikelets and bursts in axonless retinal AII amacrine cells coupled by gap junctions

2013 ◽  
Vol 14 (S1) ◽  
Author(s):  
Hermann Riecke ◽  
Hannah Choi ◽  
Mark S Cembrowski ◽  
William L Kath ◽  
Joshua H Singer
Keyword(s):  
Gap Junctions ◽  
Amacrine Cells ◽  
Aii Amacrine Cells ◽  
Aii Amacrine

scholarly journals Synaptic Transfer between Rod and Cone Pathways Mediated by AII Amacrine Cells in the Mouse Retina

2018 ◽  
Vol 28 (17) ◽  
pp. 2739-2751.e3 ◽  
Author(s):  
Cole W. Graydon ◽  
Evan E. Lieberman ◽  
Nao Rho ◽  
Kevin L. Briggman ◽  
Joshua H. Singer ◽  
...  
Keyword(s):  
Amacrine Cells ◽  
Mouse Retina ◽  
Aii Amacrine Cells ◽  
Aii Amacrine

Encoder response of isolated frog muscle spindle elicited by pseudorandom noise stimuli

1986 ◽  
Vol 55 (1) ◽  
pp. 13-22 ◽  
Author(s):  
H. Querfurth
Keyword(s):  
Muscle Spindle ◽  
Action Potentials ◽  
Dynamic Range ◽  
Frog Muscle ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Pseudorandom Noise ◽  
Afferent Discharge ◽  
The Mean ◽  
Discharge Patterns

The present experiments investigated the signal transfer in the isolated frog muscle spindle by using pseudorandom noise (PRN) as the analytical probe. In order to guarantee that the random stimulus covered the entire dynamic range of the receptor, PRN stimuli of different intensities were applied around a constant mean length, or PRN stimuli of the same intensity were used while varying the mean length of the spindle. Subthreshold receptor potentials, local responses, and propagated action potentials were recorded simultaneously from the first Ranvier node of the afferent stem fiber, thus providing detailed insight into the spike-initiating process within a sensory receptor. Relevant features of the PRN stimulus were evaluated by a preresponse averaging technique. Up to tau = 2 ms before each action potential the encoder selected a small set of steeply rising stretch transients. A second component of the preresponse stimulus ensemble (tau = 2-5 ms) opposed the overall stretch bias. Since each steeply rising stretch transient evoked a steeply rising receptor potential that guaranteed the critical slope condition of the encoding site, this stimulus profile was most effective in initiating action potentials. The dynamic range of the muscle spindle receptor extended from resting length, L0, to about L0 + 100 microns. At the lower limit (L0) the encoding membrane was depolarized to its firing level and discharged action potentials spontaneously. When random stretches larger than the upper region of the dynamic range were applied, the spindle discharged at the maximum impulse rate and displayed no depolarization block or "overstretch" phenomenon. Random stretches applied within the dynamic range evoked regular discharge patterns that were firmly coupled to the PRN. The afferent discharge rate increased, and the precision of phase-locking improved when the intensity of the PRN stimulus was increased around a constant mean stretch; or the mean prestretch level was raised to higher values while the intensity of the PRN stimulus was kept constant. In the case when the PRN stimulus covered the entire dynamic range, the temporal pattern of the afferent discharge remained constant for at least 10 consecutive sequences of PRN. A spectral analysis of the discharge patterns averaged over several sequences of PRN was employed. At the same stimulus intensity the response spectra displayed low-pass filter characteristics with a 10-dB bandwidth of 300 Hz and a high-frequency slope of -12 dB/oct. Increasing the mean intensity of the PRN stimulus or raising the prestretch level increased the response power.(ABSTRACT TRUNCATED AT 400 WORDS)

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