scholarly journals Direct Deviations in Astrocyte Free Ca2+ Concentration Control Multiple Arteriole Tone States

Neuroglia ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 48-56
Author(s):  
Jordan N. Haidey ◽  
Grant R. Gordon
Keyword(s):  
Oxygen Tension ◽  
Brain Slices ◽  
Metabolic Status ◽  
Vascular Response ◽  
Direct Manipulation ◽  
Metabolic State ◽  
Whole Cell ◽  
Moderate Elevation ◽  
Cox 1

Astrocytes elicit bidirectional control of microvascular diameter in acutely isolated brain slices through vasoconstriction and vasodilation pathways that can be differentially recruited via the free Ca2+ concentration in endfeet and/or the metabolic status of the tissue. However, the Ca2+-level hypothesis has not been tested using direct manipulation. To overcome this, we used Ca2+-clamp whole-cell patching of peri-arteriole astrocytes to change astrocyte-free Ca2+ to different concentrations and examined the vascular response. We discovered that clamping Ca2+ at the approximate resting value (100 nM) had no impact on arteriole diameter in a pre-constricted arteriole. However, a moderate elevation to 250 nM elicited sustained vasodilation that was blocked by the COX-1 antagonist SC-560 (500 nM). The vasodilation to 250 nM Ca2+ was sensitive to the metabolic state, as it converted to vasoconstriction when oxygen tension was dramatically elevated. In normal oxygen, clamping astrocyte Ca2+ well above the resting level (750 nM) produced sustained vasoconstriction, which converted to vasodilation in the 20-HETE blocker HET0016 (1 μM). This response was fully blocked by the addition of SC-560 (500 nM), showing that 20-HETE-induced vasoconstriction dominated the dilatory action of COX-1. These data demonstrate that direct changes in astrocyte free Ca2+ can control multiple arteriole tone states through different mediators.

scholarly journals Knockouts reveal overlapping functions of M2 and M4 muscarinic receptors and evidence for a local glutamatergic circuit within the laterodorsal tegmental nucleus

2012 ◽  
Vol 108 (10) ◽  
pp. 2751-2766 ◽  
Author(s):  
Kristi A. Kohlmeier ◽  
Masaru Ishibashi ◽  
Jürgen Wess ◽  
Martha E. Bickford ◽  
Christopher S. Leonard
Keyword(s):  
Acetylcholine Receptors ◽  
Brain Slices ◽  
Cholinergic Neurons ◽  
Muscarinic Acetylcholine Receptors ◽  
Feedback Signal ◽  
Laterodorsal Tegmental Nucleus ◽  
Membrane Hyperpolarization ◽  
Whole Cell ◽  
Whole Cell Recording ◽  
Cell Recording

Cholinergic neurons in the laterodorsal tegmental (LDT) and peduncolopontine tegmental (PPT) nuclei regulate reward, arousal, and sensory gating via major projections to midbrain dopamine regions, the thalamus, and pontine targets. Muscarinic acetylcholine receptors (mAChRs) on LDT neurons produce a membrane hyperpolarization and inhibit spike-evoked Ca2+ transients. Pharmacological studies suggest M2 mAChRs are involved, but the role of these and other localized mAChRs (M1--M4) has not been definitively tested. To identify the underlying receptors and to circumvent the limited receptor selectivity of available mAChR ligands, we used light- and electron-immunomicroscopy and whole cell recording with Ca2+ imaging in brain slices from knockout mice constitutively lacking either M2, M4, or both mAChRs. Immunomicroscopy findings support a role for M2 mAChRs, since cholinergic and noncholinergic LDT and pedunculopontine tegmental neurons contain M2-specific immunoreactivity. However, whole cell recording revealed that the presence of either M2 or M4 mAChRs was sufficient, and that the presence of at least one of these receptors was required for these carbachol actions. Moreover, in the absence of M2 and M4 mAChRs, carbachol elicited both direct excitation and barrages of spontaneous excitatory postsynaptic potentials (sEPSPs) in cholinergic LDT neurons mediated by M1 and/or M3 mAChRs. Focal carbachol application to surgically reduced slices suggest that local glutamatergic neurons are a source of these sEPSPs. Finally, neither direct nor indirect excitation were knockout artifacts, since each was detected in wild-type slices, although sEPSP barrages were delayed, suggesting M2 and M4 receptors normally delay excitation of glutamatergic inputs. Collectively, our findings indicate that multiple mAChRs coordinate cholinergic outflow from the LDT in an unexpectedly complex manner. An intriguing possibility is that a local circuit transforms LDT muscarinic inputs from a negative feedback signal for transient inputs into positive feedback for persistent inputs to facilitate different firing patterns across behavioral states.

Electrophysiological Properties of Cholinergic and Noncholinergic Neurons in the Ventral Pallidal Region of the Nucleus Basalis in Rat Brain Slices

2000 ◽  
Vol 83 (5) ◽  
pp. 2649-2660 ◽  
Author(s):  
C. Peter Bengtson ◽  
Peregrine B. Osborne
Keyword(s):  
Brain Slices ◽  
Physiological Role ◽  
Cholinergic Neurons ◽  
Firing Frequency ◽  
Nucleus Basalis ◽  
Morphological Properties ◽  
Inward Rectification ◽  
Resting Membrane Potential ◽  
Whole Cell ◽  
Electrophysiological Properties

The ventral pallidum is a major source of output for ventral corticobasal ganglia circuits that function in translating motivationally relevant stimuli into adaptive behavioral responses. In this study, whole cell patch-clamp recordings were made from ventral pallidal neurons in brain slices from 6- to 18-day-old rats. Intracellular filling with biocytin was used to correlate the electrophysiological and morphological properties of cholinergic and noncholinergic neurons identified by choline acetyltransferase immunohistochemistry. Most cholinergic neurons had a large whole cell conductance and exhibited marked fast (i.e., anomalous) inward rectification. These cells typically did not fire spontaneously, had a hyperpolarized resting membrane potential, and also exhibited a prominent spike afterhyperpolarization (AHP) and strong spike accommodation. Noncholinergic neurons had a smaller whole cell conductance, and the majority of these cells exhibited marked time-dependent inward rectification that was due to an h-current. This current activated slowly over several hundred milliseconds at potentials more negative than −80 mV. Noncholinergic neurons fired tonically in regular or intermittent patterns, and two-thirds of the cells fired spontaneously. Depolarizing current injection in current clamp did not cause spike accommodation but markedly increased the firing frequency and in some cells also altered the pattern of firing. Spontaneous tetrodotoxin-sensitive GABAA-mediated inhibitory postsynaptic currents (IPSCs) were frequently recorded in noncholinergic neurons. These results show that cholinergic pallidal neurons have similar properties to magnocellular cholinergic neurons in other parts of the forebrain, except that they exhibit strong spike accommodation. Noncholinergic ventral pallidal neurons have large h-currents that could have a physiological role in determining the rate or pattern of firing of these cells.

Acute reduction in whole cell conductance in anoxic turtle brain

1999 ◽  
Vol 277 (3) ◽  
pp. R887-R893 ◽  
Author(s):  
H. S. Ghai ◽  
L. T. Buck
Keyword(s):  
Brain Slices ◽  
Cell Voltage ◽  
Dependent Manner ◽  
Recording Electrode ◽  
Whole Cell ◽  
Artificial Cerebrospinal Fluid ◽  
Intracellular Ca ◽  
Specific Antagonist ◽  
Acute Changes ◽  
Dose Dependent

We tested the effect of anoxia, a “mimic” turtle artificial cerebrospinal fluid (aCSF) consisting of high Ca2+ and Mg2+ concentrations and low pH and adenosine perfusions, on whole cell conductance ( G w) in turtle brain slices using a whole cell voltage-clamp technique. With EGTA in the recording electrode, anoxic or adenosine perfusions did not change G w significantly (values range between 2.15 ± 0.24 and 3.24 ± 0.56 nS). However, perfusion with normoxic or anoxic mimic aCSF significantly decreased G w. High [Ca2+] (4.0 or 7.8 mM) perfusions alone could reproduce the changes in G w found with the mimic perfusions. With the removal of EGTA from the recording electrode, G wdecreased significantly during both anoxic and adenosine perfusions. The A1-receptor agonist N 6-cyclopentyladenosine reduced G w in a dose-dependent manner, whereas the A1-receptor specific antagonist 8-cyclopentyl-1,3-dipropylxanthine blocked both the adenosine- and anoxic-mediated changes in G w. These data suggest a mechanism involving A1-receptor-mediated changes in intracellular [Ca2+] that result in acute changes in G w with the onset of anoxia.

scholarly journals Whole-cell Currents Induced by Puff Application of GABA in Brain Slices

10.3791/56387 ◽  
2017 ◽  
Author(s):  
Yangjian Feng ◽  
Binliang Tang ◽  
Ming Chen ◽  
Li Yang
Keyword(s):  
Brain Slices ◽  
Whole Cell

scholarly journals Anticonvulsant effect of dipropofol by enhancing native GABA currents in cortical neurons in mice

2018 ◽  
Vol 120 (3) ◽  
pp. 1404-1414 ◽  
Author(s):  
Jingliang Zhang ◽  
Xiaoling Chen ◽  
Matti Kårbø ◽  
Yi Zhao ◽  
Long An ◽  
...  
Keyword(s):  
Patch Clamp ◽  
Mouse Model ◽  
Kainic Acid ◽  
Neuronal Excitability ◽  
Brain Slices ◽  
Anticonvulsant Effect ◽  
Dependent Manner ◽  
Whole Cell ◽  
Whole Cell Patch Clamp ◽  
Dose Dependent

Temporal lobe epilepsy (TLE), the most common pharmacoresistant focal epilepsy disorder, remains a major unmet medical need. Propofol is used as a short-acting medication for general anesthesia and refractory status epilepticus with issues of decreased consciousness and memory loss. Dipropofol, a derivative of propofol, has been reported to exert antioxidative and antibacterial activities. Here we report that dipropofol exerted anticonvulsant activity in a mouse model of kainic acid-induced seizures. Whole cell patch-clamp recordings of brain slices from the medial entorhinal cortex (mEC) revealed that dipropofol hyperpolarized the resting membrane potential and reduced the number of action potential firings, resulting in suppression of cortical neuronal excitability. Furthermore, dipropofol activated native tonic GABAA currents of mEC layer II stellate neurons in a dose-dependent manner with an EC50 value of 9.3 ± 1.6 μM (mean ± SE). Taken together, our findings show that dipropofol activated GABAA currents and exerted anticonvulsant activities in mice, thus possessing developmental potential for new anticonvulsant therapy. NEW & NOTEWORTHY The anticonvulsant effect of dipropofol was shown in a mouse model of kainic acid-induced seizures. Whole cell patch-clamp recordings of brain slices showed suppression of cortical neuronal excitability by dipropofol. Dipropofol activated the native tonic GABAA currents in a dose-dependent manner.

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