1
|
Maeda S, Minato Y, Kuwahara-Otani S, Yamanaka H, Maeda M, Kataoka Y, Yagi H. Morphology of Schwann Cell Processes Supports Renal Sympathetic Nerve Terminals With Local Distribution of Adrenoceptors. J Histochem Cytochem 2022; 70:495-513. [PMID: 35708491 DOI: 10.1369/00221554221106812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nerves in the renal parenchyma comprise sympathetic nerves that act on renal arteries and tubules to decrease blood flow and increase primary urine reabsorption, respectively. Synaptic vesicles release neurotransmitters that activate their effector tissues. However, the mechanisms by which neurotransmitters exert individual responses to renal effector cells remain unknown. Here, we investigated the spatial and molecular compositional associations of renal Schwann cells (SC) supporting the nerve terminals in male rats. The nerve terminals of vascular smooth muscle cells (SMCs) enclosed by renal SC processes were exposed through windows facing the effectors with presynaptic specializations. We found that the adrenergic receptors (ARs) α2A, α2C, and β2 were localized in the SMC and the basal side of the tubules, where the nerve terminals were attached, whereas the other subtypes of ARs were distributed in the glomerular and luminal side, where the norepinephrine released from nerve endings may have indirect access to ARs. In addition, integrins α4 and β1 were coexpressed in the nerve terminals. Thus, renal nerve terminals could contact their effectors via integrins and may have a structure, covered by SC processes, suitable for intensive and directional release of neurotransmitters into the blood, rather than specialized structures in the postsynaptic region.
Collapse
Affiliation(s)
| | | | | | - Hiroki Yamanaka
- Department of Anatomy and Cell Biology.,Department of Anatomy and Neuroscience
| | - Mitsuyo Maeda
- Hyogo College of Medicine, Nishinomiya, Japan; Multi-Modal Microstructure Analysis Unit, RIKEN-JEOL Collaboration Center, RIKEN, Hyogo, Japan.,Laboratory for Cellular Function Imaging, RIKEN Center for Biosystems Dynamics Research, RIKEN, Hyogo, Japan
| | - Yosky Kataoka
- Hyogo College of Medicine, Nishinomiya, Japan; Multi-Modal Microstructure Analysis Unit, RIKEN-JEOL Collaboration Center, RIKEN, Hyogo, Japan.,Laboratory for Cellular Function Imaging, RIKEN Center for Biosystems Dynamics Research, RIKEN, Hyogo, Japan
| | | |
Collapse
|
2
|
Gabella G. Muscle cells, nerves, fibroblasts and vessels in the detrusor of the rat urinary bladder. J Smooth Muscle Res 2020; 55:34-67. [PMID: 31708509 PMCID: PMC6851244 DOI: 10.1540/jsmr.55.34] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
All the cells of rat detrusor muscle fall into one of five ultrastructural types: muscle
cells, fibroblasts, axons and glia, and vascular cells (endothelial cells and pericytes).
The tissue is ~79% cellular and 21% non-cellular. Muscle cells occupy 72%, nerves ~4% (1/3
axons, 2/3 glia), and fibroblast >3% of space. Muscle cells (up to 6 µm across and ~600
µm long, packed to almost 100,000 per mm2) have surface-to-volume ratio of 2.4
µm2/µm3 ~93% of cell volume is contractile apparatus, 3.1%
mitochondria and 2.5% nucleus. Cell profiles are irregular but sectional area decreases
regularly towards either end of the cell. Muscle cells are gathered into bundles (the
mechanical units of detrusor), variable in length and size, but of constant width. The
musculature is highly compact (without fascia or capsule) with smooth outer surfaces and
extensive association and adhesion between its cells. Among many types of intercellular
contact and junction, digitations are very common, each muscle cell issuing minute
finger-like processes that abut on adjacent cells. Sealed apposition are wide areas of
specialized contact, possibly forming a chamber between two muscle cells, distinct from
the extracellular space at large (stromal space). The innervation is very dense, virtually
all intramuscular axons being varicose (including afferent ones). There are identifiable
neuro-muscular junctions on each muscle cell, often several junctions on a single cell.
There are also unattached terminals. Fibroblasts (involved in the production of collagen),
~1% of the total number of cells, do not make specialized contacts.
Collapse
|
3
|
Gabella G. Afferent nerve fibres in the wall of the rat urinary bladder. Cell Tissue Res 2018; 376:25-35. [DOI: 10.1007/s00441-018-2965-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 11/12/2018] [Indexed: 01/28/2023]
|
4
|
DeLalio LJ, Keller AS, Chen J, Boyce AK, Artamonov M, Askew-Page HR, Keller TS, Johnstone SR, Weaver RB, Good ME, Murphy S, Best AK, Mintz EL, Penuela S, Greenwood I, Machado RF, Somlyo AV, Swayne LA, Minshall R, Isakson BE. Interaction Between Pannexin 1 and Caveolin-1 in Smooth Muscle Can Regulate Blood Pressure. Arterioscler Thromb Vasc Biol 2018; 38:2065-2078. [PMID: 30026274 PMCID: PMC6202122 DOI: 10.1161/atvbaha.118.311290] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Accepted: 06/19/2018] [Indexed: 12/31/2022]
Abstract
Objective- Sympathetic nerve innervation of vascular smooth muscle cells (VSMCs) is a major regulator of arteriolar vasoconstriction, vascular resistance, and blood pressure. Importantly, α-adrenergic receptor stimulation, which uniquely couples with Panx1 (pannexin 1) channel-mediated ATP release in resistance arteries, also requires localization to membrane caveolae. Here, we test whether localization of Panx1 to Cav1 (caveolin-1) promotes channel function (stimulus-dependent ATP release and adrenergic vasoconstriction) and is important for blood pressure homeostasis. Approach and Results- We use in vitro VSMC culture models, ex vivo resistance arteries, and a novel inducible VSMC-specific Cav1 knockout mouse to probe interactions between Panx1 and Cav1. We report that Panx1 and Cav1 colocalized on the VSMC plasma membrane of resistance arteries near sympathetic nerves in an adrenergic stimulus-dependent manner. Genetic deletion of Cav1 significantly blunts adrenergic-stimulated ATP release and vasoconstriction, with no direct influence on endothelium-dependent vasodilation or cardiac function. A significant reduction in mean arterial pressure (total=4 mm Hg; night=7 mm Hg) occurred in mice deficient for VSMC Cav1. These animals were resistant to further blood pressure lowering using a Panx1 peptide inhibitor Px1IL2P, which targets an intracellular loop region necessary for channel function. Conclusions- Translocalization of Panx1 to Cav1-enriched caveolae in VSMCs augments the release of purinergic stimuli necessary for proper adrenergic-mediated vasoconstriction and blood pressure homeostasis.
Collapse
Affiliation(s)
- Leon J. DeLalio
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA
| | - Alexander S. Keller
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA
| | - Jiwang Chen
- Department of Medicine, The University of Illinois at Chicago, Chicago, IL
| | - Andrew K.J. Boyce
- Division of Medical Sciences, Centre for Biomedical Research, University of Victoria, Victoria, BC Canada
| | - Mykhaylo Artamonov
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA
| | - Henry R. Askew-Page
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
| | - T.C. Stevenson Keller
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA
| | - Scott R. Johnstone
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
| | - Rachel B. Weaver
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
| | - Miranda E. Good
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
| | - Sara Murphy
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
| | - Angela K. Best
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
| | - Ellen L. Mintz
- Department of Biomedical Engineering, University of Virginia School of Engineering, Charlottesville, VA
| | - Silvia Penuela
- Department of Anatomy and Cell Biology, Schulich Scholl of Medicine and Dentistry, University of Western Ontario, London ON, Canada
| | - Iain Greenwood
- Molecular and Clinical Sciences Research Institute, St. George’s University London UK
| | - Roberto F. Machado
- Division of Pulmonary, Critical Care, Sleep, & Occupational Medicine, Indiana University School of Medicine, Indianapolis, IN
| | - Avril V. Somlyo
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA
| | - Leigh Anne Swayne
- Division of Medical Sciences, Centre for Biomedical Research, University of Victoria, Victoria, BC Canada
| | - Richard Minshall
- Department of Pharmacology and Department of Anesthesiology, The University of Illinois at Chicago, Chicago, IL
| | - Brant E. Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA
- Department of Molecular Physiology and Biophysics, University of Virginia, Charlottesville, VA
| |
Collapse
|
5
|
Slater CR. The functional organization of motor nerve terminals. Prog Neurobiol 2015; 134:55-103. [DOI: 10.1016/j.pneurobio.2015.09.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 08/28/2015] [Accepted: 09/05/2015] [Indexed: 12/19/2022]
|
6
|
Bayguinov PO, Hennig GW, Smith TK. Ca2+ imaging of activity in ICC-MY during local mucosal reflexes and the colonic migrating motor complex in the murine large intestine. J Physiol 2010; 588:4453-74. [PMID: 20876203 DOI: 10.1113/jphysiol.2010.196824] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Colonic migrating motor complexes (CMMCs) are neurally mediated, cyclical contractile and electrical events, which typically propagate along the colon every 2-3 min in the mouse. We examined the interactions between myenteric neurons, interstitial cells of Cajal in the myenteric region (ICC-MY) and smooth muscle cells during CMMCs using Ca(2+) imaging. CMMCs occurred spontaneously or were evoked by stimulating the mucosa locally, or by brushing it at either end of the colon. Between CMMCs, most ICC-MY were often quiescent; their lack of activity was correlated with ongoing Ca(2+) transients in varicosities on the axons of presumably inhibitory motor neurons that were on or surrounded ICC-MY. Ca(2+) transients in other varicosities initiated intracellular Ca(2+) waves in adjacent ICC-MY, which were blocked by atropine, suggesting they were on the axons of excitatory motor neurons. Following TTX (1 μM), or blockade of inhibitory neurotransmission with N(ω)-nitro-L-arginine (L-NA, a NO synthesis inhibitor, 10 μM) and MRS 2500 (a P2Y(1) antagonist, 1 μM), ongoing spark/puff like activity and rhythmic intracellular Ca(2+) waves (38.1 ± 2.9 cycles min(-1)) were observed, yet this activity was uncoupled, even between ICC-MY in close apposition. During spontaneous or evoked CMMCs there was an increase in the frequency (62.9 ± 1.4 cycles min(-1)) and amplitude of Ca(2+) transients in ICC-MY and muscle, which often had synchronized activity. At the same time, activity in varicosites along excitatory and inhibitory motor nerve fibres increased and decreased respectively, leading to an overall excitation of ICC-MY. Atropine (1 μM) reduced the evoked responses in ICC-MY, and subsequent addition of an NK1 antagonist (RP 67580, 500 nM) completely blocked the responses to stimulation, as did applying these drugs in reverse order. An NKII antagonist (MEN 10,376, 500 nM) had no effect on the evoked responses in ICC-MY. Following TTX application, carbachol (1 μM), substance P (1 μM) and an NKI agonist (GR73632, 100 nM) produced the fast oscillations superimposed on a slow increase in Ca(2+) in ICC-MY, whereas SNP (an NO donor, 10 μM) abolished all activity in ICC-MY. In conclusion, ICC-MY, which are under tonic inhibition, are pacemakers whose activity can be synchronized by excitatory nerves to couple the longitudinal and circular muscles during the CMMC. ICC-MY receive excitatory input from motor neurons that release acetylcholine and tachykinins acting on muscarinic and NK1 receptors, respectively.
Collapse
Affiliation(s)
- Peter O Bayguinov
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | | | | |
Collapse
|
7
|
Ren J, Zhou X, Galligan JJ. 5-HT4 receptor activation facilitates recovery from synaptic rundown and increases transmitter release from single varicosities of myenteric neurons. Am J Physiol Gastrointest Liver Physiol 2008; 294:G1376-83. [PMID: 18436623 PMCID: PMC4254768 DOI: 10.1152/ajpgi.00078.2008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
5-HT(4) receptor agonists facilitate synaptic transmission in the enteric nervous system, and these drugs are used to treat constipation. In the present study, we investigated the effects of the 5-HT(4) receptor agonist, renzapride, on rundown and recovery of fast excitatory postsynaptic potentials (fEPSPs) during and after trains of stimulation and on transmitter release from individual myenteric neuronal varicosities. Intracellular electrophysiological methods were used to record fEPSPs from neurons in longitudinal muscle myenteric plexus preparations of guinea pig ileum in vitro. During trains of supramaximal electrical stimulation (10 Hz, 2 s), fEPSP amplitude declined (time constant = 0.6 +/- 0.1 s) from 17 +/- 2 mV to 0.7 +/- 0.3 mV. Renzapride (0.1 microM) did not change the time constant for fEPSP rundown, but it decreased the time constant for recovery of fEPSP amplitude after the stimulus train from 7 +/- 2 s to 1.6 +/- 0.2 s (P < 0.05). 5-HT (0.1 microM) also increased fEPSPs and facilitated recovery from rundown. The adenylate cyclase activator, forskolin (1 muM), mimicked the actions of renzapride and 5-HT, whereas H-89, a protein kinase A (PKA) inhibitor, blocked the effects of renzapride. We used nicotinic acetylcholine receptor containing outside-out patches obtained from myenteric neurons maintained in primary culture to detect acetylcholine release from single varicosities. Renzapride (0.1 microM) increased release probability twofold. We conclude that 5-HT(4) receptors activate the adenylyl cyclase-PKA pathway to increase acetylcholine release from single varicosities and to accelerate recovery from synaptic rundown. These responses may contribute to the prokinetic actions of 5-HT(4) receptor agonists.
Collapse
Affiliation(s)
- Jianhua Ren
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
| | - Xiaoping Zhou
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824, USA
| | - James J Galligan
- Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA,Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824, USA
| |
Collapse
|
8
|
Hanani M, Nissan A, Freund HR. Innervation of submucosal adipocytes in the human colon. Neurosci Lett 2007; 428:7-10. [DOI: 10.1016/j.neulet.2007.09.038] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2007] [Revised: 09/16/2007] [Accepted: 09/18/2007] [Indexed: 12/23/2022]
|
9
|
Juranek J, Mukherjee K, Rickmann M, Martens H, Calka J, Südhof TC, Jahn R. Differential expression of active zone proteins in neuromuscular junctions suggests functional diversification. Eur J Neurosci 2007; 24:3043-52. [PMID: 17156365 DOI: 10.1111/j.1460-9568.2006.05183.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Nerve terminals of the central nervous system (CNS) contain specialized release sites for synaptic vesicles, referred to as active zones. They are characterized by electron-dense structures that are tightly associated with the presynaptic plasma membrane and organize vesicle docking and priming sites. Recently, major protein constituents of active zones have been identified, including the proteins Piccolo, Bassoon, RIM, Munc13, ERCs/ELKs/CASTs and liprins. While it is becoming apparent that each of these proteins is essential for synaptic function in the CNS, it is not known to what extent these proteins are involved in synaptic function of the peripheral nervous system. Somatic neuromuscular junctions contain morphologically and functionally defined active zones with similarities to CNS synapses. In contrast, sympathetic neuromuscular varicosities lack active zone-like morphological specializations. Using immunocytochemistry at the light and electron microscopic level we have now performed a systematic investigation of all five major classes of active zone proteins in peripheral neuromuscular junctions. Our results show that somatic neuromuscular endplates contain a full complement of all active zone proteins. In contrast, varicosities of the vas deferens contain a subset of active zone proteins including Bassoon and ELKS2, with the other four components being absent. We conclude that Bassoon and ELKS2 perform independent and specialized functions in synaptic transmission of autonomic synapses.
Collapse
Affiliation(s)
- Judyta Juranek
- Department of Neurobiology, MPI for Biophysical Chemistry, 37077 Göttingen/Germany
| | | | | | | | | | | | | |
Collapse
|
10
|
Tompkins JD, Parsons RL. Exocytotic release of ATP and activation of P2X receptors in dissociated guinea pig stellate neurons. Am J Physiol Cell Physiol 2006; 291:C1062-71. [PMID: 16760262 DOI: 10.1152/ajpcell.00472.2005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Activation of P2X receptors by a Ca(2+)- and soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein-dependent release of ATP was measured using patch-clamp recordings from dissociated guinea pig stellate neurons. Asynchronous transient inward currents (ASTICs) were activated by depolarization or treatment with the Ca(2+) ionophore ionomycin (1.5 and 3 microM). During superfusion with a HEPES-buffered salt solution containing 2.5 mM Ca(2+), depolarizing voltage steps (-60 to 0 mV, 500 ms) evoked ASTICs on the decaying phase of a larger, transient inward current. Equimolar substitution of Ba(2+) for Ca(2+) augmented the postdepolarization frequency of ASTICs, while eliminating the larger transient current. Perfusion with an ionomycin-containing solution elicited a sustained activation of ASTICs, allowing quantitative analysis over a range of holding potentials. Under these conditions, increasing extracellular [Ca(2+)] to 5 mM increased ASTIC frequency, whereas no events were observed following replacement of Ca(2+) with Mg(2+), demonstrating a Ca(2+) requirement. ASTICs were Na(+) dependent, inwardly rectifying, and reversed near 0 mV. Treatment with the nonselective purinergic receptor antagonist pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) (10 microM) blocked all events under both conditions, whereas the ganglionic nicotinic antagonist hexamethonium (100 microM and 1 mM) had no effect. PPADS also blocked the macroscopic inward current evoked by exogenously applied ATP (300 microM). The presence of botulinum neurotoxin E (BoNT/E) in the whole-cell recording electrode significantly attenuated the ionomycin-induced ASTIC activity, whereas phorbol ester treatment potentiated this activity. These results suggest that ASTICs are mediated by vesicular release of ATP and activation of P2X receptors.
Collapse
Affiliation(s)
- John D Tompkins
- University of Vermont, College of Medicine, Dept. of Anatomy and Neurobiology, Burlington, VT 05405, USA.
| | | |
Collapse
|
11
|
Palani D, Manchanda R. Effects of Heptanol on Neurogenic Contractions of Vas Deferens: A Comparative Study of Stimulation Frequency in Guinea Pig and Rat. J Physiol Sci 2006; 56:21-8. [PMID: 16779910 DOI: 10.2170/physiolsci.rp001205] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
This study examines the role of gap junctional communication in smooth muscle in relation to the frequency of stimulation and the innervation density of the tissue in the generation of neurogenic contractions. Toward this end the effects of heptanol, a gap junctional blocker, on the neurogenic contractions of guinea pig and rat vas deferens at different frequencies of stimulation (single pulse, 5, 10, 20, 40, 60, and 80 Hz) were studied. In both the prostatic and epididymal halves of these tissues, heptanol abolished the neurogenic contractions at the lower frequencies of stimulation. At higher frequencies, contractions were resistant to heptanol action. The effect of heptanol on the neurogenic contractions was found to decrease with increasing stimulation frequency. The neurogenic contractions of rat vas deferens were more resistant to heptanol than those of guinea pig vas deferens. Our data indicate that gap junctional communication is significant in the generation of neurogenic contractions in both guinea pig and rat vas deferens in a frequency-dependent manner, and we discuss the mechanisms underlying these findings.
Collapse
Affiliation(s)
- D Palani
- Biomedical Engineering Group, School of Bioscience and Bioengineering, Indian Institute of Technology-Bombay, Mumbai, 400076, India
| | | |
Collapse
|
12
|
Bennet MR, Gibson WG, Lemon G. Neuronal cell death, nerve growth factor and neurotrophic models: 50 years on. Auton Neurosci 2002; 95:1-23. [PMID: 11871773 DOI: 10.1016/s1566-0702(01)00358-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Viktor Hamburger has just died at the age of 100. It is 50 years since he and Rita Levi-Montalcini laid the foundations for the study of naturally occurring cell death and of neurotrophic factors in the nervous system. In a period of less than 10 years, from 1949 to 1958, Hamburger and Levi-Montalcini made the following seminal discoveries: that neuron cell death occurs in dorsal root ganglia, sympathetic ganglia and the cervical column of motoneurons; that the predictions arising from this observation, namely that survival is dependent on the supply of a trophic factor, could be substantiated by studying the effects of a sarcoma on the proliferation of ganglionic processes both in vivo and in vitro; and that the proliferation of these processes could be used as an assay system to isolate the factor. This work provides a short review mostly of the early history of this subject in the context of the Hamburger/Levi-Montalcini paradigm. This acts as an introduction to a consideration of models that have been proposed to account for how the different sources of growth factors provide for the survival of neurons during development. It is suggested that what has been called the 'social-control' model provides the most parsimonious quantitative description of the contribution of trophic factors to neuronal survival, a concept for which we are in debt to Viktor Hamburger and Rita Levi-Montalcini.
Collapse
Affiliation(s)
- M R Bennet
- Department of Physiology, Institute for Biomedical Research, University of Sydney, New South Wales, Australia.
| | | | | |
Collapse
|
13
|
Bennett MR, Farnell L, Gibson WG, Lin YQ, Blair DH. Quantal and non-quantal current and potential fields around individual sympathetic varicosities on release of ATP. Biophys J 2001; 80:1311-28. [PMID: 11222293 PMCID: PMC1301324 DOI: 10.1016/s0006-3495(01)76105-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The electrical phenomena that occur at sympathetic varicosities due to the release of ATP include spontaneous and evoked excitatory junction potentials (SEJPs and EJPs; recorded with an intracellular electrode) as well as fast and slow excitatory junctional currents (EJCs; recorded with a loose-patch electrode placed over varicosities). The electrical analysis of these transients is hampered by lack of a detailed theory describing how current and potential fields are generated upon the release of a quantum of ATP. Here, we supply such a theory and develop a computational model for the electrical properties of a smooth muscle syncytium placed within a volume conductor, using a distributed representation for the individual muscle cells. The amplitudes and temporal characteristics of both SEJPs and fast EJCs are predicted by the theory, but those of the slow EJCs are not. It is shown that these slow components cannot arise as a consequence of propagation of fast quantal components from their site of origin in the muscle syncytium to the point of recording. The possibility that slow components arise by a mechanism of transmitter secretion that is different from quantal release is examined. Experiments that involve inserting peptide fragments of soluble N-ethylmaleimide-sensitive fusion attachment protein (alpha-SNAP) into varicosities, a procedure that is known to block quantal release, left the slow component of release unaffected. This work provides an internally consistent description of quantal potential and current fields about the varicosities of sympathetic nerve terminals and provides evidence for a non-quantal form of transmitter release.
Collapse
Affiliation(s)
- M R Bennett
- The Neurobiology Laboratory, Institute for Biomedical Research, and Department of Physiology, Sydney, New South Wales 2006, Australia.
| | | | | | | | | |
Collapse
|
14
|
Stjärne L. Novel dual 'small' vesicle model of ATP- and noradrenaline-mediated sympathetic neuromuscular transmission. Auton Neurosci 2001; 87:16-36. [PMID: 11270138 DOI: 10.1016/s1566-0702(00)00246-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The main question asked was if sympathetic nerves in guinea-pig vas deferens release the co-transmitters ATP and noradrenaline from the same, or different vesicles, i.e. in fixed combinations or independently. The extracellularly recorded excitatory junction current (EJC) and the fractional increase in overflow of tritium (delta T) were used to monitor the per pulse secretion of ATP and [3H]NA, respectively, during electrical stimulation with 1-3000 pulses at 0.1-40 Hz. The frequency- and train length-dependence and alpha 2-adrenoceptor-mediated autoinhibition of these parameters, and of the ATP-mediated twitch contraction, were compared first in the presence of cocaine (to block noradrenaline reuptake), then after brief exposure to phenoxybenzamine (PBA, to irreversibly 'destroy' alpha 2-autoreceptors). Parallel variations of EJC/p(ulse) and delta T/p(ulse) under all conditions would support, non-parallel variations argue against exocytosis of ATP and noradrenaline from the same vesicles. The main findings were that facilitation and alpha 2-autoinhibition of EJC/p and delta T/p were remarkably similar during stimulation at 2 Hz but increasingly dissimilar at higher frequencies. delta T/p remained strongly facilitated and tightly controlled by activation of alpha 2-autoreceptors at 10-40 Hz, but both the facilitation and the sensitivity to alpha 2-autoinhibition of EJC/p were inversely related to frequency. At 40 Hz EJCs were 'small', minimally facilitated and totally unaffected by cocaine or PBA, i.e. insensitive to alpha 2-autoinhibition. Nevertheless, activation of alpha 2-receptors during the 40 Hz train strongly restricted the 'post-tetanic augmentation' (PTA) of the first EJC 10 s after the tetanus. Comparison between the frequency dependence of EJCs and the twitch contraction in the presence of cocaine or after PBA treatment indicates that it is the 'summed EJC per second', i.e. the ATP-driven current injection per unit time into smooth muscle, which triggers the twitch. The working hypothesis is proposed that these nerves use two classes of 'small vesicles' (SVs) to store and release either 'big' or 'small' ATP and noradrenaline 'quanta', and that differences in properties (Ca2+ affinity, capacity) of Ca2+ receptors in the SV membranes enable the nerves to selectively secrete 'big quanta' at low frequency and 'small quanta' during trains at high frequency.
Collapse
Affiliation(s)
- L Stjärne
- Department of Physiology and Pharmacology, Karolinska Institutet, S-17177 Stockholm, Sweden.
| |
Collapse
|
15
|
Surprenant A, Schneider DA, Wilson HL, Galligan JJ, North RA. Functional properties of heteromeric P2X(1/5) receptors expressed in HEK cells and excitatory junction potentials in guinea-pig submucosal arterioles. JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 2000; 81:249-63. [PMID: 10869729 DOI: 10.1016/s0165-1838(00)00123-5] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
P2X receptors are ATP-gated cation channels; they form as homomers or heteromers from a family of seven related subunits. In particular, heteromeric channels comprising P2X(2) and P2X(3) subunits, or P2X(1) and P2X(5) subunits, show distinctive physiological and pharmacological properties in heterologous expression systems. There is substantial evidence that one of the native P2X receptors in sensory neurones corresponds to the P2X(2/3) heteromer, but there is no evidence for P2X(1/5) heteromers in native tissue. We recorded currents in response to activation of heteromeric P2X(1/5) receptors expressed in HEK293 cells to characterize further their functional properties. The ATP concentration-response curve had a threshold concentration of 1 nM, and a Hill slope of one. TNP-ATP was a weak partial agonist, and a non-competitive antagonist which inhibited maximal ATP currents by 60%. Increasing or decreasing pH from 7.3 shifted the ATP concentration-response curves to the right by fivefold and decreased the maximum current by 40%. Calcium permeability was lower than that observed for other P2X receptors (P(Ca)/P(Na) ratio=1.1). The nanomolar sensitivity of this receptor revealed a steady release of ATP from HEK293 cells, providing an extracellular concentration which ranged from 3 to 300 nM. Noradrenaline (0.3-30 microM) increased ATP-evoked currents by 35%; this facilitation occurred within 20 ms. We also recorded excitatory junction potentials (EJPs) from guinea-pig submucosal arterioles. EJPs were inhibited by suramin and PPADS (IC(50)s of 0.2 microM and 20 microM) but TNP-ATP (0.1-10 microM) inhibited EJPs by <30%. Noradrenaline (0.3-30 microM in the presence of phentolamine and propranolol) decreased EJPs in control preparations but facilitated EJPs by 5-20% in submucosal arterioles from reserpinized guinea-pigs. These properties are discussed in relation to P2X receptors underlying EJPs at autonomic neuroeffector junctions.
Collapse
Affiliation(s)
- A Surprenant
- Institute of Molecular Physiology, University of Sheffield, Alfred Denny Building Western Bank, S10 2TN, Sheffield, UK.
| | | | | | | | | |
Collapse
|
16
|
Stjärne L. Do sympathetic nerves release noradrenaline in "quanta"? JOURNAL OF THE AUTONOMIC NERVOUS SYSTEM 2000; 81:236-43. [PMID: 10869727 DOI: 10.1016/s0165-1838(00)00119-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The discovery of excitatory junction potentials (EJPs) in guinea-pig vas deferens by Burnstock and Holman (1960) showed for the first time that a sympathetic transmitter, now known to be ATP, is secreted in "quanta". As it was assumed at the time that EJPS are triggered by noradrenaline, this discovery led to attempts to use the fractional overflow of noradrenaline from sympathetically innervated tissues to assess, indirectly, the number of noradrenaline molecules in the average "quantum". The basic finding was that each pulse released 1/50000 of the tissue content of noradrenaline, when reuptake was blocked and prejunctional alpha(2)-adrenoceptors were intact. This provided the constraints, two extreme alternatives: (i) each pulse releases 0.2-3% of the content of a vesicle from all varicosities, or (ii) each pulse releases the whole content of a vesicle from 0.2 to 3% of the varicosities. New techniques have made it possible to address questions about the release probability in individual sites, or the "quantal" size, more directly. Results by optical (comparison of the labelling of SV2 and synaptotagmin, proteins in the membrane of transmitter vesicles), electrophysiological (excitatory junction currents, EJCs, at single visualized varicosities) and amperometric (the noradrenaline oxidation current at a carbon fibre electrode) methods reveal that transmitter exocytosis in varicosities is intermittent. The EJC and noradrenaline oxidation current responses (in rat arteries) to a train of single pulses were observed to be similar in intermittency and amplitude fluctuation. This suggests that they are caused by exocytosis of single or very few "quanta" of ATP and noradrenaline, respectively, equal to the contents of single vesicles, from a small population of release sites. These findings support, but do not conclusively prove the validity of the "intermittent" model of noradrenaline release. The question if noradrenaline is always secreted in packets of preset size ("quanta") and if the "quantum" is a subfraction or the whole content of single synaptic vesicles, still remains open.
Collapse
Affiliation(s)
- L Stjärne
- Department of Physiology and Pharmacology, Karolinska Institutet, S-17177, Stockholm, Sweden.
| |
Collapse
|
17
|
Blottner D. Nitric oxide and target-organ control in the autonomic nervous system: Anatomical distribution, spatiotemporal signaling, and neuroeffector maintenance. J Neurosci Res 1999. [DOI: 10.1002/(sici)1097-4547(19991001)58:1<139::aid-jnr14>3.0.co;2-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
18
|
Norlin T, Hilliges M, Brodin L. Immunohistochemical demonstration of exocytosis-regulating proteins within rat molar dentinal tubules. Arch Oral Biol 1999; 44:223-31. [PMID: 10217513 DOI: 10.1016/s0003-9969(98)00115-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
No morphologically defined synaptic structures have so far been detected between nerve terminals and the dentine-producing odontoblasts. Recent studies of the molecular mechanisms in neuronal exocytosis have identified several proteins that participate in synaptic-vesicle exocytosis. By localizing these proteins with immunohistochemical methods, information about the capacity for synaptic exocytosis should be obtained. Here, antibodies directed against some of the exocytosis-related proteins were used to investigate whether they are present in nerve fibers within the dentinal tubules in rat molars. Antibodies against synaptosome-associated protein of 25 kDa, Rab 3, synaptotagmin and synapsin all produced a punctuate staining pattern, suggesting that the proteins are accumulated in bouton-like elements. The results demonstrate that a set of exocytosis-related proteins is accumulated in the dentinal tubules, most probably within the intradentinal nerves. This finding is consistent with the hypothesis that intradentinal nerves can mediate efferent signals.
Collapse
Affiliation(s)
- T Norlin
- Department of Basic Oral Sciences, Karolinska Institutet, Stockholm, Sweden.
| | | | | |
Collapse
|
19
|
Henery RJ, Robinson J, Bennett MR. Methods for grouping shapes of synaptic currents recorded from sets of synapses. J Neurosci Methods 1998; 86:79-90. [PMID: 9894788 DOI: 10.1016/s0165-0270(98)00148-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Synaptic currents due to transmitter release at sets of synapses, such as those formed by a single nerve terminal on adjacent smooth muscle cells or a nerve terminal on a dendrite, possess different amplitudes and time courses, that is different shapes. It is possible that different shape groupings exist that may be each associated with a particular synapse in the set recorded from. Two methods, involving the distance between two synaptic currents, namely multidimensional scaling and hierarchical clustering, were used to suggest possible groupings. A test of differences between a pair of synaptic currents was developed by comparing the distances from pairs of synaptic currents with the distances from pairs of failures from the same experiment. This allowed observation of significance levels between and within the suggested groups. These methods were applied to loose-patch recordings of excitatory junctional currents (EJCs) in mouse vas deferens made with extracellular electrodes, some of which were visualised using DiOC2(5) staining to identify varicosities. Groups of EJC shapes could be distinguished supporting a hypothesis of several categories of shapes. However, each method showed that the number of shape-groupings was much larger than the number of visualised varicosities. Possible reasons for this discrepancy are analysed, including a model in which different shape groupings can be generated by a single synaptic site.
Collapse
Affiliation(s)
- R J Henery
- The Department of Physiology, The Institute for Biomedical Research, The University of Sydney, NSW, Australia
| | | | | |
Collapse
|
20
|
Abstract
The autonomic neuromuscular junction at a varicosity in the vas deferens is defined by the localization of the vesicle-associated protein syntaxin in high concentrations in the axolemma and a high density of P2x1 receptors in a cluster beneath the varicosity. Calcium fluxes have been observed in all individual varicosities of a nerve terminal on the arrival of an impulse even though recordings made from these varicosities of the electrical signs of transmission with loose-patch electrodes over the varicosities show that they have very different probabilities for the secretion of a quantum. The fact that some varicosities seldom release a quantum on the arrival of an impulse is supported by the observation that antibodies against the N-terminus of synaptotagmin, which uniquely label the inside of synaptic vesicles when they undergo exocytosis, fail to do so in some varicosities during nerve stimulation whereas they do in others. It is suggested that the probability for secretion from a varicosity depends on the number of secretosomes that the varicosity possesses, where a secretosome is a complex of syntaxin, synaptotagmin, an N-type calcium channel, and a synaptic vesicle.
Collapse
Affiliation(s)
- M R Bennett
- Department of Physiology, Institute for Biomedical Research, University of Sydney, NSW, Australia.
| | | | | |
Collapse
|
21
|
Smith PG, Marzban F. Parasympathetic varicosity proliferation and synaptogenesis in rat eyelid smooth muscle after sympathectomy. Brain Res 1998; 786:171-80. [PMID: 9555000 DOI: 10.1016/s0006-8993(97)01439-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Parasympathetic innervation to eyelid smooth muscle inhibits sympathetic neurotransmission pre-junctionally without appreciable direct post-junctional effects. However, 5 weeks after sympathectomy, parasympathetic stimulation elicits substantial cholinergically mediated contractions. This study examined ultrastructural changes accompanying the conversion to parasympathetic excitation. In intact muscles, 64+/-9 nerve varicosities were encountered per 104 micron2. Most were close to muscle cells and not fully enclosed by supporting cells. Axo-axonal synapses were observed occasionally. Two days following sympathectomy, varicosity numbers were reduced by 97% and, relative to controls, remaining varicosities were farther from muscle cells and more frequently fully enclosed by supporting cells, but contained greater numbers of small spherical and large dense vesicles. By 6 weeks post-sympathectomy, numbers of varicosities per unit muscle volume increased to 14% of controls. These varicosities differed from those at 2 days in being closer to smooth muscle cells, less frequently enclosed, and having fewer small vesicles. These findings indicate that intact eyelid smooth muscle varicosities are predominantly sympathetic, but a small number of parasympathetic varicosities are present, some of which may form pre-junctional synapses with sympathetic nerves. Between 2 days and 6 weeks post-sympathectomy, varicosities increased in number and established appositions with smooth muscle cells. This suggests that parasympathetic nerves are capable of re-innervating an atypical smooth muscle target after sympathectomy, and that parasympathetic synaptogenesis is likely to contribute to conversion from pre-junctional inhibition to post-junctional excitation after sympathectomy.
Collapse
Affiliation(s)
- P G Smith
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160-7401, USA.
| | | |
Collapse
|
22
|
SANDOW SHAUNL, WHITEHOUSE DREW, HILL CARYLE. Specialised sympathetic neuroeffector associations in rat iris arterioles. J Anat 1998; 192 ( Pt 1):45-57. [PMID: 9568560 PMCID: PMC1467738 DOI: 10.1046/j.1469-7580.1998.19210045.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Vascular sympathetic neuroeffector associations have been examined in rat iris arterioles using serial section electron microscopy and reconstruction techniques. Examination of random sections showed that, of all profiles of varicosities (199) seen to lie closer than 4 microns to vascular smooth muscle cells, only a small proportion (29/199) were found in close association with vascular smooth muscle cells, where adjacent membranes were separated by less than 100 nm. However, serial section examination, from intervaricose region to intervaricose region, of 79 varicosities similarly observed lying within 4 microns of vascular smooth muscle cells showed that 54 formed close associations with vascular smooth muscle cells. In serial sections, all these varicosities were also closely associated with melanocytes and of the 25 remaining varicosities, 22 formed close associations with melanocytes alone, whilst 3 did not come into close association with any effector cell. The increased observation of close associations with vascular smooth muscle cells in serial sections, compared with random sections, is consistent with the demonstration that the area of contact only occupies, on average, a small percentage (5%) of the total surface area of the varicosity as seen in the 3-dimensional reconstructions. In both random and serial sections, close associations were observed between varicosities and vascular smooth muscle cells or melanocytes irrespective of whether fibres were present singly or in small nerve bundles. Three-dimensional reconstruction of associations of varicosities and vascular smooth muscle cells demonstrated several common features, such as accumulations of synaptic vesicles and loss of Schwann cell covering at the region of membrane facing the effector cell. The similarity in the appearance of the neuroeffector association seen in this study and those described in previous studies provides evidence for the existence of a common sympathetic neuroeffector association, irrespective of the receptor subtype involved in neurotransmission.
Collapse
Affiliation(s)
- SHAUN L.
SANDOW
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Australian National University Supercomputer Facility, Australian National University, A.C.T., Australia +61 2 6249 2687; e-mail:
- Correspondence to Dr Shaun Sandow, Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra, A.C.T., 0200 Australia. Tel: +61 2 6249 4782
| | - DREW WHITEHOUSE
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Australian National University Supercomputer Facility, Australian National University, A.C.T., Australia +61 2 6249 2687; e-mail:
| | - CARYL E.
HILL
- Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Australian National University Supercomputer Facility, Australian National University, A.C.T., Australia +61 2 6249 2687; e-mail:
| |
Collapse
|
23
|
Bennett MR. Neuromuscular transmission at an active zone: the secretosome hypothesis. JOURNAL OF NEUROCYTOLOGY 1996; 25:869-91. [PMID: 9023731 DOI: 10.1007/bf02284848] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- M R Bennett
- Department of Physiology, University of Sydney, NSW, Australia
| |
Collapse
|