5-Hydroxytryptamine Responses in Immature Rat Rostral Ventrolateral Medulla Neurons In Vitro

1998 ◽  
Vol 80 (3) ◽  
pp. 1033-1041 ◽  
Author(s):  
L. L. Hwang ◽  
N. J. Dun
Keyword(s):  
Receptor Antagonist ◽  
Receptor Agonist ◽  
Reversal Potential ◽  
Input Resistance ◽  
Rostral Ventrolateral Medulla ◽  
Ventrolateral Medulla ◽  
Immature Rat ◽  
Apparent Change ◽  
Biphasic Responses

Hwang, L. L. and N. J. Dun. 5-Hydroxytryptamine responses in immature rat rostral ventrolateral medulla neurons in vitro. J. Neurophysiol. 80: 1033–1041, 1998. Whole cell patch recordings were made from rostral ventrolateral medulla (RVLM) neurons of brainstem slices from 8- to 12-day-old rats. By superfusion or pressure ejection to RVLM neurons, 5-hydroxytryptamine (5-HT) elicited three types of membrane potential changes: a slow hyperpolarization (5-HTH), a slow depolarization (5-HTD) and a biphasic response, which persisted in a tetrodotoxin (TTX, 0.3 μM)-containing solution. 5-HTH were accompanied by a decrease of input resistance in the majority of responsive neurons. Hyperpolarization reduced and depolarization increased the 5-HTH; the mean reversal potential was −92.3 mV in 3.1 mM and shifted to −69.3 mV in 7 mM [K+]o. Barium (Ba2+, 0.1 mM) but not tetraethylammonium (TEA, 10 mM) suppressed 5-HTH. The 5-HT1A receptor agonist (±)-8-hydroxy-dipropylamino-tetralin (8-OH-DPAT; 5–50 μM) hyperpolarized RVLM neurons. The 5-HT1A antagonist pindobind-5-HT1A (PBD; 1–3 μM) and the 5-HT2/5-HT1 receptor antagonist spiperone (1–10 μM) suppressed 5-HTH and the hyperpolarizing phase of biphasic responses; the 5-HT2 receptor antagonist ketanserin (3 μM) was without significant effect. 5-HTD were associated with an increase or no apparent change of input resistance in RVLM neurons. Hyperpolarization of the membrane decreased or caused no apparent change in 5-HTD. 5-HTD were reduced in an elevated [K+]o (7.0 mM) solution and >60% in a low Na+ (26 mM) solution and were not significantly changed in a low Cl− (6.7 mM) or Ca2+-free/high Mg2+ (10.9 mM) solution. The 5-HT2 receptor agonist α-methyl-5-HT (50 μM) depolarized RVLM neurons, and the 5-HT2 antagonist ketanserin (1–10 μM) attenuated the 5-HTD and the depolarizing phase of biphasic responses, whereas the 5-HT1A receptor antagonist PBD (2 μM) was without effect. Inclusion of the hydrolysis resistant guanine nucleotide GDP-β-S in patch solution significantly reduced the 5-HTH as well as the 5-HTD. The present study shows that, in the immature rat RVLM neurons, 5-HT causes a slow hyperpolarization and depolarization probably by interacting with 5-HT1A and 5-HT2 receptors, which are G-proteins coupled. 5-HTH may involve an increase of an inwardly rectifying K+ conductance, and 5-HTD appear to be caused by a decrease of K+ conductance and/or increase of nonselective cation conductance.

Effect of cholinergic agonists on bulbospinal C1 neurons in rats

1997 ◽  
Vol 272 (1) ◽  
pp. R249-R258 ◽  
Author(s):  
D. Huangfu ◽  
M. Schreihofer ◽  
P. G. Guyenet
Keyword(s):  
Brain Slices ◽  
Reversal Potential ◽  
Input Resistance ◽  
Neonatal Rat ◽  
Ventrolateral Medulla ◽  
Cholinergic Agonists ◽  
Inward Currents ◽  
Tone Generation

Cholinergic inputs to the rostral ventrolateral medulla (RVLM) may contribute to sympathetic tone generation. The present study analyzes the response of RVLM neurons to cholinergic agonists. In chloralose-anesthetized rats iontophoresis of carbachol excited RVLM sympathoexcitatory neurons (+69% from resting level of 11.9 +/- 2 spikes/s; n = 28). This effect was reduced 85% by iontophoresis of methylatropine and abolished by intravenous scopolamine. Iontophoresis of nicotine or hexamethonium was ineffective. In contrast, most RVLM respiratory units were inhibited by carbachol. Whole cell recordings of bulbospinal RVLM neurons were made in neonatal rat brain slices (54 cells, 24 C1 adrenergic neurons). In current-clamp recordings (without tetrodotoxin) carbachol produced depolarization, increased postsynaptic potential frequency, and decreased input resistance. In voltage-clamp recording (-50 to -60 mV; 1 microM tetrodotoxin) carbachol produced inward current [50% effective concentration (EC50): 10 +/- 1 microM; 12.6 +/- 2 pA at 30 microM; n = 16] that persisted in low Ca2+/high Mg2+ (n = 6). Muscarine (30 microM) caused smaller inward currents (2.6 +/- 0.6 pA; n = 16). The carbachol-induced current was reduced 46% by 5 microM methylatropine (n = 15) and 84% by 200 microM hexamethonium (n = 9). The current was linear as a function of the holding potential (extrapolated reversal potential: -22 +/- 2 mV). In conclusion, carbachol exerts both pre- and postsynaptic effects on C1 and other putative sympathoexcitatory RVLM neurons. In vitro the postsynaptic effect of carbachol has a mixed nicotinic and muscarinic pharmacology. In vivo, iontophoretically applied carbachol produces muscarinic excitation of barosensitive RVLM neurons.

Role of GABAA and GABAC Receptors in the Biphasic GABA Responses in Neurons of the Rat Major Pelvic Ganglia

1999 ◽  
Vol 82 (3) ◽  
pp. 1489-1496 ◽  
Author(s):  
Takashi Akasu ◽  
Yoshikazu Munakata ◽  
Masashi Tsurusaki ◽  
Hiroshi Hasuo
Keyword(s):  
Receptor Antagonist ◽  
Gaba Receptors ◽  
Reversal Potential ◽  
Input Resistance ◽  
Krebs Solution ◽  
Biphasic Response ◽  
Early Component ◽  
Pelvic Ganglia

The role of γ-aminobutyric acid-A (GABAA) and GABAC receptors in the GABA-induced biphasic response in neurons of the rat major pelvic ganglia (MPG) were examined in vitro. Application of GABA (100 μM) to MPG neurons produced a biphasic response, an initial depolarization (GABAd) followed by a hyperpolarization (GABAh). The input resistance of the MPG neurons was decreased during the GABAd, whereas it was increased during the GABAh. The GABAd could be further separated into the early component (early GABAd) with a duration of 27 ± 5 s (mean ± SE; n = 11) and the late component (late GABAd) with a duration of 109 ± 11 s ( n = 11). The duration of the GABAh was 516 ± 64 s ( n = 11). The effects of GABA (5–500 μM) in producing the depolarization and the hyperpolarization were concentration-dependent. GABA (5–30 μM) induced only late depolarizations. The early component of the depolarization appeared when the concentration of GABA was >50 μM. Muscimol produced only early depolarizing responses. Baclofen (100 μM) had no effect on the membrane potential and input resistance of MPG neurons. Bicuculline (60 μM) blocked the early GABAdbut not the late GABAd and the GABAh. Application of picrotoxin (100 μM) with bicuculline (60 μM) blocked both the late GABAd and the GABAh. CGP55845A (3 μM), a selective GABAB receptor antagonist, did not affect the GABA-induced responses. cis-4-Aminocrotonic acid (CACA, 1 mM) and trans-4-aminocrotonic acid (TACA, 1 mM), selective GABAC receptor agonists, produced late biphasic responses in the MPG neurons. The duration of the CACA responses was almost the same as those of the late GABAdand GABAh obtained in the presence of bicuculline. Imidazole-4-acetic acid (I4AA, 100 μM), a GABAC receptor antagonist, depressed the late GABAd and the GABAh but not the early GABAd. I4AA (100 μM) and picrotoxin (100 μM) also suppressed the biphasic response to CACA. The early GABAd and the late GABAd were reversed in polarity at −32 ± 3 mV ( n = 7) and −38 ± 2 mV ( n = 4), respectively, in the Krebs solution. The reversal potential of the GABAh was −34 ± 2 mV ( n = 4) in the Krebs solution. The reversal potentials of the late GABAd and the GABAh shifted to −20 ± 3 mV ( n = 5) and −22 ± 3 mV ( n = 5), respectively, in 85 mM Cl− solution. These results indicate that the late GABAd and the GABAh are mediated predominantly by bicuculline-insensitive, picrotoxin-sensitive GABA receptors, GABAC (or GABAAOr) receptors, in neurons of the rat MPG.

Neuronal inhibition by a GABAB receptor agonist in the rostral ventrolateral medulla of the rat

1995 ◽  
Vol 268 (2) ◽  
pp. R428-R437 ◽  
Author(s):  
Y. W. Li ◽  
P. G. Guyenet
Keyword(s):  
Receptor Agonist ◽  
Gabab Receptor ◽  
Rostral Ventrolateral Medulla ◽  
Synaptic Activity ◽  
Gabab Receptors ◽  
Ventrolateral Medulla ◽  
Gamma Aminobutyric Acid ◽  
Neuronal Inhibition

We recorded the effects of the gamma-aminobutyric acid class B (GABAB) receptor agonist baclofen on neuronal activity in the rat rostral ventrolateral medulla (RVLM) in tissue slices and in vivo. In vitro, baclofen (3 microM) produced hyperpolarization (13 of 17), decrease in input resistance (12 of 16), and reduction of spontaneous synaptic activity (7 of 14). Baclofen inhibited 84 of 87 spontaneously active neurons recorded extracellularly in vitro. Inhibition was concentration dependent (0.1-3 microM, maximum inhibition: 94 +/- 4%, n = 16) and persisted in low-Ca2+/high-Mg2+ medium (n = 19). The GABAB receptor antagonists CGP-54626A (1 microM, n = 19), CGP-55845A (1 microM, n = 15), and 2-hydroxysaclofen (0.5 mM, n = 3) attenuated inhibition by baclofen (1-3 microM) but not by muscimol or GABA. In vivo, iontophoresis of baclofen inhibited 31 of 32 RVLM neurons, including bulbospinal barosensitive (15 of 16) and respiratory ones (7 of 7). CGP-55845A attenuated baclofen inhibition (6 of 9). Bicuculline attenuated the effect of GABA but not that of baclofen (4 of 4). In summary, RVLM presympathetic neurons have somatodendritic GABAB receptors that may contribute to baclofen-induced hypotension in humans.

Dorsal and Ventral Distribution of Excitable and Synaptic Properties of Neurons of the Bed Nucleus of the Stria Terminalis

2003 ◽  
Vol 90 (1) ◽  
pp. 405-414 ◽  
Author(s):  
Regula E. Egli ◽  
Danny G. Winder
Keyword(s):  
Receptor Antagonist ◽  
Drugs Of Abuse ◽  
Input Resistance ◽  
Membrane Properties ◽  
Resting Membrane Potential ◽  
Stria Terminalis ◽  
Bed Nucleus ◽  
Adult Mice ◽  
Dependent Potential

The bed nucleus of the stria terminalis (BNST) is a structure uniquely positioned to integrate stress information and regulate both stress and reward systems. Consistent with this arrangement, evidence suggests that the BNST, and in particular the noradrenergic input to this structure, is a key component of affective responses to drugs of abuse. We have utilized an in vitro slice preparation from adult mice to determine synaptic and membrane properties of these cells, focusing on the dorsal and ventral subdivisions of the anterolateral BNST (dBNST and vBNST) because of the differential noradrenergic input to these two regions. We find that while resting membrane potential and input resistance are comparable between these subdivisions, excitable properties, including a low-threshold spike (LTS) likely mediated by T-type calcium channels and an Ih-dependent potential, are differentially distributed. Inhibitory and excitatory postsynaptic potentials (IPSPs and EPSPs, respectively) are readily evoked in both dBNST and vBNST. The fast IPSP is predominantly GABAA-receptor mediated and is partially blocked by the AMPA/kainate-receptor antagonist CNQX. In the presence of the GABAA-receptor antagonist picrotoxin, cells in dBNST but not vBNST are more depolarized and have a higher input resistance, suggesting tonic GABAergic inhibition of these cells. The EPSPs elicited in BNST are monosynaptic, exhibit paired pulse facilitation, and contain both an AMPA- and an N-methyl-d-aspartate (NMDA) receptor-mediated component. These data support the hypothesis that neurons of the dorsal and ventral BNST differentially integrate synaptic input, which is likely of behavioral significance. The data also suggest mechanisms by which information may flow through stress and reward circuits.

Effects of norepinephrine upon superficial layer neurons in the superior colliculus of the hamster: In vitro studies

1999 ◽  
Vol 16 (3) ◽  
pp. 557-570 ◽  
Author(s):  
HONGJING TAN ◽  
RICHARD D. MOONEY ◽  
ROBERT W. RHOADES
Keyword(s):  
Superior Colliculus ◽  
Optic Tract ◽  
Reversal Potential ◽  
Outward Current ◽  
Input Resistance ◽  
Superficial Layer ◽  
Membrane Properties ◽  
Induced Response

Intracellular recording techniques were used to evaluate the effects of norepinephrine (NE) on the membrane properties of superficial layer (stratum griseum superficiale and stratum opticum) superior colliculus (SC) cells. Of the 207 cells tested, 44.4% (N = 92) were hyperpolarized by ≥3 mV and 8.7% (N = 18) were depolarized by ≥3 mV by application of NE. Hyperpolarization induced by NE was dose dependent (EC50 = 8.1 μM) and was associated with decreased input resistance and outward current which had a reversal potential of −94.0 mV. Depolarization was associated with a very slight rise in input resistance and had a reversal potential of −93.1 mV for the single cell tested. Pharmacologic experiments demonstrated that isoproterenol, dobutamine, and p-aminoclonidine all hyperpolarized SC cells. These results are consistent with the conclusion that NE-induced hyperpolarization of SC cells is mediated by both α2 and β1 adrenoceptors. The α1 adrenoceptor agonists, methoxamine and phenylephrine, depolarized 35% (6 of 17) of the SC cells tested by ≥3 mV. Most of the SC cells tested exhibited responses indicative of expression of more than one adrenoceptor. Application of p-aminoclonidine or dobutamine inhibited transsynaptic responses in SC cells evoked by electrical stimulation of optic tract axons. Inhibition of evoked responses by these agents was usually, but not invariably, associated with a hyperpolarization of the cell membrane and a reduction in depolarizing potentials evoked by application of glutamate. The present in vitro results are consistent with those of the companion in vivo study which suggested that NE-induced response suppression in superficial layer SC neurons was primarily postsynaptic and chiefly mediated by both α2 and β1 adrenoceptors.

Neuronal excitation by angiotensin II in the rostral ventrolateral medulla of the rat in vitro

1995 ◽  
Vol 268 (1) ◽  
pp. R272-R277 ◽  
Author(s):  
Y. W. Li ◽  
P. G. Guyenet
Keyword(s):  
Angiotensin Ii ◽  
Excitatory Amino Acid ◽  
Rostral Ventrolateral Medulla ◽  
Ventrolateral Medulla ◽  
Ang Ii ◽  
Excitatory Amino Acid Receptor ◽  
Neuronal Excitation ◽  
Uk 14,304

We examined the effects of angiotensin II (ANG II) on spontaneous unit activity in slices of the rat rostral ventrolateral medulla (RVLM), ANG II (1-3 microM) excited 61% of a population of slowly and irregularly firing RVLM neurons (predrug, 1.2 +/- 0.1 spikes/s; postdrug, 4.6 +/- 0.3 spikes/s; n = 52). ANG II had no effect on pacemaker-like rapidly firing neurons (predrug, 8.6 +/- 0.4 spikes/s; n = 33). The effect of ANG II on slowly firing cells was repeatable and was reduced 75% by 3 microM losartan (baseline, 1.7 +/- 0.4 spikes/s; ANG II, 5.3 +/- 0.7 spikes/s; ANG II+losartan, 2.4 +/- 0.6 spikes/s; n = 12). The ongoing activity of slowly firing neurons was unaffected by 0.5-1 mM kynurenic acid (an ionotropic excitatory amino acid receptor antagonist). Most ANG II-responsive neurons (10 of 11) were inhibited by the alpha 2-adrenergic receptor agonist UK-14,304, but pacemaker-like neurons were not. In conclusion, the RVLM contains neurons excited by AT1 receptor agonists. These neurons are distinct from the previously described pacemaker nonadrenergic presympathetic cells. They may be responsible for the pressor effects produced by injecting ANG II into the RVLM in vivo.

scholarly journals Synaptic and extrasynaptic transmission of kidney-related neurons in the rostral ventrolateral medulla

2013 ◽  
Vol 110 (11) ◽  
pp. 2637-2647 ◽  
Author(s):  
Hong Gao ◽  
Andrei V. Derbenev
Keyword(s):  
Large Scale ◽  
Critical Role ◽  
Input Resistance ◽  
Rostral Ventrolateral Medulla ◽  
Kainate Receptors ◽  
Ventrolateral Medulla ◽  
Resting Membrane Potential ◽  
Arterial Blood ◽  
Whole Cell Patch Clamp ◽  
Tonic Current

The rostral ventrolateral medulla (RVLM) is a critical component of the sympathetic nervous system regulating homeostatic functions including arterial blood pressure. Using the transsynaptic retrograde viral tracer PRV-152, we identified kidney-related neurons in the RVLM. We found that PRV-152-labeled RVLM neurons displayed an unusually large persistent, tonic current to both glutamate, via N-methyl-d-aspartate (NMDA) and 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid (AMPA)/kainate receptors, and to γ-aminobutyric acid (GABA), via GABAAreceptors, in the absence of large-scale phasic neurotransmission with whole cell patch-clamp recordings. A cocktail of potent NMDA and AMPA/kainate ionotropic glutamate receptor antagonists AP-5 (50 μM) and CNQX (10 μM) revealed a two-component somatic tonic excitatory current with an overall amplitude of 42.6 ± 13.4 pA. Moreover, application of the GABAAreceptor blockers gabazine (15 μM) and bicuculline (30 μM) revealed a robust somatic tonic inhibitory current with an average amplitude of 196.3 ± 39.3 pA. These findings suggest that the tonic current plays a role in determining the resting membrane potential, input resistance, and firing rate of RVLM neurons. The magnitude of the tonic inhibitory current demonstrates that GABAergic inhibition plays a critical role in regulation of kidney-related RVLM neurons. Our results indicate that the GABAergic tonic current may determine the basal tone of firing activity in kidney-related RVLM neurons.

scholarly journals Rhythmic Properties of Neurons in the Rostral Ventrolateral Medulla of the Rat In Vitro: Effects of Clonidine

2002 ◽  
Vol 88 (5) ◽  
pp. 2262-2279 ◽  
Author(s):  
Antonio R. Granata ◽  
Morton I. Cohen
Keyword(s):  
Interspike Interval ◽  
Rostral Ventrolateral Medulla ◽  
Ventrolateral Medulla ◽  
Type I ◽  
Slice Preparation ◽  
Different Populations ◽  
In Vitro Effects ◽  
Spike Firing

The rostral ventrolateral medulla (RVLM) is thought to be the main central site for generation of tonic sympathetic activity. In the rat in vitro slice preparation, we used intracellular recordings to identify different populations of neurons in the RVLM: 43 spontaneously active neurons with regular (R) or irregular (I) patterns of spike firing and 10 silent neurons. The degree of regularity was quantified by the coefficient of variation (CV = SD/mean) of interspike interval durations, as well as by the rhythmic properties of the spike autospectrum and autocorrelation. The distribution of CVs was clustered: R and I neurons were defined as those with CVs ≤12% ( n = 21) or >12% ( n = 22), respectively. The R-type and I-type neurons resemble the type II and type I neurons, respectively, which were previously characterized in the RVLM in vivo as barosensitive and bulbospinal. Both types may be important in generation of sympathetic tone. Clonidine (1–100 μM) was applied to 10 R-type neurons and 16 I-type neurons. The firing of 21/26 was depressed to the point of silence. However, 18/26 neurons were excited earlier in the perfusion. The later depression of firing occurred in both I and R neurons and in different cases was associated with either hyperpolarization or depolarization.

Sign in / Sign up

Export Citation Format

Share Document