Intermediolateral Column Research Articles

Hypothalamus-sympathetic-liver axis mediates the early phase of stress-induced hyperglycemia in the male mice

Rapid glucose supply is crucial for animal survival during stress response. How the timescale of stress-induced glucose release precisely controlled by hypothalamic corticotropin-releasing hormone (CRH) neurons remains unclear. Here, we show that stress-induced hyperglycemia can be divided into at least two stages in male mice: the first fast stage is mediated by hypothalamus (paraventricular to ventromedial hypothalamus)-sympathetic (raphe pallidus nucleus to intermediolateral nucleus)-liver (HSL) axis activity; the second delayed stage is mediated by adrenal activity. Blocking the activity of HSL axis impairs predatory evoked flight responses, indicating that the HSL pathway activity is necessary for stress coping. We further reveal the intracellular signal cascade for CRH signal in the hypothalamus, which is mediated by GABAA receptor β3 subunit phosphorylation at S408/409, results in prevention of GABAA receptor membrane recruitment. Thus, we uncovered the precise timescale of glucose supply during stress which is mediated by adrenal independent HSL and adrenal dependent pathway respectively.

The parasympathetic and sensory innervation of the proximal and distal colon in male mice.

The distributions of extrinsic neurons innervating the colon show differences in experimental animals from humans, including the vagal and spinal parasympathetic innervation to the distal colon. The neuroanatomical tracing to the mouse proximal colon has not been studied in details. This study aimed to trace the locations of extrinsic neurons projecting to the mouse proximal colon compared to the distal colon using dual retrograde tracing. The parasympathetic and sensory neurons projecting to colon were assessed using Cholera Toxin subunit B conjugated to Alexa-Fluor 488 or 555 injected in the proximal and distal colon of the same mice. Retrograde tracing from the proximal and distal colon labeled neurons in the dorsal motor nucleus of the vagus (DMV) and the nodose ganglia, while the tracing from the distal colon did not label the parasympathetic neurons in the lumbosacral spinal cord at L6-S1. Neurons in the pelvic ganglia which were cholinergic projected to the distal colon. There were more neurons in the DMV and nodose ganglia projecting to the proximal than distal colon. The right nodose ganglion had a higher number of neurons than the left ganglion innervating the proximal colon. In the dorsal root ganglia (DRG), the highest number of neurons traced from the distal colon were at L6, and those from the proximal colon at T12. DRG neurons projected closely to the cholinergic neurons in the intermediolateral column of L6 spinal cord. Small percentages of neurons with dual projections to both the proximal and distal colon existed in the DMV, nodose ganglia and DRG. We also observed long projecting neurons traced from the caudal distal colon to the transverse and proximal colon, some of which were calbindin immunoreactive, while there were no retrogradely labeled neurons traced from the proximal to distal colon. These data demonstrated that the vagal motor and motor and sensory neurons innervate both the proximal and distal colon in mice, and the autonomic neurons in the intermediate zone of the lumbosacral spinal cord do not project directly to the mouse colon, which differs from that in humans.

Neuregulin4-ErbB4 signalling pathway is driven by electroacupuncture stimulation to remodel brown adipose tissue innervation.

To show that electroacupuncture stimulation (ES) remodels sympathetic innervation in brown adipose tissue (BAT) via the bone morphogenic protein 8B (BMP8B)-neuregulin 4 (NRG4)-ErbB4 axis, with somatotopic dependence. We established a high-fat diet (HFD) model with C57BL/6J mice to measure the thermogenesis and metabolism of BAT. In addition, the sympathetic nerve activity (SNA) was measured with the electrophysiological technique, and the immunostaining of c-Fos was used to detect the central nervous system sources of sympathetic outflows. Finally, the key role of the BMP8B-NRG4-ErbB4 axis was verified by peripheral specific antagonism of ErbB4. ES at the forelimb and abdomen regions significantly up-regulate SNA, whereas ES at the hindlimb region has a limited regulatory effect on SNA but still partially restores HFD-induced BAT dysfunction. Mechanistically, ES at the forelimb and abdomen regions driving catecholaminergic signals in brown adipocytes depends on neural activities projected from the ventromedial nucleus of the hypothalamus (VMH) to the spinal cord intermediolateral column (IML). Notably, the peripheral suppression of ErbB4 in BAT inhibits the thermogenesis and metabolic function of BAT, as well as significantly hindering the SNA activation and metabolic benefits induced by ES. These results suggest that ES appears to be an effective approach for remodeling sympathetic innervation in BAT, which is closely related to neuronal activity in the VMH and the NRG4-ErbB4 signaling pathway.

Topography of the GLP-1/GLP-1 receptor system in the spinal cord of male mice

Glucagon-like peptide-1 receptor (GLP-1R) agonists are now commonly used to treat type 2 diabetes and obesity. GLP-1R signaling in the spinal cord has been suggested to account for the mild tachycardia caused by GLP-1R agonists, and may also be involved in the therapeutic effects of these drugs. However, the neuroanatomy of the GLP-1/GLP-1R system in the spinal cord is still poorly understood. Here we applied in situ hybridization and immunohistochemistry to characterize this system, and its relation to cholinergic neurons. GLP-1R transcript and protein were expressed in neuronal cell bodies across the gray matter, in matching distribution patterns. GLP-1R-immunolabeling was also robust in dendrites and axons, especially in laminae II–III in the dorsal horn. Cerebrospinal fluid-contacting neurons expressed GLP-1R protein at exceedingly high levels. Only small subpopulations of cholinergic neurons expressed GLP-1R, including a subset of sympathetic preganglionic neurons at the rostral tip of the intermediolateral nucleus. GLP-1 axons innervated all regions where GLP-1R neurons were distributed, except laminae II–III. Scattered preproglucagon (Gcg) mRNA-expressing neurons were identified in the cervical and lumbar enlargements. The results will facilitate further studies on how GLP-1 regulates the sympathetic system and other autonomic and somatic functions via the spinal cord.

Developmental Anatomy of Gray Matter of Spinal Cord in Animals with Special Reference to Prenatal Goat: A Review

Spinal cord is the major nerve tract of vertebrates, extending from the brain through the vertebral canal. Primordium, the neural tube was initially with thick lateral walls having three layers: inner germinal/ependymal layer, middle mantle layer forming the gray matter and outer marginal layer forming white matter. It presented a diamond-shaped lumen with a sulcus limitans, alar, basal, roof and floor plates and limiting membranes. Gray matter of the cord occupies the central region of spinal cord and in amniotes has in cross section, the well-known ‘H’ or butterfly-like shape. The white matter forms a thick peripheral zone of the cord and is divided by the gray columns into dorsal, lateral and ventral funiculi. There are three coumns for the gray matter, viz. the dorsal, ventral and lateral horns, with ventral ones being wider at the enlargements of the cord. Lateral horn appears only at thoracic, anterior lumbar and middle sacral levels. The layers of gray matter were laminae I to X. Lamina I or marginal zone capped the dorsal horn. Lamina II represented substantia gelatinosa and covered the dorsal horn, beneath marginal zone. Lamina III was an area with loosely arranged larger cells, entering the substantia gelatinosa. Lamina IV was a poorly defined cell column with nucleus proprius. Lamina V was a broad zone extending across the cervix of the dorsal horn; had spinal reticular nucleus and reticular processes. The region showed small to medium-sized cells which were most numerous in the zone between the ventral part of the dorsal horn and the lateral funiculus of white matter. Lamina VI was broad with unclear boundaries, related medially to central canal. It had compact medial and less compact lateral zones. Lamina VII shows the intermediate gray matter, with intermediolateral and intermediomedial nuclei, cervical nucleus of Stilling and Clark’s column. Lamina VIII had cells of small and medium size and was not sharply distinguished from lamina VII. Lamina IX had alpha and gamma type of neurons, which were larger at enlargements. Ventral horn had lateral and medial nuclear groups of multipolar neurons. Medial nuclear groups were seen in all regions and lateral groups only at enlargements. Medial nuclear group had dorsomedial and ventromedial nuclei; whereas the smaller lateral nuclear group had dorsolateral and ventrolateral nuclei. In addition, the enlargements also had central and retrodorsolateral nuclei. Lamina X was seen around the central canal. Laminae varied in cell size and thickness between regions of the cord. Development of laminae and nuclei of spinal gray in fetuses corresponded to the progressive growth of muscles and skeleton. All the ten laminae were together present in the spinal gray matter by the end of gestation.

Electroacupuncture reduced airway inflammation by activating somatosensory-sympathetic pathways in allergic asthmatic rats.

Electroacupuncture (EA) treatment is efficacious in patients with respiratory disorders, although the mechanisms of its action in lung-function protection are poorly understood. This study aimed to explore the neuroanatomical mechanisms of EA stimulation at the BL13 acupoint (Feishu, EA-BL13) improvement in asthma. Allergic asthma was induced by intranasal 2.0% ovalbumin (OVA) instillation combined with intraperitoneal injection of the 10.0% OVA. The levels of interleukin (IL)-4 and IL-5 were detected by enzyme-linked immunosorbent assay. Hematoxylin and eosin and periodic acid-schiff stain were used to evaluate inflammatory cell infiltration and mucus secretion. Cellular oncogene fos induction in neurons after EA stimulation was detected by immunofluorescent staining. The mRNA expression levels of adrenergic receptors were quantified with real-time polymerase chain reaction. EA improved airway inflammation and mucus secretion mainly by activating somatosensory-sympathetic pathways (P<0.001). Briefly, the intermediolateral (IML) nuclei of the spinal cord received signals from somatic EA stimulation and then delivered the information via the sympathetic trunk to the lung. Excited sympathetic nerve endings in lung tissue released large amounts of catecholamines that specifically activated the β2 adrenergic receptor (β2AR) on T cells (P<0.01) and further decreased the levels of IL-4 and IL-5 (P<0.001) through the cyclic adenosine monophosphate/protein kinase A signaling pathway. This study provided a new explanation and clinical basis for the use of EA-BL13 as a treatment for allergic asthma in both the attack and remission stages and other respiratory disorders related to airway inflammation.

Nerve transfer for restoration of lower motor neuron-lesioned bladder, urethral and anal sphincter function. Part 4: Effectiveness of the motor reinnervation.

In pilot work, we showed that somatic nerve transfers can restore motor function in long-term decentralized dogs. We continue to explore the effectiveness of motor reinnervation in 30 female dogs. After anesthesia, 12 underwent bilateral transection of coccygeal and sacral (S) spinal roots, dorsal roots of lumbar (L)7, and hypogastric nerves. Twelve months postdecentralization, eight underwent transfer of obturator nerve branches to pelvic nerve vesical branches, and sciatic nerve branches to pudendal nerves, followed by 10 mo recovery (ObNT-ScNT Reinn). The remaining four were euthanized 18 mo postdecentralization (Decentralized). Results were compared with 18 Controls. Squat-and-void postures were tracked during awake cystometry. None showed squat-and-void postures during the decentralization phase. Seven of eight ObNT-ScNT Reinn began showing such postures by 6 mo postreinnervation; one showed a return of defecation postures. Retrograde dyes were injected into the bladder and urethra 3 wk before euthanasia, at which point, roots and transferred nerves were electrically stimulated to evaluate motor function. Upon L2-L6 root stimulation, five of eight ObNT-ScNT Reinn showed elevated detrusor pressure and four showed elevated urethral pressure, compared with L7-S3 root stimulation. After stimulation of sciatic-to-pudendal transferred nerves, three of eight ObNT-ScNT Reinn showed elevated urethral pressure; all showed elevated anal sphincter pressure. Retrogradely labeled neurons were observed in L2-L6 ventral horns (in laminae VI, VIII, and IX) of ObNT-ScNT Reinn versus Controls in which labeled neurons were observed in L7-S3 ventral horns (in lamina VII). This data supports the use of nerve transfer techniques for the restoration of bladder function.NEW & NOTEWORTHY This data supports the use of nerve transfer techniques for the restoration of bladder function.

Terminal organization of the corticospinal projection from the arm/hand region of the rostral primary motor cortex (M1r or old M1) to the cervical enlargement (C5-T1) in rhesus monkey.

High-resolution anterograde tracers and stereology were used to study the terminal organization of the corticospinal projection (CSP) from the rostral portion of the primary motor cortex (M1r) to spinal levels C5-T1. Most of this projection (90%) terminated contralaterally within laminae V-IX, with the densest distribution in lamina VII. Moderate bouton numbers occurred in laminae VI, VIII, and IX with few in lamina V. Within lamina VII, labeling occurred over the distal-related dorsolateral subsectors and proximal-related ventromedial subsectors. Within motoneuron lamina IX, most terminations occurred in the proximal-related dorsomedial quadrant, followed by the distal-related dorsolateral quadrant. Segmentally, the contralateral lamina VII CSP gradually declined from C5-T1 but was consistently distributed at C5-C7 in lamina IX. The ipsilateral CSP ended in axial-related lamina VIII and adjacent ventromedial region of lamina VII. These findings demonstrate the M1r CSP influences distal and proximal/axial-related spinal targets. Thus, the M1r CSP represents a transitional CSP, positioned between the caudal M1 (M1c) CSP, which is 98% contralateral and optimally organized to mediate distal upper extremity movements (Morecraft etal., 2013), and dorsolateral premotor (LPMCd) CSP being 79% contralateral and optimally organized to mediate proximal/axial movements (Morecraft etal., 2019). This distal to proximal CSP gradient corresponds to the clinical deficits accompanying caudal to rostral motor cortex injury. The lamina IX CSP is considered in the light of anatomical and neurophysiological evidence which suggests M1c gives rise to the major proportion of the cortico-motoneuronal (CM) projection, while there is a limited M1r CM projection.

Abstract 17051: Oxytocin Receptor in the Spinal Neuraxial Modulation of Ventricular Excitability

Introduction: Cardiac sympathoexcitation is a major contributor to the pathogenesis of ventricular tachyarrhymias (VTs) during ischemia reperfusion (I/R) and chronic myocardial infarction (MI). Afferent network connections in the intermediolateral cell column (IML) and dorsal horn (DH) control sympathetic output to the heart. Our team reported spinal cord stimulation (SCS), decreased cardiac sympathoexcitation and reduced VTs during ischemia. Oxytocin (OXT) is a known neuromodulator; however, whether OXT signaling can modulate the cardiospinal neural network is unknown. Hypothesis: SCS neuromodulation is reducing sympathoexcitation and VTs through OXT signaling pathways. Methods: Two models of cardiac ischemia were used in Yorkshire domestic swine. In acute I/R, a suture was placed around the left anterior descending (LAD) coronary artery, after sternotomy. Chronic infarction (MI) was created by accessing the femoral with fluoroscopy guidance. Polystyrene microspheres (1ml) were injected via a 3mm angioplasty balloon catheter to the LAD. Animals then recovered post-MI for 6-8wk. SCS treatment was delivered through a four-pole lead which was inserted in the epidural space (T1-T4)(50Hz, 0.4ms pulse duration). T2-T4 spinal cord was collected postmortem for molecular analysis. Fluorescence in situ hybridization (FISH) protocol for RNAscope Fluorescent v2 Assay (ACD) was followed. Cell counts represented as 3 puncta or more centered around DAPI. Results: We report that OXT receptor positive cells significantly decreased as a result of I/R and MI (p&lt;0.001, two-way ANOVA n=4-5 animals, average of 2-3 slices per animal). Within the DH the majority of OXT positive cells were inhibitory GABAergic neurons. Within the IML, a majority of the cells regulated by I/R and MI were microglia, and both an inhibitory and excitatory population contributed to the onset of ischemia. SCS treatment after I/R and MI resulted in the recovery of this OXT receptor cell population. Conclusions: By evaluating the role of OXT in reducing cardiac sympathoexcitation at the level of the spinal cord, we provide new insights into optimizing current neuromodulation approaches and developing new pharmacologic therapies.

The Essential Interconnection of the Reticular Formation, Intermediolateral Nucleus, and Hypothalamus-Pituitary-Adrenal Axis: A Comprehensive View on Cellular Homeostasis

This paper explores the hypothesis that the Intermediolateral Nucleus, by possessing a direct and unique connection with the adrenal medulla, stands in contrast to the two-neuron pathway typical of the Sympathetic Nervous System. This distinctive characteristic of the Intermediolateral Nucleus may play a crucial role in counter-entropic and cellular energy regulation. The Reticular Formation, extending from the brainstem to the start of the cervical spinal cord, is vital for the regulation of heart rate, breathing, and cognitive functions, facilitating continuous chemical interaction throughout the body and being pivotal for energy regulation. The Hypothalamic-Pituitary-Adrenal Axis, as the primary response mechanism to cellular challenges, holds a central role in energy regulation, countering entropic processes, and supporting vital bioenergetic complexities for survival. The intimate collaboration between the Reticular Formation, the Intermediolateral Nucleus, and the Hypothalamic-PituitaryAdrenal Axis is essential for the continuous process of adjustments and readaptations, enabling the organism to respond and adapt to constant changes in both internal and external environments. This study deepens our understanding of homeostasis and the synergistic interaction between these structures in the vital process of maintaining homeostasis and energy regulation.

Thoracic Dorsal Root Ganglion Application of Resiniferatoxin Reduces Myocardial Ischemia-Induced Ventricular Arrhythmias.

A myocardial ischemia/reperfusion (IR) injury activates the transient receptor potential vanilloid 1 (TRPV1) dorsal root ganglion (DRG) neurons. The activation of TRPV1 DRG neurons triggers the spinal dorsal horn and the sympathetic preganglionic neurons in the spinal intermediolateral column, which results in sympathoexcitation. In this study, we hypothesize that the selective epidural administration of resiniferatoxin (RTX) to DRGs may provide cardioprotection against ventricular arrhythmias by inhibiting afferent neurotransmission during IR injury. Yorkshire pigs (n = 21) were assigned to either the sham, IR, or IR + RTX group. A laminectomy and sternotomy were performed on the anesthetized animals to expose the left T2-T4 spinal dorsal root and the heart for IR intervention, respectively. RTX (50 μg) was administered to the DRGs in the IR + RTX group. The activation recovery interval (ARI) was measured as a surrogate for the action potential duration (APD). Arrhythmia risk was investigated by assessing the dispersion of repolarization (DOR), a marker of arrhythmogenicity, and measuring the arrhythmia score and the number of non-sustained ventricular tachycardias (VTs). TRPV1 and calcitonin gene-related peptide (CGRP) expressions in DRGs and CGRP expression in the spinal cord were assessed using immunohistochemistry. The RTX mitigated IR-induced ARI shortening (-105 ms ± 13 ms in IR vs. -65 ms ± 11 ms in IR + RTX, p = 0.028) and DOR augmentation (7093 ms2 ± 701 ms2 in IR vs. 3788 ms2 ± 1161 ms2 in IR + RTX, p = 0.020). The arrhythmia score and VT episodes during an IR were decreased by RTX (arrhythmia score: 8.01 ± 1.44 in IR vs. 3.70 ± 0.81 in IR + RTX, p = 0.037. number of VT episodes: 12.00 ± 3.29 in IR vs. 0.57 ± 0.3 in IR + RTX, p = 0.002). The CGRP expression in the DRGs and spinal cord was decreased by RTX (DRGs: 6.8% ± 1.3% in IR vs. 0.6% ± 0.2% in IR + RTX, p < 0.001. Spinal cord: 12.0% ± 2.6% in IR vs. 4.5% ± 0.8% in IR + RTX, p = 0.047). The administration of RTX locally to thoracic DRGs reduces ventricular arrhythmia in a porcine model of IR, likely by inhibiting spinal afferent hyperactivity in the cardio-spinal sympathetic pathways.

Reorganization of corticospinal projections after prominent recovery of finger dexterity from partial spinal cord injury in macaque monkeys.

We investigated morphological changes in the corticospinal tract (CST) to understand the mechanism underlying recovery of hand function after lesion of the CST at the C4/C5 border in 7 macaque monkeys. All monkeys exhibited prominent recovery of precision grip success ratio within a few months. The trajectories and terminals of CST from the contralesional (n = 4) and ipsilesional (n = 3) hand area of primary motor cortex (M1) were investigated at 5-29 months after the injury using an anterograde neural tracer, biotinylated dextran amine (BDA). Reorganization of the CST was assessed by counting the number of BDA-labeled axons and bouton-like swellings in the gray and white matters. Rostral to the lesion (at C3), the number of axon collaterals of the descending axons from both contralesional and ipsilesional M1 entering the ipsilesional and contralesional gray matter, respectively, were increased. Caudal to the lesion (at C8), axons originating from the contralesional M1, descending in the preserved gray matter around the lesion, and terminating in ipsilesional laminae VI/VII and IX were observed. In addition, axons and terminals from the ipsilesional M1 increased in the ipsilesional laminae IX after recrossing the midline, which were not observed in intact monkeys. Conversely, axons originating from the ipsilesional M1 and directed toward the contralesional laminae VII decreased. These results suggest that multiple reorganizations of the corticospinal projections to spinal segments both rostral and caudal to the lesion originating from bilateral M1 underlie a prominent recovery in long-term after spinal cord injury.SIGNIFICANCE STATEMENTPrevious studies have shown that dexterous finger movements recover prominently after lesion of the corticospinal tract (CST) at the mid-cervical segments through rehabilitative training in macaque monkeys. Here, we show reorganization of the CST including sprouting of axons originating from the contralesional and ipsilesional motor cortex in the gray matter both caudal and rostral to the lesion, including a re-direction of the CST to hand motoneurons in the monkeys 5-29 months after the lesion. Thus, multiple mechanisms of reorganization of CST axons underlie the recovery of impaired cortico-motoneuronal pathways for the long-term recovery of finger dexterity.

DISTRIBUTION OF PARVALBUMIN-EXPRESSING NEURONAL POPULATIONS IN THE CAT CERVICAL AND LUMBAR SPINAL CORD GRAY MATTER

Parvalbumin is a classical marker of interneuronal populations in the central nervous system. Analyzing the cervical and lumbar spinal cord segments of cats (Felis catus), both individual cells and entire populations of neurons expressing parvalbumin were identified in most of the gray matter laminae. These populations have strict laminar and nuclear localization. Numerous neuronal clusters are located in the medial part of lamina V–VI and in laminae VII of cervical and lumbar enlargements. We believe that the first one located in segments C4–C8 and L4–L7 may participate in the modulatory mechanisms of locomotor activity via the convergence of cutaneous and proprioceptive afferentation from the limbs. Neuronal populations in lamina VII consist of Ia interneurons and Renshaw interneurons that participate in the motoneuron inhibition. Less numerous populations of parvalbumin-immunopositive cells found in laminae III possibly participated in the regulation of cutaneous sensitivity. Another population located in lamina VIII possibly forms commissural and propriospinal connections and participates in modulating the activity of motoneurons. Immunopositive interneurons also revealed in the precerebellar nuclei: central cervical nucleus and Clarke’s nucleus; unlike the general population of these nuclei, neurons revealed are interneurons. Scarce immunopositive cells are found in lamina I of L6–L7 segments, as well as in laminae II, IV, and X of all segments investigated.

Spinal neuromodulation mitigates myocardial ischemia-induced sympathoexcitation by suppressing the intermediolateral nucleus hyperactivity and spinal neural synchrony.

Myocardial ischemia disrupts the cardio-spinal neural network that controls the cardiac sympathetic preganglionic neurons, leading to sympathoexcitation and ventricular tachyarrhythmias (VTs). Spinal cord stimulation (SCS) is capable of suppressing the sympathoexcitation caused by myocardial ischemia. However, how SCS modulates the spinal neural network is not fully known. In this pre-clinical study, we investigated the impact of SCS on the spinal neural network in mitigating myocardial ischemia-induced sympathoexcitation and arrhythmogenicity. Ten Yorkshire pigs with left circumflex coronary artery (LCX) occlusion-induced chronic myocardial infarction (MI) were anesthetized and underwent laminectomy and a sternotomy at 4-5 weeks post-MI. The activation recovery interval (ARI) and dispersion of repolarization (DOR) were analyzed to evaluate the extent of sympathoexcitation and arrhythmogenicity during the left anterior descending coronary artery (LAD) ischemia. Extracellular in vivo and in situ spinal dorsal horn (DH) and intermediolateral column (IML) neural recordings were performed using a multichannel microelectrode array inserted at the T2-T3 segment of the spinal cord. SCS was performed for 30 min at 1 kHz, 0.03 ms, 90% motor threshold. LAD ischemia was induced pre- and 1 min post-SCS to investigate how SCS modulates spinal neural network processing of myocardial ischemia. DH and IML neural interactions, including neuronal synchrony as well as cardiac sympathoexcitation and arrhythmogenicity markers were evaluated during myocardial ischemia pre- vs. post-SCS. ARI shortening in the ischemic region and global DOR augmentation due to LAD ischemia was mitigated by SCS. Neural firing response of ischemia-sensitive neurons during LAD ischemia and reperfusion was blunted by SCS. Further, SCS showed a similar effect in suppressing the firing response of IML and DH neurons during LAD ischemia. SCS exhibited a similar suppressive impact on the mechanical, nociceptive and multimodal ischemia sensitive neurons. The LAD ischemia and reperfusion-induced augmentation in neuronal synchrony between DH-DH and DH-IML pairs of neurons were mitigated by the SCS. These results suggest that SCS is decreasing the sympathoexcitation and arrhythmogenicity by suppressing the interactions between the spinal DH and IML neurons and activity of IML preganglionic sympathetic neurons.

Interrelationships Between Spinal Sympathetic Preganglionic Neurons, Autonomic Systems and Electrical Synapses Formed by Connexin36-containing Gap Junctions

Spinal sympathetic preganglionic neurons (SPNs) are among the many neuronal populations in the mammalian central nervous system (CNS) where there is evidence for electrical coupling between cell pairs linked by gap junctions composed of connexin36 (Cx36). Understanding the organization of this coupling in relation to autonomic functions of spinal sympathetic systems requires knowledge of how these junctions are deployed among SPNs. Here, we document the distribution of immunofluorescence detection of Cx36 among SPNs identified by immunolabelling of their various markers, including choline acetyltransferase, nitric oxide and peripherin in adult and developing mouse and rat. In adult animals, labelling of Cx36 was exclusively punctate and dense concentrations of Cx36-puncta were distributed along the entire length of the spinal thoracic intermediolateral cell column (IML). These puncta were also seen in association with SPN dendritic processes in the lateral funiculus, the intercalated and central autonomic areas and those within and extending medially from the IML. All labelling for Cx36 was absent in spinal cords of Cx36 knockout mice. High densities of Cx36-puncta were already evident among clusters of SPNs in the IML of mouse and rat at postnatal days 10–12. In Cx36BAC::eGFP mice, eGFP reporter was absent in SPNs, thus representing false negative detection, but was localized to some glutamatergic and GABAergic synaptic terminals. Some eGFP+ terminals were found contacting SPN dendrites. These results indicate widespread Cx36 expression in SPNs, further supporting evidence of electrical coupling between these cells, and suggest that SPNs are innervated by neurons that themselves may be electrically coupled.

Spinal neuromodulation by intrathecal oxytocin administration mitigates the myocardial ischemia induced sympathoexcitation by suppressing the ischemia-related spinal neural hyperactivity

Background: Myocardial ischemia can lead to fatal ventricular arrhythmias by disrupting the cardiospinal neural network which controls the sympathoexcitation. Spinal neuromodulation techniques could decrease myocardial ischemia-induced sympathoexcitation by modulating the spinal neural network. Hypothesis: We hypothesize that spinal oxytocin (OXT) administration decreases myocardial ischemia-induced sympathoexcitation by suppressing spinal neural hyperactivity in the dorsal horn (DH) and intermediolateral nucleus regions (IML). Materials and Methods: Anesthetized pigs underwent laminectomy to expose the spinal T2 section and a sternotomy to expose the heart for performing left anterior descending coronary artery ischemia (LAD) with and without intrathecal oxytocin (90ug) treatment. Electrocardiograms were recorded using a 56-channel mesh electrode to evaluate the activation recovery interval (ARI) and dispersion of repolarization (DOR) which are the markers for sympathoexcitation and arrhythmogenecity. Extracellular in-vivo spinal neural recordings were done by using a 64-channel microelectrode array inserted at the T2 segment of the spinal cord to record the activity of DH and IML neurons. Oxytocin was administered intrathecally at T1-T3. Spinal neural activity, ARI, and DOR were evaluated during myocardial ischemia with vs. without intrathecal oxytocin administration. Results: Sixteen Yorkshire pigs entered into this study. In 13 animals (LAD:7, LAD+OXT:6) ARI and DOR were evaluated during long LAD ischemia (1hr). ARI shortening due to LAD was mitigated by OXT (LAD:-33 ± 4 ms; LAD+OXT: -15 ± 1 ms, P=0.001). OXT decreased the LAD-induced augmented DOR (LAD: 2194± 310 ms2; LAD+OXT: 1099± 305 ms2, P=0.029). We have further evaluated the effect of OXT on short LAD ischemia (5 mins) and the impact of intrathecal OXT agonist on the spinal cord neural processing of myocardial ischemia in 3 pigs. Out of 88 recorded neurons, LAD increased the firing rate of more neurons than the LAD+OXT (LAD: increased 52, decreased 12 neurons; LAD+OXT: increased 16, decreased 14 neurons, P=0.007). The LAD-induced spinal cord hyperactivity was mitigated after intrathecal OXT administration (LAD:1.57 ± 0.52 Hz to LAD+OXT: 0.02 ± 0.22 Hz, P=0.0001). OXT also mitigated the reperfusion-induced spinal neuronal hyperactivity (LAD:2.16 ± 0.59 Hz to LAD+OXT: -0.36 ± 0.28 Hz, P&lt;0.0001). OXT showed a similar effect in reducing the LAD-induced sympathoexcitation in these three animals (ARI shortening: LAD: -69 ± 14 ms; LAD+OXT: -38 ± 8 ms, P=0.035). Conclusion: Myocardial ischemia induces sympathoexcitation by increasing the spinal neural activity. OXT mitigates the adverse effect of myocardial ischemia by suppressing spinal neural hyperactivity. Funding: NIH (R01) HL136836 (Dr.Mahajan) and University of Pittsburgh Medical Center Competitive Medical Research Fund (Dr.Salavatian). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Emerging non-invasive therapeutic approaches targeting hypocholinergic neural systems in Parkinson's disease.

Emerging non-invasive therapeutic approaches targeting hypocholinergic neural systems in Parkinson's disease.

Distribution of Lewy-related pathology in the brain, spinal cord, and periphery: the population-based Vantaa 85 + study

Evolving evidence has supported the existence of two anatomically distinct Lewy-related pathology (LRP) types. Investigation of spinal cord and peripheral LRP can elucidate mechanisms of Lewy body disorders and origins of synuclein accumulation. Still, very few unselected studies have focused on LRP in these regions. Here we analysed LRP in spinal cord, dorsal root ganglion, and adrenal gland in the population-based Vantaa 85 + study, including every ≥ 85 years old citizen living in the city of Vantaa in 1991 (n = 601). Samples from spinal cord (C6-7, TH3-4, L3-4, S1-2) were available from 303, lumbar dorsal root ganglion from 219, and adrenal gland from 164 subjects. Semiquantitative scores of LRP were determined from immunohistochemically stained sections (anti-alpha-synuclein antibody 5G4). LRP in the ventral and dorsal horns of spinal cord, thoracic intermediolateral column, dorsal root ganglion and adrenal gland were compared with brain LRP, previously determined according to DLB Consortium criteria and by caudo-rostral versus amygdala-based LRP classification. Spinal LRP was found in 28% of the total population and in 61% of those who had LRP in the brain. Spinal cord LRP was found only in those subjects with LRP in the brain, and the quantity of spinal cord LRP was associated with the severity of brain LRP (p < 0.001). Unsupervised K-means analysis identified two cluster types of spinal and brain LRP corresponding to caudo-rostral and amygdala-based LRP types. The caudo-rostral LRP type exhibited more frequent and severe pathology in spinal cord, dorsal root ganglion and adrenal gland than the amygdala-based LRP type. Analysis of specific spinal cord regions showed that thoracic intermediolateral column and sacral dorsal horn were the most frequently affected regions in both LRP types. This population-based study on brain, spinal and peripheral LRP provides support to the concept of at least two distinct LRP types.

Study on the central neural pathway and the relationship between the heart and small intestine via a dual neural tracer.

Despite very different functions, studies increasingly report that there may be a potential central nervous anatomical connection between the heart and the small intestine. In this study, the central nervous anatomical relationship between the heart and small intestine was studied via a viral tracer. Pseudorabies virus (PRV) syngeneic strains with different fluorescent reporter genes (eGFP or mRFP) were microinjected into the heart walls and small intestinal walls of male C57BL/6J using glass microelectrode. The results showed that the co-labeled nuclei in the brain were lateral periaqueductal gray (LPAG) and ventrolateral periaqueductal gray (VLPAG) in the midbrain, mesencephalic trigeminal nucleus (Me5), and motor trigeminal nucleus anterior digastric Part (5Adi) in the pons. The co-labeled sites in the spinal cord were intermediolateral column (IML) in the second thoracic vertebra, IML and lamina 7 of the spinal gray (7SP) in the third thoracic vertebra, and IML in the fourth thoracic vertebra. Our data show that there is a neuroanatomical connection between the small intestine and the heart in the central nervous system (CNS). Neuroanatomical integration of the heart and small intestine may provide a basis for revealing the physiological and pathological interactions between the circulatory and digestive systems. The interactions may be mediated more effectively through sympathetic nerves.

The brain of the tree pangolin (Manis tricuspis). X. The spinal cord.

The spinal cord of the tree pangolin is known to be very short compared to the overall length of the body and tail. Here, we provide a description of the tree pangolin spinal cord to determine whether the short length contributes to specific structural, and potentially functional, differences. The short spinal cord of the adult tree pangolin, at around 13 cm, terminates at the midthoracic level. Within this shortened spinal cord, we could identify six regions, which from rostral to caudal include the prebrachial, brachial, interramal, crural, postcrural, and caudal regions, with both the brachial and crural regions showing distinct swellings. The chemoarchitecture of coronal sections through these regions confirmed regional assignation, being most readily delineated by the presence of cholinergic neurons forming the intermediolateral column in the interramal region and the sacral parasympathetic nucleus in the postcrural region. The 10 laminae of Rexed were observed throughout the spinal cord and presented with an anatomical organization similar to that observed in other mammals. Despite the shortened length of the tree pangolin spinal cord, the regional and laminar anatomical organization is very similar to that observed in other mammals. This indicates that the functional aspects of the short tree pangolin spinal cord can be inferred from what is known in other mammals.