Impaired working memory is a common feature of neuropsychiatric disorders. It is dependent on control of the medial prefrontal cortex (mPFC) neurons by dopamine. The purpose of this study was to test ...the effects of a D1/5-type dopamine receptor agonist (SKF 38393, 10 microM) on the membrane potential and on voltage-dependent fast-inactivating Na+ currents in mPFC pyramidal neurons obtained from adult (9-week-old) rats. Treatment of the pyramidal neurons with SKF 38393 did not affect the membrane potential recorded with the perforated-patch method. When recordings were performed in cellattached configuration, the application of SKF 38393 did not change the Na+ current amplitude and shifted the currentvoltage relationship of the Na+ currents towards hyperpolarisation, thus resulting in an increase of the current amplitudes in response to suprathreshold depolarisations. Pretreatment of the cells with a D1/5 receptor antagonist (SCH 23390, 10 microM) abolished the effect of the D1/5-type receptors on Na+ currents. The effect of the D1/5 agonist was replicated by treating the cells with a membrane-permeable analogue, cAMP (8-bromo-cAMP, 100 microM), and the effect was blocked by treating the cells with a protein kinase A inhibitor, (H-89, 2 microM). In recordings performed from mechanically and enzymatically dispersed pyramidal neurons in the whole-cell configuration, when the cell interior was dialysed with pipette solution, application of the D1/5 agonist decreased the Na+ current amplitude without changing the current-voltage relationship. We conclude that in the mPFC pyramidal neurons in slices with an intact intracellular environment (recordings in the cell-attached configuration), the activation of D1/5 dopamine receptors increases the fast-inactivating Na+ current availability in response to suprathreshold depolarisations. The maximum Na+ current amplitude was not changed. A cAMP/protein kinase A pathway was responsible for the signal transduction from the D1/5 dopamine receptors to the Na+ channels.
The gramicidin-perforated patch-clamp technique is indispensable for recording neuronal activities without changing the intracellular Cl
concentration. Conventionally, gramicidin contained in the ...pipette fluid is delivered to the cell membrane by passive diffusion. Gramicidin deposited on the pipette orifice sometimes hampers giga-seal formation, and perforation progresses only slowly. These problems may be circumvented by delivering a high concentration of gramicidin from an intra-pipette capillary after a giga-seal is formed. We herein describe the detailed protocol of this improved method. This protocol would greatly facilitate the investigation of Cl
gradient-dependent neuronal activities.
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•PDS arise in the course of experimentally-provoked seizure-like activity.•PDS can also be induced by cellular processes typical of seizure aftermath.•PDS closely resemble modulatory ...electrical activity patterns in neurodevelopment.•L-type calcium channels are essential for formation of these PDS.•L-type calcium channels potentially a valuable target to interfere with PDS effects.
Since their discovery in the 1960s, the term paroxysmal depolarization shift (PDS) has been applied to a wide variety of reinforced neuronal discharge patterns. Occurrence of PDS as cellular correlates of electrographic spikes during latent phases of insult-induced rodent epilepsy models and their resemblance to giant depolarizing potentials (GDPs) nourished the idea that PDS may be involved in epileptogenesis. Both GDPs and – in analogy – PDS may lead to progressive changes of neuronal properties by generation of pulsatile intracellular Ca2+ elevations. Herein, a key element is the gating of L-type voltage gated Ca2+ channels (LTCCs, Cav1.x family), which may convey Ca2+ signals to the nucleus. Accordingly, the present study investigates various insult-associated neuronal challenges for their propensities to trigger PDS in a LTCC-dependent manner. Our data demonstrate that diverse disturbances of neuronal function are variably suited to induce PDS-like events, and the contribution of LTCCs is essential to evoke PDS in rat hippocampal neurons that closely resemble GDPs. These PDS appear to be initiated in the dendritic sub-compartment. Their morphology critically depends on the position of recording electrodes and on their rate of occurrence. These results provide novel insight into induction mechanisms, origin, variability, and co-existence of PDS with other discharge patterns and thereby pave the way for future investigations regarding the role of PDS in epileptogenesis.
Using single neurons of rat paratracheal ganglia (PTG) attached with presynaptic boutons, the effects of suplatast tosilate on excitatory postsynaptic currents (EPSCs) were investigated with ...nystatin-perforated patch-clamp recording technique. We found that suplatast concentration dependently inhibited the EPSC amplitude and its frequency in single PTG neurons attached with presynaptic boutons. EPSC frequency was higher sensitive to suplatast than EPSC amplitude. IC
for EPSC frequency was 1.1 × 10
M, being similar to that for the effect on histamine release from mast cells and lower than that for the inhibitory effect on cytokine production. Suplatast also inhibited the EPSCs potentiated by bradykinin (BK), but it did not affect the potentiation itself by BK. Thus suplatast inhibited the EPSC of PTG neurons attached with presynaptic boutons at both the presynaptic and postsynaptic sites.
In this study, using single neurons of rat paratracheal ganglia (PTG) attached with presynaptic boutons, the effects of suplatast tosilate on excitatory postsynaptic currents (EPSCs) were investigated with patch-clamp recording technique. We found that suplatast concentration dependently inhibited the EPSC amplitude and its frequency in single PTG neurons attached with presynaptic boutons. Thus suplatast inhibited the function of PTG neurons at both of presynaptic and postsynaptic sites.
Light-driven modulation of neuronal activity at high spatial-temporal resolution is becoming of high interest in neuroscience. In addition to optogenetics, nongenetic membrane-targeted nanomachines ...that alter the electrical state of the neuronal membranes are in demand. Here, we engineered and characterized a photoswitchable conjugated compound (BV-1) that spontaneously partitions into the neuronal membrane and undergoes a charge transfer upon light stimulation. The activity of primary neurons is not affected in the dark, whereas millisecond light pulses of cyan light induce a progressive decrease in membrane resistance and an increase in inward current matched to a progressive depolarization and action potential firing. We found that illumination of BV-1 induces oxidation of membrane phospholipids, which is necessary for the electrophysiological effects and is associated with decreased membrane tension and increased membrane fluidity. Time-resolved atomic force microscopy and molecular dynamics simulations performed on planar lipid bilayers revealed that the underlying mechanism is a light-driven formation of pore-like structures across the plasma membrane. Such a phenomenon decreases membrane resistance and increases permeability to monovalent cations, namely, Na+, mimicking the effects of antifungal polyenes. The same effect on membrane resistance was also observed in nonexcitable cells. When sustained light stimulations are applied, neuronal swelling and death occur. The light-controlled pore-forming properties of BV-1 allow performing “on-demand” light-induced membrane poration to rapidly shift from cell-attached to perforated whole-cell patch-clamp configuration. Administration of BV-1 to ex vivo retinal explants or in vivo primary visual cortex elicited neuronal firing in response to short trains of light stimuli, followed by activity silencing upon prolonged light stimulations. BV-1 represents a versatile molecular nanomachine whose properties can be exploited to induce either photostimulation or space-specific cell death, depending on the pattern and duration of light stimulation.
Understanding dendritic excitability is essential for a complete and precise characterization of neurons' input-output relationships. Theoretical and experimental work demonstrates that the ...electrotonic and nonlinear properties of dendrites can alter the amplitude (e.g., through amplification) and latency of synaptic inputs as viewed in the axosomatic region where spike timing is determined. The gold-standard technique to study dendritic excitability is using dual-patch recordings with a high-resistance electrode used to patch a piece of distal dendrite in addition to a somatic patch electrode. However, this approach is often impractical when distal dendrites are too fine to patch. Therefore, we developed a technique that utilizes the expression of Channelrhodopsin-2 (ChR2) to study dendritic excitability in acute brain slices through the combination of a somatic patch electrode and optogenetic activation. The protocol describes how to prepare acute slices from mice that express ChR2 in specific cell types, and how to use two modes of light stimulation: proximal (which activates the soma and proximal dendrites in a ~100 µm diameter surrounding the soma) with the use of a high-magnification objective and full-field stimulation through a low-magnification objective (which activates the entire somato-dendritic field of the neuron). We use this technique in conjunction with various stimulation protocols to estimate model-based spectral components of dendritic filtering and the impact of dendrites on phase response curves, peri-stimulus time histograms, and entrainment of pacemaking neurons. This technique provides a novel use of optogenetics to study intrinsic dendritic excitability through the use of standard patch-clamp slice physiology. Key features • A method for studying the effects of electrotonic and nonlinear dendritic properties on the sub- and suprathreshold responses of pacemaking neurons. • Combines somatic patch clamp or perforated patch recordings with optogenetic activation in acute brain slices to investigate dendritic linear transformation without patching the dendrite. • Oscillatory illumination at various frequencies estimates spectral properties of the dendrite using subthreshold voltage-clamp recordings and studies entrainment of pacemakers in current clamp recordings. • This protocol uses Poisson white noise illumination to estimate dendritic phase response curves and peri-stimulus time histograms.
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•Combining added buffer approach and perforated patch clamp optimizes quantification of Ca2+ handling.•β-escin as perforating agent allows controlled Ca2+ buffer loading while ...preserving cytoplasmic pathways.•Mobile and Immobile Ca2+ buffers can be quantified.
Ca2+ functions as an important intracellular signal for a wide range of cellular processes. These processes are selectively activated by controlled spatiotemporal dynamics of the free cytosolic Ca2+. Intracellular Ca2+ dynamics are regulated by numerous cellular parameters. Here, we established a new way to determine neuronal Ca2+ handling properties by combining the ‘added buffer’ approach 1 with perforated patch-clamp recordings 2. Since the added buffer approach typically employs the standard whole-cell configuration for concentration-controlled Ca2+ indicator loading, it only allows for the reliable estimation of the immobile fraction of intracellular Ca2+ buffers. Furthermore, crucial components of intracellular signaling pathways are being washed out during prolonged whole-cell recordings, leading to cellular deterioration. By combining the added buffer approach with perforated patch-clamp recordings, these issues are circumvented, allowing the precise quantification of the cellular Ca2+ handling properties, including immobile as well as mobile Ca2+ buffers.
The receptor potentials of taste receptor cells remain unclear. Here, we demonstrate that taste receptor cells generate oscillating depolarization (
= 7) with action potentials in response to sweet, ...bitter, umami, and salty taste substances. At a lower concentration of taste substances, taste receptor cells exhibited oscillations in membrane potentials with a low frequency and small magnitude of depolarization. Although the respective waves contained no or 1-2 action potentials, the taste receptor cells generated action potentials continuously in the presence of taste stimuli. Both the frequency and magnitude of oscillations increased when the concentration was increased, to 0.67-1.43 Hz (
= 3) and Δ39-53 mV (
= 3) in magnitude from -64.7 ± 4.2 to -18.7 ± 5.9 mV, which may activate the ATP-permeable ion channels. In contrast, a sour tastant (10-mM HCl) induced membrane depolarization (Δ19.4 ± 9.5 mV,
= 4) with action potentials in type III taste receptor cells. Interestingly, NaCl (1 M) taste stimuli induced oscillation (
= 2) or depolarization (Δ10.5 ± 5.7 mV at the tonic component,
= 9). Our results indicate that the frequency and magnitude of oscillations increased with increasing taste substance concentrations. These parameters may contribute to the expression of taste "thickness."
Early life stress (ELS) alters the excitation-inhibition-balance (EI-balance) in various rodent brain areas and may be responsible for behavioral impairment later in life. The EI-balance is (amongst ...others) influenced by the switch of GABAergic transmission from excitatory to inhibitory, the so-called “GABA-switch”.
Here, we investigated how ELS affects the GABA-switch in mouse infralimbic Prefrontal Cortex layer 2/3 neurons, using the limited-nesting-and-bedding model. In ELS mice, the GABA-switch occurred already between postnatal day (P) 6 and P9, as opposed to P15–P21 in controls. This was associated with increased expression of the inward chloride transporter NKCC1, compared to the outward chloride transporter KCC2, both of which are important for the intracellular chloride concentration and, hence, the GABA reversal potential (Erev). Chloride transporters are not only important for regulating chloride concentration postsynaptically, but also presynaptically. Depending on the Erev of GABA, presynaptic GABAA receptor stimulation causes a depolarization or hyperpolarization, and thereby enhanced or reduced fusion of glutamate vesicles respectively, in turn changing the frequency of miniature postsynaptic currents (mEPSCs). In accordance, bumetanide, a blocker of NKCC1, shifted the Erev GABA towards more hyperpolarized levels in P9 control mice and reduced the mEPSC frequency. Other modulators of chloride transporters, e.g. VU0463271 (a KCC2 antagonist) and aldosterone -which increases NKCC1 expression-did not affect postsynaptic Erev in ELS P9 mice, but did increase the mEPSC frequency. We conclude that the mouse GABA-switch is accelerated after ELS, affecting both the pre- and postsynaptic chloride homeostasis, the former altering glutamatergic transmission. This may considerably affect brain development.
•Early life stress (limited bedding and nesting model) accelerates the GABA-switch in IL-PFC neurons of male mice.•NKCC1 expression is decreased directly after early life stress.•Presynaptic Cl− concentration in the IL-PFC most likely determines the GABAA receptor mediated release of glutamate.•Overall, early life stress causes an attenuation of the excitatory tone in the mouse infralimbic prefrontal cortex.
In the adult brain, chloride (Cl
−
) influx through GABA
A
receptors is an important mechanism of synaptic inhibition. However, under a variety of circumstances, including acquired epilepsy, ...neuropathic pain, after trains of action potentials or trauma, and during normal early brain development, GABA
A
receptor activation excites neurons by gating Cl
−
efflux because the intracellular Cl
−
concentration (Cl
i
) is elevated. These findings require an inducible, active mechanism of chloride accumulation. We used gramicidin-perforated patch recordings to characterize Cl
−
transport via NKCC1, the principal neuronal Cl
−
accumulator, in neonatal CA1 pyramidal neurons. NKCC1 activity was required to maintain elevated Cl
i
such that GABA
A
receptor activation was depolarizing. Kinetic analysis of NKCC1 revealed reversible transmembrane Cl
−
transport characterized by a large maximum velocity (
v
max
) and high affinity (
K
m
), so that NKCC1 transport was limited only by the net electrochemical driving force for Na
+
, K
+
, and Cl
−
. At the steady-state Cl
i
, NKCC1 was at thermodynamic equilibrium, and there was no evidence of net Cl
−
transport. Trains of action potentials that have been previously shown to induce persistent changes in neuronal
E
Cl
(reversal potential for Cl
−
) did not alter
v
max
or
K
m
of NKCC1. Rather, action potentials shifted the thermodynamic set point, the steady-state Cl
i
at which there was no net NKCC1-mediated Cl
−
transport. The persistent increase in Cl
i
required intact α2/α3 Na
+
-K
+
-ATPase activity, indicating that trains of action potentials reset the thermodynamic equilibrium for NKCC1 transport by lowering Na
i
. Activity-induced changes in Na
+
-K
+
-ATPase activity comprise a novel mechanism for persistent alterations in synaptic signaling mediated by GABA.
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