Activation of δ-Opioid Receptors Excites Spinally Projecting Locus Coeruleus Neurons Through Inhibition of GABAergic Inputs

2002 ◽  
Vol 88 (5) ◽  
pp. 2675-2683 ◽  
Author(s):  
Yu-Zhen Pan ◽  
De-Pei Li ◽  
Shao-Rui Chen ◽  
Hui-Lin Pan
Keyword(s):  
Locus Coeruleus ◽  
Dorsal Horn ◽  
Opioid Receptors ◽  
Brain Slices ◽  
Gaba Release ◽  
Current Clamp ◽  
Excitatory Effect ◽  
Inhibitory System ◽  
Postsynaptic Currents

Stimulation of the noradrenergic nucleus locus coeruleus (LC) releases norepinephrine in the spinal cord, which inhibits dorsal horn neurons and produces analgesia. Activation of this descending noradrenergic pathway also contributes to the analgesic action produced by systemic opioids. The δ-opioid receptors are present presynaptically in the LC. However, their functional role in the control of the activity of spinally projecting LC neurons remains uncertain. In this study, we tested the hypothesis that activation of presynaptic δ-opioid receptors excites spinally projecting LC neurons through inhibition of GABA release. Spinally projecting LC neurons were retrogradely labeled by a fluorescent dye, DiI, injected into the spinal dorsal horn of rats. Whole cell voltage- and current-clamp recordings were performed on DiI-labeled LC neurons in brain slices in vitro. Retrogradely labeled LC noradrenergic neurons were demonstrated by dopamine-β-hydroxylase immunofluorescence. [d-Pen2,d-Pen5]-enkephalin (DPDPE, 1 μM) significantly decreased the frequency of GABA-mediated miniature inhibitory postsynaptic currents (IPSCs) of nine DiI-labeled LC neurons from 2.1 ± 0.5 to 0.7 ± 0.2 Hz without altering their amplitude and the kinetics. On the other hand, the miniature excitatory postsynaptic currents (EPSC) of nine DiI-labeled LC neurons were not significantly altered by DPDPE. Furthermore, DPDPE significantly inhibited the amplitude of evoked IPSC but not EPSC in eight DiI-labeled LC neurons. Under the current-clamp condition, the firing activity in 9 of 11 DiI-labeled LC neurons was significantly increased by 1 μM DPDPE from 4.6 ± 0.7 to 6.2 ± 1.0 Hz. Bicuculline (20 μM) also significantly increased the firing frequency in 13 of 20 neurons from 1.8 ± 0.5 to 2.8 ± 0.6 Hz. Additionally, the excitatory effect of DPDPE on LC neurons was diminished in the presence of bicuculline. Collectively, these data strongly suggest that activation of presynaptic δ-opioid receptors by DPDPE excites a population of spinally projecting LC neurons by preferential inhibition of GABA release. Thus presynaptic δ-opioid receptors likely play an important role in the regulation of the excitability of spinally projecting LC neurons and the descending noradrenergic inhibitory system.

scholarly journals Cestode larvae excite host neuronal circuits via glutamatergic signaling

2019 ◽  
Author(s):  
Hayley Tomes ◽  
Anja de Lange ◽  
Ulrich Fabien Prodjinotho ◽  
Siddhartha Mahanty ◽  
Katherine Smith ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Imaging Techniques ◽  
Taenia Solium ◽  
Brain Slices ◽  
Receptor Activation ◽  
Excitatory Effect ◽  
Excitatory Neurotransmitter ◽  
Acquired Epilepsy ◽  
The Brain

AbstractNeurocysticercosis (NCC) is caused by the presence of Taenia solium larvae in the brain and is the leading cause of adult-acquired epilepsy worldwide. However, little is known about how seizures emerge in NCC. To address this knowledge gap we used whole-cell patch-clamp electrophysiology and calcium imaging in rodent hippocampal organotypic slice cultures to identify direct effects of cestode larval products on neuronal activity. We found both whole cyst homogenate and excretory/secretory (E/S) products of Taenia larvae have an acute excitatory effect on neurons, which trigger seizure-like events in vitro. Underlying this effect was Taenia-induced neuronal depolarization, which was mediated by glutamate receptor activation but not by nicotinic acetylcholine receptors, acid-sensing ion channels nor Substance P. Glutamate assays revealed the homogenate of both Taenia crassiceps and Taenia solium larvae contained high concentrations of glutamate and that larvae of both species consistently produce and release this excitatory neurotransmitter into their immediate environment. These findings contribute towards the understanding of seizure generation in NCC.Author summaryBrain infection by larvae of the tapeworm Taenia solium (neurocysticercosis or NCC) is the leading cause of acquired epilepsy in adulthood. Little is understood about the mechanisms by which larvae cause seizures. To address this, we used electrophysiological and imaging techniques in rodent brain slices to investigate how tapeworm larvae directly impact neuronal function. We discovered that both the homogenate and secretory products of tapeworm larvae excite neurons and can trigger seizure-like events in brain slices. This effect was caused by the activation of glutamate receptors and not by activating other types of receptors in the brain. Finally, we observed that tapeworm larvae both contain and release the neurotransmitter glutamate into their immediate environment. These findings are relevant for understanding how tapeworm larvae cause seizures in NCC.

scholarly journals Local Opiate Withdrawal in Locus Coeruleus Neurons In Vitro

2001 ◽  
Vol 85 (6) ◽  
pp. 2388-2397 ◽  
Author(s):  
Alexander Ivanov ◽  
Gary Aston-Jones
Keyword(s):  
Protein Kinase ◽  
Locus Coeruleus ◽  
Protein Kinase A ◽  
Discharge Rate ◽  
Brain Slices ◽  
Opiate Withdrawal ◽  
Spontaneous Discharge ◽  
Chronic Morphine ◽  
Kinase A

Noradrenergic neurons of the brain nucleus locus coeruleus (LC) become hyperactive during opiate withdrawal. It has been uncertain to what extent such hyperactivity reflects changes in intrinsic properties of these cells. The effects of withdrawal from chronic morphine on the activity of LC neurons were studied using intracellular recordings in rat brain slices. LC neurons in slices from chronically morphine-treated rats exhibited more than twice the frequency of spontaneous action potentials after naloxone compared with LC neurons from control rats. However, after naloxone treatment, the resting membrane potential (MP) of LC neurons from dependent rats was not significantly different from that in control rats. Neither resting MP nor spontaneous discharge rate (SDR) was altered by naloxone in LC neurons from control rats. Neither kynurenic acid nor a cocktail of glutamate and GABA antagonists (6-cyano-7-nitroquinoxalene-2,3-dione + 2-amino-5-phosphonopentanoic acid + bicuculline) blocked the hyperactivity of LC neurons precipitated by naloxone in slices from morphine-dependent rats. The effects of ouabain on MP and SDR were similar in LC neurons from control and morphine-dependent rats. These results indicate that an adaptive change in glutamatergic or GABAergic synaptic mechanisms or altered Na/K pump activity does not underlie the withdrawal-induced activation of LC neurons in vitro. Specific inhibitors of protein kinase A [Rp-cAMPS or N-(2-[p-bromocinnamylamino]ethyl)-5-isoquinolinesulfonamide (H-89)] partially suppressed the withdrawal hyperactivity of LC neurons, and activators of cAMP (forskolin) or protein kinase A (Sp-cAMPS) increased the discharge rate of LC neurons from control rats. These results suggest that upregulation of cAMP-dependent protein kinase A during chronic morphine treatment is involved in the withdrawal-induced hyperactivity of LC neurons.

Abstract P109: Activation Of Hypothalamic Glutamate Receptors Is Required For Angiotensin II-elicited Hypertensive Response Sensitization (HTRS) In Rats

Hypertension ◽  
2020 ◽  
Vol 76 (Suppl_1) ◽  
Author(s):  
Baojian Xue ◽  
Hua Zhang ◽  
Terry Beltz ◽  
De-Pei Li ◽  
Alan Johnson
Keyword(s):  
Glutamate Receptors ◽  
Brain Slices ◽  
Renin Angiotensin System ◽  
Retrograde Transport ◽  
Ventrolateral Medulla ◽  
Ang Ii ◽  
Excitatory Effect ◽  
Functional Studies ◽  
Pre Treatment

Hypertension is associated with sympathetic nervous system activation, which involves interactions between the renin-angiotensin system and glutamatergic mechanisms in the hypothalamic paraventricular nucleus (PVN). Using the Induction-Delay-Expression (IND-DEL-EXP) experimental paradigm, our previous studies demonstrated that administration of a subpressor dose of angiotensin (ANG) II (10 ng/kg/min) during IND sensitizes subsequent ANG II (120 ng/kg/min)-elicited hypertension during EXP. Systemic or intracerebroventricular administration of glutamatergic NMDA-R antagonists (MK801 and AP5) during the IND period abolishes the IND of ANG II-elicited hypertensive response sensitization (HTRS). In the present study, we investigated further the role of hypothalamic glutamate and glutamate receptors (GluRs) in ANG II-elicited HTRS. First, PVN neurons to be studied in vitro were back-labelled by a tracer injected into the rostral ventrolateral medulla (RVLM). After sufficient time for retrograde transport, the rats were treated with a subpressor dose of ANG II sufficient to induce HTRS. In PVN brain slices studied following DEL, basal firing activities of PVN-RVLM projecting neurons did not differ between rats treated with saline and rats treated with a subpressor dose of ANG II. However, bath application of ANG II (2.0 μM) induced a significant increase in the firing rate of PVN-RVLM neurons in rats treated with ANG II during IND as compared to saline treated controls. This enhanced excitatory effect of ANG II on PVN-RVLM neurons was blocked by an NMDAR antagonist, AP5 (50 μM). Pre-treatment with the subpressor dose of ANG II during IND also significantly increased evoked NMDAR- excitatory postsynaptic currents in PVN-RVLM neurons. In functional studies, we found that bilateral PVN microinjections of glutamate (100 nm, 100 nl) during IND produced HTRS whereas PVN vehicle injections did not (Δ50.8±3.2 vs Δ20.8±6.5 mmHg). Taken together, our findings indicate that GluR activation in the PVN is sufficient and necessary for the IND of ANG II-elicited HTRS. The results indicate that a sustained increase in excitability of PVN-RVLM projecting neurons is likely to play an important role in maintaining the CNS state that produces HTRS.

Differential ontogenesis of presynaptic and postsynaptic GABAB inhibition in rat somatosensory cortex

1993 ◽  
Vol 70 (1) ◽  
pp. 448-452 ◽  
Author(s):  
A. Fukuda ◽  
I. Mody ◽  
D. A. Prince
Keyword(s):  
Somatosensory Cortex ◽  
Gabab Receptor ◽  
Age Groups ◽  
Brain Slices ◽  
Gaba Release ◽  
Equilibrium Potential ◽  
Gamma Aminobutyric Acid ◽  
Postnatal Maturation ◽  
Rat Somatosensory Cortex

1. The postnatal maturation of gamma-aminobutyric acid (GABA)B receptor-mediated presynaptic inhibition was studied in brain slices of rat somatosensory cortex maintained in vitro. Patchclamp techniques were used to record whole-cell inhibitory post-synaptic currents from layer II-III neurons in animals from postnatal days (P) 7-24. Monosynaptic inhibitory postsynaptic currents (IPSCs) were evoked after N-methyl-D-aspartate (NMDA) and non-NMDA type glutamate receptors had been blocked by D-amino-phosphonovaleric acid (D-AP5, 20 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 10 microM), respectively. These IPSCs were solely mediated by postsynaptic GABAA receptors because they were abolished by bicuculline (10 microM), reversed polarity near the chloride equilibrium potential, and were recorded with electrodes that contained Cs+ to block postsynaptic GABAB responses. 2. When pairs of stimuli separated by intervals of 0.1-10 s were used to evoke IPSCs, the second response was depressed, an effect that was maximal at 300 ms. Evoked IPSCs were also depressed by baclofen (10 microM). The paired pulse depression (PPD) of monosynaptic IPSCs was decreased or eliminated by 2-OH-saclofen (200 microM). These findings indicate that PPD of monosynaptic IPSCs was due to presynaptic GABAB receptor-mediated inhibition of GABA release. 3. There were no significant differences in the amounts of PPD in neurons from different age groups (P7-10, P12-17, P22-24) at any interstimulus interval tested (0.1-10 s).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin-like growth factor 1 (IGF-1) increases GABAergic neurotransmission to GnRH neurons via suppressing the retrograde tonic endocannabinoid signaling pathway in mice

2020 ◽  
Author(s):  
Flora Balint ◽  
Veronika Csillag ◽  
Csaba Vastagh ◽  
Zsolt Liposits ◽  
Imre Farkas
Keyword(s):  
Growth Factor ◽  
Transient Receptor Potential ◽  
Brain Slices ◽  
Fine Tuning ◽  
Transient Receptor Potential Vanilloid ◽  
Insulin Like Growth Factor ◽  
Gabaergic Neurotransmission ◽  
Postsynaptic Currents ◽  
Gnrh Neurons

Introduction: Hypophysiotropic gonadotropin releasing-hormone (GnRH) neurons orchestrate various physiological events that control the onset of puberty. Previous studies showed that insulin-like growth factor 1 (IGF-1) induces the secretion of GnRH and accelerates the onset of puberty, suggesting a regulatory role of this hormone upon GnRH neurons. Methods: To reveal responsiveness of GnRH neurons to IGF-1 and elucidate molecular pathways acting downstream to the IGF-1 receptor (IGF-1R), in vitro electrophysiological experiments were carried out on GnRH-GFP neurons in acute brain slices from prepubertal (23-29 days) and pubertal (50-day) male mice. Results: Administration of IGF-1 (13 nM) significantly increased the firing rate and frequency of spontaneous postsynaptic currents (sPSCs), and that of excitatory GABAergic miniature postsynaptic currents (mPSCs). No GABAergic mPSCs were induced by IGF-1 in the presence of GABAA-R blocker picrotoxin. The increase in the mPSC frequency was prevented by the use of IGF-1R antagonist, JB1 (1 µM) or the intracellularly applied PI3K blocker (LY294002, 50 µM) showing involvement of IGF-1R and PI3K in the mechanism. Blockade of the transient receptor potential vanilloid 1 (TRPV1), an element of the tonic retrograde endocannabinoid machinery by AMG9810 (10 µM) or antagonizing cannabinoid receptor type-1 (CB1) by AM251 (1 µM) abolished the effect. Discussion/Conclusion: These findings indicate that IGF-1 arrests the tonic retrograde endocannabinoid pathway in GnRH neurons and this disinhibition increases the release of GABA from presynaptic terminals that, in turn, activates GnRH neurons leading to the fine-tuning of the hypothalamo-pituitary-gonadal axis.

Characterization of a developmentally transient adrenergic depolarizing response in cultured locus coeruleus neurons

1988 ◽  
Vol 66 (12) ◽  
pp. 1547-1554 ◽  
Author(s):  
Paul G. Finlayson ◽  
Kenneth C. Marshall
Keyword(s):  
Locus Coeruleus ◽  
Adrenergic Receptors ◽  
Divalent Cations ◽  
Brain Slices ◽  
Postnatal Period ◽  
Selective Antagonists ◽  
Electrophysiological Studies

The effects of iontophoretically applied noradrenaline have been tested on intracellularly recorded locus coeruleus neurons grown in explant cultures from neonatal mice. In addition to hyperpolarizing responses mediated by α2-adrenergic receptors, as observed in locus coeruleus neurons in vivo and in brain slices from adult animals, α1-mediated depolarizations were observed to succeed the initial hyperpolarizations in some cultures. It was shown that the depolarizing responses were only present in younger cultures, i.e., less than 26 days in vitro. In cultures less than 20 days old, all cells displayed the biphasic hyperpolarizing-depolarizing responses. Both components of the response appear to be direct, since they were present when synaptic transmission was blocked by including tetrodotoxin or by altering divalent cations in the perfusate. The depolarizing responses were frequently reduced in solutions with altered divalent cation content, and this might reflect a calcium dependency of this response. The hyperpolarizing and depolarizing components of the responses to noradrenaline were progressively blocked by increasing concentrations of the selective antagonists yohimbine and prazosin, respectively, in the dose ranges of 100 nM – 1 μM (yohimbine) and 20–200 nM (prazosin). Recent results from electrophysiological studies of locus coeruleus neurons in brain slices suggest that similar changes occur in the animal as well as in culture. It is possible that the transient depolarizing responses reflect a developmentally important enhanced responsiveness of locus coeruleus neurons during the early postnatal period.

scholarly journals Desensitization-resistant and -sensitive GPCR-mediated inhibition of GABA release occurs by Ca2+-dependent and -independent mechanisms at a hypothalamic synapse

2016 ◽  
Vol 115 (5) ◽  
pp. 2376-2388 ◽  
Author(s):  
Reagan L. Pennock ◽  
Shane T. Hentges
Keyword(s):  
G Protein ◽  
Opioid Receptors ◽  
Transmitter Release ◽  
Presynaptic Inhibition ◽  
Calcium Influx ◽  
Gaba Release ◽  
Presynaptic Receptors ◽  
Postsynaptic Currents ◽  
Independent Mechanism ◽  
Μ Opioid Receptors

Whereas the activation of Gαi/o-coupled receptors commonly results in postsynaptic responses that show acute desensitization, the presynaptic inhibition of transmitter release caused by many Gαi/o-coupled receptors is maintained during agonist exposure. However, an exception has been noted where GABAB receptor (GABABR)-mediated inhibition of inhibitory postsynaptic currents (IPSCs) recorded in mouse proopiomelanocortin (POMC) neurons exhibit acute desensitization in ∼25% of experiments. To determine whether differential effector coupling confers sensitivity to desensitization, voltage-clamp recordings were made from POMC neurons to compare the mechanism by which μ-opioid receptors (MORs) and GABABRs inhibit transmitter release. Neither MOR- nor GABABR-mediated inhibition of release relied on the activation of presynaptic K+ channels. Both receptors maintained the ability to inhibit release in the absence of external Ca2+ or in the presence of ionomycin-induced Ca2+ influx, indicating that inhibition of release can occur through a Ca2+-independent mechanism. Replacing Ca2+ with Sr2+ to disrupt G-protein-mediated inhibition of release occurring directly at the release machinery did not alter MOR- or GABAB -mediated inhibition of IPSCs, suggesting that reductions in evoked release can occur through the inhibition of Ca2+ channels. Additionally, both receptors inhibited evoked IPSCs in the presence of selective blockers of N- or P/Q-type Ca2+ channels. Altogether, the results show that MORs and GABABRs can inhibit transmitter release through the inhibition of calcium influx and by direct actions at the release machinery. Furthermore, since both the desensitizing and nondesensitizing presynaptic receptors are similarly coupled, differential effector coupling is unlikely responsible for differential desensitization of the inhibition of release.

Modulation of Synaptic Transmission in the Rat Nucleus of the Solitary Tract by Endomorphin-1

2005 ◽  
Vol 93 (5) ◽  
pp. 2530-2540 ◽  
Author(s):  
Nicholas R. Glatzer ◽  
Bret N. Smith
Keyword(s):  
Synaptic Transmission ◽  
Opioid Receptors ◽  
Nucleus Tractus Solitarius ◽  
Integration Site ◽  
Brain Slices ◽  
Inhibitory Neurons ◽  
Solitary Tract ◽  
Endogenous Opioid ◽  
Opioid Agonist ◽  
Postsynaptic Currents

Activation of opioid receptors in the periphery and centrally in the brain results in inhibition of gastric and other vagally mediated functions. The aim of this study was to examine the role of the endogenous opioid agonist endomorphin 1 (EM-1) in regulating synaptic transmission within the nucleus tractus solitarius (NTS), an integration site for autonomic functions. We performed whole cell patch-clamp recordings from coronal brain slices of the rat medulla. A subset of the neurons studied was prelabeled with a stomach injection of the transsynaptic retrograde virus expressing EGFP, PRV-152. Solitary tract stimulation resulted in constant latency excitatory postsynaptic currents (EPSCs) that were decreased in amplitude by EM-1 (0.01–10 μM). The paired-pulse ratio was increased with little change in input resistance, suggesting a presynaptic mechanism. Spontaneous EPSCs were decreased in both frequency and amplitude by EM-1, and miniature EPSCs were reduced in frequency but not amplitude, suggesting a presynaptic mechanism for the effect. Spontaneous inhibitory postsynaptic currents (IPSCs) were also reduced in frequency by EM-1, but the effect was blocked by TTX, suggesting activity at receptors on the somata of local inhibitory neurons. Synaptic input arising from local NTS neurons, which were activated by focal photolysis of caged glutamate, was inhibited by EM-1. The actions of EM-1 were similar to those of d-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO) and were blocked by naltrexone, d-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP), or d-Phe-Cys-Tyr-d-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP). These results suggest that EM-1 acts at μ-opioid receptors to modulate viscerosensory input and specific components of local synaptic circuitry in the NTS.

3-Mercaptopropionic acid inhibits GABA release from rat brain slices in vitro

1981 ◽  
Vol 229 (2) ◽  
pp. 371-377 ◽  
Author(s):  
S.G. Fan ◽  
M. Wusteman ◽  
L.L. Iversen
Keyword(s):  
Rat Brain ◽  
Brain Slices ◽  
Gaba Release ◽  
Mercaptopropionic Acid
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