scholarly journals Dopamine effects on identified rat vagal motoneurons

2007 ◽  
Vol 292 (4) ◽  
pp. G1002-G1008 ◽  
Author(s):  
Zhongling Zheng ◽  
R. Alberto Travagli
Keyword(s):  
Tyrosine Hydroxylase ◽  
Brain Stem ◽  
Nucleus Tractus Solitarius ◽  
Sch 23390 ◽  
Membrane Properties ◽  
Whole Cell ◽  
Catecholaminergic Neurons ◽  
Whole Cell Recordings ◽  
Brain Stem Slices ◽  
Stem Slices

Catecholaminergic neurons of the A2 area play a prominent role in brain stem vagal circuits. It is not clear, however, whether these neurons are noradrenergic or adrenergic, i.e., display tyrosine hydroxylase (TH) and dopamine-β-hydroxylase (DβH) immunoreactivity (-IR) or dopaminergic (i.e., TH- but not DβH-IR). Our aims were to investigate whether a subpopulation of neurons in the A2 area was dopaminergic and, if so, to investigate the effects of dopamine (DA) on the membrane of gastric-projecting vagal motoneurons. We observed that although the majority of A2 neurons were both TH- and DβH-IR, a small percentage of nucleus tractus solitarius neurons were TH-IR only, suggesting that DA itself may play role in these circuits. Whole cell recordings from thin brain stem slices showed that 71% of identified gastric-projecting motoneurons responded to DA (1–300 μM) with either an excitation (28%) or an inhibition (43%) of the membrane; the remaining 29% of the neurons were unresponsive. The DA-induced depolarization was mimicked by SK 38393 and prevented by pretreatment with SCH 23390. Conversely, the DA-induced inhibition was mimicked by bromoergocryptine and prevented by pretreatment with L741626. When tested on the same neuron, the effects of DA and NE were not always similar. In fact, in neurons in which DA induced a membrane depolarization, 77% were inhibited by NE, whereas 75% of neurons unresponsive to DA were inhibited by NE. Our data suggest that DA modulates the membrane properties of gastric-projecting motoneurons via D1- and D2-like receptors, and DA may play different roles than norepinephrine in brain stem vagal circuits.

Urethane inhibits the GABAergic neurotransmission in the nucleus of the solitary tract of rat brain stem slices

2007 ◽  
Vol 292 (1) ◽  
pp. R396-R402 ◽  
Author(s):  
Daniela Accorsi-Mendonça ◽  
Ricardo M. Leão ◽  
José F. Aguiar ◽  
Wamberto A. Varanda ◽  
Benedito H. Machado
Keyword(s):  
Brain Stem ◽  
Inhibitory Effect ◽  
Membrane Properties ◽  
Solitary Tract ◽  
Patch Clamp Technique ◽  
Gabaergic Neurotransmission ◽  
Postsynaptic Currents ◽  
Excitatory Responses ◽  
Brain Stem Slices ◽  
Stem Slices

Because urethane is a widely used anesthetic in animal experimentation, in the present study, we evaluated its effects on neurons of the nucleus of the solitary tract (NTS) in brain stem slices from young rats (25–30 days old). Using the whole cell configuration of the patch-clamp technique, spontaneous postsynaptic currents (sPSCs) and evoked excitatory postsynaptic currents (eEPSCs) were recorded. Urethane (20 mM) decreased by ∼60% the frequency of GABAergic sPSCs (1.0 ± 0.2 vs. 0.4 ± 0.1 Hz) but did not change the frequency, amplitude, or half-width of glutamatergic events or TTX-resistant inhibitory sPSCs [miniature inhibitory postsynaptic currents (IPSCs)]. Miniature IPSCs were measured in the presence of urethane plus 1 mM diazepam (1 mM), and no changes were seen in their amplitude. This suggests that the GABA concentration in the NTS synapses is set at saturating level. We also evaluated the effect of urethane on eEPSCs, and no significant change was observed in the amplitude of N-methyl-d-aspartate [NMDA; 44.2 ± 11.5 vs. 37.6 ± 10.6 pA (holding potential = 40 mV)] and non-NMDA currents [204.4 ± 35.5 vs. 196.6 ± 31.2 pA (holding potential = −70 mV)]. Current-clamp experiments showed that urethane did not alter the action potential characteristics and passive membrane properties. These data suggest that urethane has an inhibitory effect on GABAergic neurons in the NTS but does not change the spontaneous or evoked excitatory responses.

Two Types of Actions of Norepinephrine on Identified Auditory Efferent Neurons in Rat Brain Stem Slices

1997 ◽  
Vol 78 (4) ◽  
pp. 1800-1810 ◽  
Author(s):  
Xueyong Wang ◽  
Donald Robertson
Keyword(s):  
Brain Stem ◽  
Rat Brain ◽  
Inhibitory Response ◽  
Current Clamp ◽  
Inward Current ◽  
Current Clamp Mode ◽  
Efferent Neurons ◽  
Auditory Efferent ◽  
Brain Stem Slices ◽  
Stem Slices

Wang, Xueyong and Donald Robertson. Two types of actions of norepinephrine on identified auditory efferent neurons in rat brain stem slices. J. Neurophysiol. 78: 1800–1810, 1997. Whole cell voltage-clamp recordings were performed on auditory olivocochlear neurons in the ventral nucleus of the trapezoid body (VNTB) of brain stem slices from neonatal rats. Each neuron was identified by retrograde labeling with Fast Blue injected into the cochlea. Bath application of norepinephrine (NE; 1–10 μM) reversibly induced an inward current in 26 of 38 labeled neurons that were voltage clamped at −75 mV. This was responsible for the membrane depolarization to NE observed in current-clamp mode. The NE-induced inward current appeared to be more prominent at −55 mV than at −75 mV and reversed at around −100 mV. It was attenuated but not prevented by 20 mM tetraethylammonium, and it persisted when the perfusate contained 2 mM Cs+ or 100 μM Cd2+. However, the NE-induced inward current was attenuated to varying degrees in a zero-Ca2+ solution. Current-voltage plots revealed that NE caused a decrease in membrane K+ conductance. A suppression of voltage-gated Ca2+ currents by NE was also observed. The excitatory action of NE was blocked by the α-adrenoreceptor antagonist phentolamine. The α1-adrenoreceptor agonist phenylephrine had an effect similar to that of NE. In 6 of 38 labeled neurons, an inhibitory action of NE (1–10 μM) was observed that appeared to be due to an activation of an inwardly rectified K+ current, which caused hyperpolarization of resting membrane potentials in current-clamp mode. This inhibitory response was independent of external Ca2+ and was abolished by 2–5 mM Cs+ or 0.5 mM Ba2+ applied in the perfusate. The receptors involved in the inhibitory actions of NE are not clear. The effect was partially and reversibly blocked by propranolol (10 μM), a β-adrenoreceptor antagonist. However, isoprenaline (10 μM), a β-adrenoreceptor agonist, failed to induce any effect. On the other hand, the inhibitory effect was irreversibly blocked by pretreatment with phentolamine (5–10 μM). Phenylephrine (5–10 μM) had no effect.

Substance P-Induced Inward Current in Identified Auditory Efferent Neurons in Rat Brain Stem Slices

1998 ◽  
Vol 80 (1) ◽  
pp. 218-229 ◽  
Author(s):  
Xueyong Wang ◽  
Donald Robertson
Keyword(s):  
Substance P ◽  
Brain Stem ◽  
Rat Brain ◽  
Inward Rectifier ◽  
Equilibrium Potential ◽  
Inward Current ◽  
Efferent Neurons ◽  
Auditory Efferent ◽  
Brain Stem Slices ◽  
Stem Slices

Wang, Xueyong and Donald Robertson. Substance P-induced inward current in identified auditory efferent neurons in rat brain stem slices. J. Neurophysiol. 80: 218–229, 1998. The effects of substance P (SP) on whole cell currents were studied in neurons of the medial olivocochlear efferent system (MOCS) in the ventral nucleus of the trapezoid body (VNTB) of brain stem slices from neonatal rats. Each neuron was identified by retrograde labeling with Fast Blue injected into the cochlea. Bath application of SP (0.1–10 μM) reversibly induced an apparent inward current in 49 of 63 labeled neurons when voltage clamped at near resting voltages. This apparent inward current was consistent with the SP-induced membrane depolarization observed in current-clamp mode. The SP-induced change in current was dose dependent with a half-maximal response dose of 200 nM. It was mimicked by [Cys3,6, Tyr8, Pro9]-SP, a neurokinin (NK1) receptor selective agonist, whereas [Succinyl-Asp6, MePhe8]-SP 6–11 (Senktide), a NK3 receptor agonist, had no detectable effect. The SP effect was not blocked by 10-6 M tetrodotoxin (TTX) and persisted when the perfusate contained 30 mM tetraethylammonium (TEA) or 100 μM Cd2+ or was in a 0-Ca solution. In a TTX-containing solution, SP caused a voltage-dependent decrease of membrane conductance, and the SP-evoked current reversed at a potential at around −105 mV. The predicted K+ equilibrium potential was −93.8 mV under the experimental conditions. The SP-induced inward current was attenuated by 66% when the perfusate contained 3 mM Cs+. We conclude that the apparent inward current is partly caused by SP decreasing an outward current normally maintained by the inward rectifier K+ channels in these cells. In the presence of Cs solution in the recording pipette and with a perfusate containing 3 mM Cs+, 0.1 mM Cd2+ and 10-6 M TTX, a residual SP-induced inward current was observed at test voltages ranging from −120 to 40 mV. This subcomponent reversed its polarity at ∼20 mV. This inward current was reduced substantially (but not abolished) when all NaCl in the external solution was replaced by TEA-Cl. The results indicate that SP also opens an unknown cation channel, which the available data suggests may be relatively nonselective. The results suggest that MOCS neurons are subject to modulation by SP, which depolarizes the cell membrane by decreasing the activity of inward rectifier K+ channels as well as concurrently activating a separate cation conductance. It also was found that in MOCS neurons responsive to both SP and norepinephrine, the norepinephrine effect was abolished by TTX, suggesting that an interneuronal population excited by norepinephrine converges selectively onto SP-sensitive MOCS neurons in the VNTB.

Membrane properties of dentate gyrus granule cells: comparison of sharp microelectrode and whole-cell recordings

1992 ◽  
Vol 67 (5) ◽  
pp. 1346-1358 ◽  
Author(s):  
K. J. Staley ◽  
T. S. Otis ◽  
I. Mody
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Dentate Gyrus ◽  
Granule Cells ◽  
Dendritic Tree ◽  
Membrane Voltage ◽  
Membrane Properties ◽  
Whole Cell ◽  
Calcium Buffers ◽  
Whole Cell Recordings

1. Whole-cell and sharp electrode recordings from adult rat dentate gyrus GCs were performed in the 400-microns-thick hippocampal slice preparation maintained at 34 +/- 1 degrees C. Intrinsic membrane properties of granule cells (GCs) were evaluated with the use of a switching current-clamp amplifier. 2. With the whole-cell technique, the average resting membrane potential (RMP) of GCs was -85 mV when a potassium gluconate electrode solution was used versus -74 mV measured with potassium acetate-filled sharp microelectrodes. The membrane voltage response to injected current was linear over two membrane potential ranges, greater than 10 mV hyperpolarized from RMP and between 10 mV more negative than RMP and -62 mV. The average input resistances (RN) calculated over these ranges were 107 and 228 M omega in the whole-cell recordings versus 37 and 54 M omega in the sharp electrode recordings. There was no correlation between RMP and RN with either recording technique. The membrane time constant (tau m) determined at the RMP was 26.9 ms for whole-cell recordings and 13.9 ms for sharp electrode recordings. 3. There was no evidence of time-dependent changes in RMP, RN, and tau m in whole-cell recordings, although the slow inward rectification seen at hyperpolarized potentials decreased over 30-60 min. Addition of calcium buffers to the whole-cell recording solution did not result in a significant change in the average RMP, the average RN, or the average tau m. 4. Action potential threshold was comparable in whole-cell (-49 mV) and sharp electrode (-52 mV) recordings, but action potential amplitude was larger in whole-cell (126 mV) than in sharp electrode (106 mV) recordings. Spike frequency adaptation was present in the whole-cell recordings and could be abolished by addition of calcium buffers to the electrode solution. 5. We estimated rho, the ratio of dendritic to somatic conductance, to be 5.1 for the whole-cell records and 2.1 for sharp electrode recordings. The electrotonic length of the equivalent cylinder representing the cell processes was estimated to be 0.49 from the whole-cell data and 0.79 from the sharp electrode recordings. This implies that at rest there is only a 10% decrement in steady-state membrane voltage along the length of the dendrite due to shunting across the membrane resistance; small synaptic events occurring in the distal dendritic tree will therefore have a more substantial influence on the soma than previous analyses suggested.(ABSTRACT TRUNCATED AT 400 WORDS)

Optical illustration of glutamate-induced cell swelling coupled with membrane depolarization in embryonic brain stem slices

Neuroreport ◽  
1997 ◽  
Vol 8 (16) ◽  
pp. 3559-3563 ◽  
Author(s):  
Katsushige Sato ◽  
Yoko Momose-Sato ◽  
Yoshiyasu Arai ◽  
Akihiko Hirota ◽  
Kohtaro Kamino
Keyword(s):  
Brain Stem ◽  
Membrane Depolarization ◽  
Cell Swelling ◽  
Embryonic Brain ◽  
Brain Stem Slices ◽  
Stem Slices

scholarly journals Vagally mediated effects of brain stem dopamine on gastric tone and phasic contractions of the rat

2017 ◽  
Vol 313 (5) ◽  
pp. G434-G441 ◽  
Author(s):  
L. Anselmi ◽  
L. Toti ◽  
C. Bove ◽  
R. A. Travagli
Keyword(s):  
Receptor Antagonist ◽  
Brain Stem ◽  
Sch 23390 ◽  
Systemic Administration ◽  
Membrane Properties ◽  
Receptor Subtype ◽  
Motor Nucleus ◽  
Gastric Tone ◽  
Dorsal Motor Nucleus ◽  
The Brain

Dopamine (DA)-containing fibers and neurons are embedded within the brain stem dorsal vagal complex (DVC); we have shown previously that DA modulates the membrane properties of neurons of the dorsal motor nucleus of the vagus (DMV) via DA1 and DA2 receptors. The vagally dependent modulation of gastric tone and phasic contractions, i.e., motility, by DA, however, has not been characterized. With the use of microinjections of DA in the DVC while recording gastric tone and motility, the aims of the present study were 1) assess the gastric effects of brain stem DA application, 2) identify the DA receptor subtype, and, 3) identify the postganglionic pathway(s) activated. Dopamine microinjection in the DVC decreased gastric tone and motility in both corpus and antrum in 29 of 34 rats, and the effects were abolished by ipsilateral vagotomy and fourth ventricular treatment with the selective DA2 receptor antagonist L741,626 but not by application of the selective DA1 receptor antagonist SCH 23390. Systemic administration of the cholinergic antagonist atropine attenuated the inhibition of corpus and antrum tone in response to DA microinjection in the DVC. Conversely, systemic administration of the nitric oxide synthase inhibitor nitro-l-arginine methyl ester did not alter the DA-induced decrease in gastric tone and motility. Our data provide evidence of a dopaminergic modulation of a brain stem vagal neurocircuit that controls gastric tone and motility. NEW & NOTEWORTHY Dopamine administration in the brain stem decreases gastric tone and phasic contractions. The gastric effects of dopamine are mediated via dopamine 2 receptors on neurons of the dorsal motor nucleus of the vagus. The inhibitory effects of dopamine are mediated via inhibition of the postganglionic cholinergic pathway.

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