1
|
Rajaram E, Pagella S, Grothe B, Kopp-Scheinpflug C. Physiological and anatomical development of glycinergic inhibition in the mouse superior paraolivary nucleus following hearing onset. J Neurophysiol 2020; 124:471-483. [PMID: 32667247 DOI: 10.1152/jn.00053.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Neural circuits require balanced synaptic excitation and inhibition to ensure accurate neural computation. Our knowledge about the development and maturation of inhibitory synaptic inputs is less well developed than that concerning excitation. Here we describe the maturation of an inhibitory circuit within the mammalian auditory brainstem where counterintuitively, inhibition drives action potential firing of principal neurons. With the use of combined anatomical tracing and electrophysiological recordings from mice, neurons of the superior paraolivary nucleus (SPN) are shown to receive converging glycinergic input from at least four neurons of the medial nucleus of the trapezoid body (MNTB). These four axons formed 30.71 ± 2.72 (means ± SE) synaptic boutons onto each SPN neuronal soma, generating a total inhibitory conductance of 80 nS. Such strong inhibition drives the underlying postinhibitory rebound firing mechanism, which is a hallmark of SPN physiology. In contrast to inhibitory projections to the medial and lateral superior olives, the inhibitory projection to the SPN does not exhibit experience-dependent synaptic refinement following the onset of hearing. These findings emphasize that the development and function of neural circuits cannot be inferred from one synaptic target to another, even if both originate from the same neuron.NEW & NOTEWORTHY Neuronal activity regulates development and maturation of neural circuits. This activity can include spontaneous burst firing or firing elicited by sensory input during early development. For example, auditory brainstem circuits involved in sound localization require acoustically evoked activity to form properly. Here we show, that an inhibitory circuit, involved in processing sound offsets, gaps, and rhythmically modulated vocal communication signals, matures before the onset of acoustically evoked activity.
Collapse
Affiliation(s)
- Ezhilarasan Rajaram
- Department of Biology II, Division Neurobiology, Ludwig-Maximilians-University, Munich, Germany.,Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University, Munich, Germany
| | - Sara Pagella
- Department of Biology II, Division Neurobiology, Ludwig-Maximilians-University, Munich, Germany.,Graduate School of Systemic Neurosciences, Ludwig-Maximilians-University, Munich, Germany
| | - Benedikt Grothe
- Department of Biology II, Division Neurobiology, Ludwig-Maximilians-University, Munich, Germany
| | - Conny Kopp-Scheinpflug
- Department of Biology II, Division Neurobiology, Ludwig-Maximilians-University, Munich, Germany
| |
Collapse
|
2
|
Rodrigues AL, Brescia M, Koschinski A, Moreira TH, Cameron RT, Baillie G, Beirão PSL, Zaccolo M, Cruz JS. Increase in Ca 2+ current by sustained cAMP levels enhances proliferation rate in GH3 cells. Life Sci 2017; 192:144-150. [PMID: 29183797 DOI: 10.1016/j.lfs.2017.11.040] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Revised: 11/20/2017] [Accepted: 11/24/2017] [Indexed: 12/12/2022]
Abstract
AIMS Ca2+ and cAMP are important intracellular modulators. In order to generate intracellular signals with various amplitudes, as well as different temporal and spatial properties, a tightly and precise control of these modulators in intracellular compartments is necessary. The aim of this study was to evaluate the effects of elevated and sustained cAMP levels on voltage-dependent Ca2+ currents and proliferation in pituitary tumor GH3 cells. MAIN METHODS Effect of long-term exposure to forskolin and dibutyryl-cyclic AMP (dbcAMP) on Ca2+ current density and cell proliferation rate were determined by using the whole-cell patch-clamp technique and real time cell monitoring system. The cAMP levels were assayed, after exposing transfected GH3 cells with the EPAC-1 cAMP sensor to forskolin and dbcAMP, by FRET analysis. KEY FINDINGS Sustained forskolin treatment (24 and 48h) induced a significant increase in total Ca2+ current density in GH3 cells. Accordingly, dibutyryl-cAMP incubation (dbcAMP) also elicited increase in Ca2+ current density. However, the maximum effect of dbcAMP occurred only after 72h incubation, whereas forskolin showed maximal effect at 48h. FRET-experiments confirmed that the time-course to elevate intracellular cAMP was distinct between forskolin and dbcAMP. Mibefradil inhibited the fast inactivating current component selectively, indicating the recruitment of T-type Ca2+ channels. A significant increase on cell proliferation rate, which could be related to the elevated and sustained intracellular levels of cAMP was observed. SIGNIFICANCE We conclude that maintaining high levels of intracellular cAMP will cause an increase in Ca2+ current density and this phenomenon impacts proliferation rate in GH3 cells.
Collapse
Affiliation(s)
- Andréia Laura Rodrigues
- Laboratório CaCIA, Faculdade de Ciências Humanas Sociais e da Saúde, Universidade FUMEC, Brazil.
| | - Marcella Brescia
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, UK
| | - Andreas Koschinski
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, UK
| | - Thaís Helena Moreira
- Laboratório de Membranas Excitáveis e de Biologia Cardiovascular, Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Ryan T Cameron
- Institute of Cardiovascular and Medical Sciences, Glasgow University, Glasgow, UK
| | - George Baillie
- Institute of Cardiovascular and Medical Sciences, Glasgow University, Glasgow, UK
| | - Paulo S L Beirão
- Laboratório de Membranas Excitáveis e de Biologia Cardiovascular, Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, UK
| | - Jader S Cruz
- Laboratório de Membranas Excitáveis e de Biologia Cardiovascular, Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
| |
Collapse
|
3
|
Insulin-mediated upregulation of T-type Ca2+ currents in GH3 cells is mediated by increased endosomal recycling and incorporation of surface membrane Cav3.1 channels. Cell Calcium 2012; 52:377-87. [DOI: 10.1016/j.ceca.2012.06.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 05/15/2012] [Accepted: 06/13/2012] [Indexed: 11/20/2022]
|
4
|
Stojilkovic SS, Kretschmannova K, Tomić M, Stratakis CA. Dependence of the excitability of pituitary cells on cyclic nucleotides. J Neuroendocrinol 2012; 24:1183-200. [PMID: 22564128 PMCID: PMC3421050 DOI: 10.1111/j.1365-2826.2012.02335.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Cyclic 3',5'-adenosine monophosphate and cyclic 3',5'-guanosine monophosphate are intracellular (second) messengers that are produced from the nucleotide triphosphates by a family of enzymes consisting of adenylyl and guanylyl cyclases. These enzymes are involved in a broad array of signal transduction pathways mediated by the cyclic nucleotide monophosphates and their kinases, which control multiple aspects of cell function through the phosphorylation of protein substrates. We review the findings and working hypotheses on the role of the cyclic nucleotides and their kinases in the control of electrical activity of the endocrine pituitary cells and the plasma membrane channels involved in this process.
Collapse
Affiliation(s)
- S S Stojilkovic
- Sections on Cellular Signalling and Endocrinology and Genetics, The Eunice Kennedy Shiver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | | | | | | |
Collapse
|
5
|
Lopez-Charcas O, Rivera M, Gomora JC. Block of Human CaV3 Channels by the Diuretic Amiloride. Mol Pharmacol 2012; 82:658-67. [DOI: 10.1124/mol.112.078923] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
6
|
Abstract
Endocrine pituitary cells are neuronlike; they express numerous voltage-gated sodium, calcium, potassium, and chloride channels and fire action potentials spontaneously, accompanied by a rise in intracellular calcium. In some cells, spontaneous electrical activity is sufficient to drive the intracellular calcium concentration above the threshold for stimulus-secretion and stimulus-transcription coupling. In others, the function of these action potentials is to maintain the cells in a responsive state with cytosolic calcium near, but below, the threshold level. Some pituitary cells also express gap junction channels, which could be used for intercellular Ca(2+) signaling in these cells. Endocrine cells also express extracellular ligand-gated ion channels, and their activation by hypothalamic and intrapituitary hormones leads to amplification of the pacemaking activity and facilitation of calcium influx and hormone release. These cells also express numerous G protein-coupled receptors, which can stimulate or silence electrical activity and action potential-dependent calcium influx and hormone release. Other members of this receptor family can activate calcium channels in the endoplasmic reticulum, leading to a cell type-specific modulation of electrical activity. This review summarizes recent findings in this field and our current understanding of the complex relationship between voltage-gated ion channels, ligand-gated ion channels, gap junction channels, and G protein-coupled receptors in pituitary cells.
Collapse
Affiliation(s)
- Stanko S Stojilkovic
- Program in Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Building 49, Room 6A-36, 49 Convent Drive, Bethesda, Maryland 20892-4510, USA.
| | | | | |
Collapse
|
7
|
Avila T, Hernández-Hernández O, Almanza A, de León MB, Urban M, Soto E, Cisneros B, Felix R. Regulation of Ca v 3.1 channels by glucocorticoids. Cell Mol Neurobiol 2010; 29:1265-73. [PMID: 19533336 DOI: 10.1007/s10571-009-9422-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Accepted: 06/01/2009] [Indexed: 12/13/2022]
Abstract
The activity of low voltage-activated Ca(2+) (Ca(V)3) channels is tightly coupled to neurotransmitter and hormone secretion. Previous studies have shown that Ca(V)3 channels are regulated by glucocorticoids (GCs), though the mechanism underlying channel regulation remains unclear. Here, using the pituitary GH(3) cell line as a model, we investigated whether Ca(V)3 channel expression is under the control of GCs, and if their actions are mediated by transcriptional and/or post-transcriptional mechanisms. RT-PCR and western blot analyses showed that Ca(V)3.1 but not Ca(V)3.2 and Ca(V)3.3 channels is expressed in the GH(3) cells, and patch clamp recordings confirmed that Ca(2+) currents through low voltage-activated channels were decreased after chronic treatment with GCs. Consistent with this, total plasma membrane expression of Ca(V)3.1 protein as analyzed by cell-surface biotinylation assays and semi-quantitative western blotting was also down-regulated, while quantitative real-time RT-PCR analysis revealed a significant decrease of Ca(V)3.1 mRNA expression in the treated cells. In contrast, patch-clamp recordings on HEK-293 cells stably expressing recombinant Ca(V)3.1 channels showed that Ca(2+) currents were not affected by GC treatment. These results suggest that decreased transcription is a likely mechanism to explain the inhibitory actions of GCs on the functional expression of native Ca(V)3.1 channels.
Collapse
Affiliation(s)
- Traudy Avila
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies of the National Polytechnic Institute, Cinvestav-IPN, Mexico City, Mexico
| | | | | | | | | | | | | | | |
Collapse
|
8
|
López-Domínguez AM, Espinosa JL, Navarrete A, Avila G, Cota G. Nerve growth factor affects Ca2+ currents via the p75 receptor to enhance prolactin mRNA levels in GH3 rat pituitary cells. J Physiol 2006; 574:349-65. [PMID: 16690703 PMCID: PMC1817754 DOI: 10.1113/jphysiol.2006.110791] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In clonal pituitary GH(3) cells, spontaneous action potentials drive the opening of Ca(v)1 (L-type) channels, leading to Ca(2+) transients that are coupled to prolactin gene transcription. Nerve growth factor (NGF) has been shown to stimulate prolactin synthesis by GH(3) cells, but the underlying mechanisms are unknown. Here we studied whether NGF influences prolactin gene expression and Ca(2+) currents. By using RT-PCR, NGF (50 ng ml(-1)) was found to augment prolactin mRNA levels by approximately 80% when applied to GH(3) cells for 3 days. A parallel change in the prolactin content was detected by Western blotting. Both NGF-induced responses were mimicked by an agonist (Bay K 8644) and prevented by a blocker (nimodipine) of L-type channels. In whole-cell patch-clamp experiments, NGF enhanced the L-type Ca(2+) current by approximately 2-fold within 60 min. This effect reversed quickly upon growth factor withdrawal, but was maintained for days in the continued presence of NGF. In addition, chronic treatment (>or= 24 h) with NGF amplified the T-type current, which flows through Ca(v)3 channels and is thought to support pacemaking activity. Thus, NGF probably increases the amount of Ca(2+) that enters per action potential and may also induce a late increase in spike frequency. MC192, a specific antibody for the p75 neurotrophin receptor, but not tyrosine kinase inhibitors (K252a and lavendustin A), blocked the effects of NGF on Ca(2+) currents. Overall, the results indicate that NGF activates the p75 receptor to cause a prolonged increase in Ca(2+) influx through L-type channels, which in turn up-regulates the prolactin mRNA.
Collapse
Affiliation(s)
- Adriana M López-Domínguez
- Department of Physiology, Biophysics and Neurosciences, Cinvestav-IPN, AP 14-740, Mexico, DF 07000, Mexico
| | | | | | | | | |
Collapse
|