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Stanchak KE, Miller KE, Shikiar D, Brunton BW, Perkel DJ. Mechanistic Hypotheses for Proprioceptive Sensing Within the Avian Lumbosacral Spinal Cord. Integr Comp Biol 2023; 63:474-483. [PMID: 37279454 DOI: 10.1093/icb/icad052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 05/14/2023] [Accepted: 05/24/2023] [Indexed: 06/08/2023] Open
Abstract
Animals need to accurately sense changes in their body position to perform complex movements. It is increasingly clear that the vertebrate central nervous system contains a variety of cells capable of detecting body motion, in addition to the comparatively well-understood mechanosensory cells of the vestibular system and the peripheral proprioceptors. One such intriguing system is the lower spinal cord and column in birds, also known as the avian lumbosacral organ (LSO), which is thought to act as a set of balance sensors that allow birds to detect body movements separately from head movements detected by the vestibular system. Here, we take what is known about proprioceptive, mechanosensory spinal neurons in other vertebrates to explore hypotheses for how the LSO might sense mechanical information related to movement. Although the LSO is found only in birds, recent immunohistochemical studies of the avian LSO have hinted at similarities between cells in the LSO and the known spinal proprioceptors in other vertebrates. In addition to describing possible connections between avian spinal anatomy and recent findings on spinal proprioception as well as sensory and sensorimotor spinal networks, we also present some new data that suggest a role for sensory afferent peptides in LSO function. Thus, this perspective articulates a set of testable ideas on mechanisms of LSO function grounded in the emerging spinal proprioception scientific literature.
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Affiliation(s)
| | - Kimberly E Miller
- Department of Biology, University of Washington, Seattle, WA 98195, USA
- Department of Psychology, University of Washington, Seattle WA 98195, USA
| | - Devany Shikiar
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - Bingni W Brunton
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - David J Perkel
- Department of Biology, University of Washington, Seattle, WA 98195, USA
- Department of Otolaryngology, University of Washington, Seattle, WA 98195, USA
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Kamska V, Daley M, Badri-Spröwitz A. 3D Anatomy of the Quail Lumbosacral Spinal Canal-Implications for Putative Mechanosensory Function. Integr Org Biol 2020; 2:obaa037. [PMID: 33791575 PMCID: PMC7810575 DOI: 10.1093/iob/obaa037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Birds are diverse and agile vertebrates capable of aerial, terrestrial, aquatic, and arboreal locomotion. Evidence suggests that birds possess a novel balance sensing organ in the lumbosacral spinal canal, a structure referred to as the "lumbosacral organ" (LSO), which may contribute to their locomotor agility and evolutionary success. The mechanosensing mechanism of this organ remains unclear. Here we quantify the 3D anatomy of the lumbosacral region of the common quail, focusing on establishing the geometric and biomechanical properties relevant to potential mechanosensing functions. We combine digital and classic dissection to create a 3D anatomical model of the quail LSO and estimate the capacity for displacement and deformation of the soft tissues. We observe a hammock-like network of denticulate ligaments supporting the lumbosacral spinal cord, with a close association between the accessory lobes and ligamentous intersections. The relatively dense glycogen body has the potential to apply loads sufficient to pre-stress denticulate ligaments, enabling external accelerations to excite tuned oscillations in the LSO soft tissue, leading to strain-based mechanosensing in the accessory lobe neurons. Considering these anatomical features together, the structure of the LSO is reminiscent of a mass-spring-based accelerometer.
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Affiliation(s)
- Viktoriia Kamska
- Dynamic Locomotion Group, Max Planck Institute for Intelligent Systems, 70569 Stuttgart, Germany
| | - Monica Daley
- Department of Ecology and Evolutionary Biology, University of California Irvine, Irvine, CA, USA
| | - Alexander Badri-Spröwitz
- Dynamic Locomotion Group, Max Planck Institute for Intelligent Systems, 70569 Stuttgart, Germany
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Stanchak KE, French C, Perkel DJ, Brunton BW. The Balance Hypothesis for the Avian Lumbosacral Organ and an Exploration of Its Morphological Variation. Integr Org Biol 2020; 2:obaa024. [PMID: 33791565 PMCID: PMC7751001 DOI: 10.1093/iob/obaa024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Birds (Aves) exhibit exceptional and diverse locomotor behaviors, including the exquisite ability to balance on two feet. How birds so precisely control their movements may be partly explained by a set of intriguing modifications in their lower spine. These modifications are collectively known as the lumbosacral organ (LSO) and are found in the fused lumbosacral vertebrae called the synsacrum. They include a set of transverse canal-like recesses in the synsacrum that align with lateral lobes of the spinal cord, as well as a dorsal groove in the spinal cord that houses an egg-shaped glycogen body. Based on compelling but primarily observational data, the most recent functional hypotheses for the LSO consider it to be a secondary balance organ, in which the transverse canals are analogous to the semicircular canals of the inner ear. If correct, this hypothesis would reshape our understanding of avian locomotion, yet the LSO has been largely overlooked in the recent literature. Here, we review the current evidence for this hypothesis and then explore a possible relationship between the LSO and balance-intensive locomotor ecologies. Our comparative morphological dataset consists of micro-computed tomography (μ-CT) scans of synsacra from ecologically diverse species. We find that birds that perch tend to have more prominent transverse canals, suggesting that the LSO is useful for balance-intensive behaviors. We then identify the crucial outstanding questions about LSO structure and function. The LSO may be a key innovation that allows independent but coordinated motion of the head and the body, and a full understanding of its function and evolution will require multiple interdisciplinary research efforts.
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Affiliation(s)
- K E Stanchak
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - C French
- Department of Biology, University of Washington, Seattle, WA 98195, USA
| | - D J Perkel
- Department of Biology, University of Washington, Seattle, WA 98195, USA
- Department of Otolaryngology, University of Washington, Seattle, WA 98195, USA
| | - B W Brunton
- Department of Biology, University of Washington, Seattle, WA 98195, USA
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Matsushita Y, Kitamura N, Higuchi M, Z Hosaka Y, Shibuya I. Neuron-like cells in the chick spinal accessory lobe express neuronal-type voltage-gated sodium channels. Biomed Res 2018; 39:189-196. [PMID: 30101839 DOI: 10.2220/biomedres.39.189] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Ten pairs of protrusions, called accessory lobes (ALs), exist at the lateral sides of the avian lumbosacral spinal cord. Histological evidence indicates that neuron-like cells gather in the ALs, and behavioral evidence suggests that the ALs act as a sensory organ of equilibrium during bipedal walking. Recently, using an electrophysiological method, we reported that cells showing Na+ currents and action potentials exist among cells that were dissociated from the ALs. However, it was unclear which isoforms of the voltage-gated sodium channel (VGSC) are expressed in the ALs and whether cells having neuronal morphology in the ALs express VGSCs. To elucidate these points, RT-PCR and immunohistochemical experiments were performed. In RT-PCR analysis, PCR products for Nav 1.1-1.7 were detected in the ALs. The signal intensities of the Nav 1.1 and 1.6 isoforms were stronger than those of the other isoforms. We confirmed that an antibody raised against an epitope peptide of the rat VGSC had cross-reactivity to chick tissues by Western blotting, and we performed immunofluorescence staining using the antibody. The AL contained cells having neuron-like morphology and VGSC-like immunoreactivity at their cytoplasm and/or cell membranes. Filament-like structures showing GFAP-like immunoreactivity infilled intercellular spaces. The VGSC- and GFAP-like immunoreactivities did not overlap. These results indicate that the neuronal isoforms of the VGSC are mainly expressed in the AL and that the neuron-like cells in the ALs express VGSCs. Our findings indicate that AL neurons generate action potentials and send sensory information to the motor systems on the contralateral side of the spinal segment.
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Affiliation(s)
- Yumi Matsushita
- Laboratory of Veterinary Physiology, Faculty of Agriculture, Tottori University
| | - Naoki Kitamura
- Laboratory of Veterinary Physiology, Faculty of Agriculture, Tottori University
| | - Masashi Higuchi
- Laboratory of Veterinary Biochemistry, Faculty of Agriculture, Tottori University
| | - Yoshinao Z Hosaka
- Laboratory of Veterinary Anatomy, Faculty of Agriculture, Tottori University
| | - Izumi Shibuya
- Laboratory of Veterinary Physiology, Faculty of Agriculture, Tottori University
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Takahashi K, Kitamura N, Suzuki Y, Yamanaka Y, Shinohara H, Shibuya I. Activation of muscarinic acetylcholine receptors elevates intracellular Ca(2+) concentrations in accessory lobe neurons of the chick. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2014; 201:385-94. [PMID: 25481714 DOI: 10.1007/s00359-014-0971-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 11/23/2014] [Accepted: 11/26/2014] [Indexed: 10/24/2022]
Abstract
Accessory lobes are protrusions located at the lateral sides of the spinal cord of chicks and it has been proposed that they play a role as a sensory organ for equilibrium during walking. We have reported that functional neurons exist in the accessory lobe. As there is histological evidence that synaptic terminals of cholinergic nerves exist near the somata of accessory lobe neurons, we examined the effects of acetylcholine on changes in intracellular Ca2+ concentrations ([Ca2+]i), as an index of cellular activities. Acetylcholine (0.1-100 µM) caused a transient rise in the [Ca2+]i. Acetylcholine-evoked [Ca2+]i rises were observed in the absence of extracellular Ca2+, and they were abolished in the presence of cyclopiazonic acid, an inhibitor of Ca2+-ATPase of intracellular Ca2+ stores or atropine, a muscarinic receptor antagonist. mRNAs coding M3 and M5 isoforms of the muscarinic receptors were detected in accessory lobes by the RT-PCR. These results indicate that chick accessory lobe neurons express functional muscarinic acetylcholine receptors, and that acetylcholine stimulates Ca2+ mobilization from intracellular Ca2+ stores, which elevates the [Ca2+]i in the somata of accessory lobe neurons, through activation of these receptors. Cholinergic synaptic transmission to the accessory lobe neurons may regulate some cellular functions through muscarinic receptors.
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Affiliation(s)
- Keita Takahashi
- Laboratory of Veterinary Physiology, Joint Department of Veterinary Medicine, Faculty of Agriculture, Tottori University, 4-101, Koyama-cho Minami, Tottori, 680-8553, Japan
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Voltage-gated Ca2+ channels in accessory lobe neurons of the chick. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2014; 200:739-48. [PMID: 24842482 DOI: 10.1007/s00359-014-0917-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 04/28/2014] [Accepted: 04/29/2014] [Indexed: 10/25/2022]
Abstract
Birds have ten pairs of protrusions, "accessory lobes", on the lateral sides of the lumbosacral spinal cord. It has been proposed that accessory lobes act as a sensory organ of equilibrium and neurons in accessory lobes transmit sensory information to the motor center. We have reported that cells in chick accessory lobes express functional voltage-gated Na(+) and K(+) channels and generate action potentials. In this study, we examined properties of voltage-gated Ca(2+) channels (VGCCs). The amplitude of voltage-gated Ca(2+) channel currents carried by Ca(2+) and Ba(2+) increased gradually during 10 min rather than showing the usual run-down. The current-voltage relationship of Ba(2+) currents was consistent with that of the high-voltage-activated Ca(2+) channel. The proportion of Ba(2+) currents inhibited by ω-conotoxin GVIA was larger than 80%, indicating that the major subtype is N type. Amplitudes of tail currents of Ca(2+) currents evoked by repetitive pulses at 50 Hz are stable for 1 s. If the major subtype of VGCCs at synaptic terminals is also N type, this property may contribute to the establishment of stable synaptic connections between accessory lobe neurons, which are reported to fire at frequencies higher than 15 Hz, and postsynaptic neurons in the spinal cord.
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Glutamate evokes firing through activation of kainate receptors in chick accessory lobe neurons. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2012; 199:35-43. [DOI: 10.1007/s00359-012-0766-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Revised: 09/26/2012] [Accepted: 09/30/2012] [Indexed: 10/27/2022]
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