Biology subjects

Dowaliby, L.

Publications and source records attributed to Dowaliby, L..

5 recordsLinked to original sources

bioRxiv2026

Aberrant Pain Phenotypes Emerge Following Prenatal Hypoxic-Ischemic Injury in a Rabbit Model of Cerebral Palsy

Cerebral Palsy (CP) is the most common motor disability in childhood, and the most frequent comorbidity is pain. Rabbit kits subjected to prenatal hypoxia-ischemia (HI) exhibit allodynia and an expansion of nociceptive afferents in the lumbar spinal cord at postnatal day (P5). In this study, we examined how HI alters the development of multiple sensory modalities and its effect on psychosocial measures and C-fiber distribution in the spinal cord. To do this, we performed an HI surgery to occlude blood flow to fetal New Zealand White rabbits for 40 minutes, or a sham surgery. We performed von Frey, Hargreaves, and a cold allodynia test at P1, P5, P11, and P18. Additionally, we performed open field, a two-texture preference test, and immunofluorescence assays at P18. HI kits exhibit altered development and allodynia in von Frey and Hargreaves and decreased sensitivity to cold. HI kits spend less time on the aversive side of the two-texture preference apparatus and more time in the center of an open field but a higher ratio of that time immobile. This is accompanied by changes in the distribution of C-fibers in the dorsal horn of the cervical and lumbar spinal cord. A principal components analysis revealed prenatal HI produces coordinated alterations across sensory and behavioral domains and multivariate phenotyping captures the overall HI phenotype more comprehensively than any single measure. Overall, HI rabbits kits exhibit altered sensory development, allodynia, anxiety-like behavior, and changes to the distribution of nociceptive afferents in the dorsal horn of the spinal cord.

neuroscience↗

bioRxiv2026

A novel machine-learning classification model detects oxidative fiber type transitions in a rabbit model of cerebral palsy

The distribution of slow-and fast-twitch fiber types in a skeletal muscle heavily influences its physiology. Muscle biopsy studies indicate atypical fiber type composition and fiber size variation in children with cerebral palsy (CP), but subjects have variable treatment history and a variety of muscles affected, so uncertainties remain. In this study, we developed a novel machine-learning classification model to perform high-throughput fiber typing of complete transverse muscle sections. Our XGBoost algorithm-based prediction model yielded a balanced accuracy score of 0.89 and a macro F1-score of 0.89, reflecting its ability to robustly predict muscle fiber type from myosin heavy chain (MyHC) isoform immunofluorescence intensities and morphological descriptors. This is the first reported fiber type classifier to consider hybrid fibers, which is a major advance, considering at least 20% of myofibers are hybrid yet they are routinely overlooked due to difficulty in their detection. We used this classification model to define fiber types of more than 7 million myofibers from flexor-extensor muscle pairs in rabbits that experienced hypoxia-ischemia (HI) injury in utero (modeling CP), and typically developing sham rabbits. We observed an oxidative fiber type shift in flexor muscles (biceps brachii and tibialis anterior) of HI rabbits at postnatal day (P)14-20 and P30-32 (weaning age). This altered fiber type composition imparts reduced contractile force and is amenable to sustained muscle activity; it may reflect chronic low-frequency motor unit activation. This work supports prior clinical reports that developmental trajectories of muscle fibers are disrupted in CP.

neuroscience↗

bioRxiv2023

Spinal motoneurons respond aberrantly to serotonin in a rabbit model of cerebral palsy

Cerebral palsy (CP) is caused by a variety of factors that damage the developing central nervous system. Impaired motor control, including muscle stiffness and spasticity, is the hallmark of spastic CP. Rabbits that experience hypoxic-ischemic (HI) injury in utero (at 70-80% gestation) are born with muscle stiffness, hyperreflexia, and, as recently discovered, increased serotonin (5-HT) in the spinal cord. To determine whether serotonergic modulation of spinal motoneurons (MNs) contributes to motor deficits, we performed ex vivo whole cell patch clamp in neonatal rabbit spinal cord slices at postnatal day (P) 0-5. HI MNs responded to application of -methyl 5-HT (a 5-HT1/5-HT2 receptor agonist) and citalopram (a selective 5-HT reuptake inhibitor) with hyperpolarization of persistent inward currents and threshold voltage for action potentials, reduced maximum firing rate, and an altered pattern of spike frequency adaptation while control MNs did not exhibit any of these responses. To further explore the differential sensitivity of MNs to 5-HT, we performed immunohistochemistry for inhibitory 5-HT1A receptors in lumbar spinal MNs at P5. Fewer HI MNs expressed the 5-HT1A receptor compared to age-matched controls. This suggests many HI MNs lack a normal mechanism of central fatigue mediated by 5-HT1A receptors. Other 5-HT receptors (including 5-HT2) are likely responsible for the robust increase in HI MN excitability. In summary, by directly exciting MNs, the increased concentration of spinal 5-HT in HI rabbits can cause MN hyperexcitability, muscle stiffness, and spasticity characteristic of CP. Therapeutic strategies that target serotonergic neuromodulation may be beneficial to individuals with CP. Key pointsO_LIAfter prenatal hypoxia-ischemia (HI), neonatal rabbits that show hypertonia are known to have higher levels of spinal serotonin C_LIO_LIWe tested responsivity of spinal motoneurons (MNs) in neonatal control and HI rabbits to serotonin using whole cell patch clamp C_LIO_LIMNs from HI rabbits showed a more robust excitatory response to serotonin than control MNs, including hyperpolarization of the persistent inward current and threshold for action potentials, larger post-inhibitory rebound, and less spike frequency adaptation C_LIO_LIBased on immunohistochemistry of lumbar MNs, fewer HI MNs express inhibitory 5HT1A receptors than control MNs, which could account for the more robust excitatory response of HI MNs. C_LIO_LIThese results suggest that after HI injury, the increased serotonin could trigger a cascade of events leading to muscle stiffness and altered motor unit development C_LI

neuroscience↗

bioRxiv2021

Enhanced nociception in a rabbit model of cerebral palsy

Spastic cerebral palsy (CP) is a movement disorder marked by hypertonia and hyperreflexia, and the most prevalent comorbidity is pain. Since spinal nociceptive afferents contribute to both the sensation of painful stimuli as well as reflex circuits involved in movement, we investigated the relationship between prenatal hypoxia-ischemia (HI) injury which can cause CP, and possible changes in spinal nociceptive circuitry. To do this, we examined nociceptive afferents and mechanical and thermal sensitivity of New Zealand White rabbit kits after prenatal HI or a sham surgical procedure. As described previously, a range of motor deficits similar to spastic CP was observed in kits born naturally after HI (40 minutes at [~]70-80% gestation). We found that HI caused an expansion of peptidergic afferents (marked by expression of calcitonin gene-related peptide; CGRP) in both the superficial and deep dorsal horn at postnatal day (P)5. Non-peptidergic nociceptive afferent arborization (labeled by isolectin B4; IB4) was unaltered in HI kits but overlap of the two populations (peptidergic and non-peptidergic nociceptors) was increased by HI. Density of glial fibrillary acidic protein (GFAP) was unchanged within spinal white matter regions important in nociceptive transmission at P5. We found that mechanical and thermal nociception was enhanced in HI kits even in the absence of motor deficits. These findings suggest that prenatal HI injury impacts spinal sensory pathways in addition to the more well-established disruptions to descending motor circuits. In conclusion, changes to spinal nociceptive circuitry could disrupt spinalreflexes and contribute to pain experienced by individuals with CP. Significance StatementPerinatal injuries that cause cerebral palsy (CP) typically involve global insults to the central nervous system and are capable of modulating development of both motor and sensory systems. Most individuals with CP experience pain, yet whether nociception is enhanced in this disorder is unexplored. Here, we demonstrate altered topographic distribution of nociceptive afferents in the spinal cord dorsal horn of neonatal rabbits that experienced hypoxic-ischemic (HI) injury in utero; these anatomical changes were associated with nocifensive behavior indicative of pain-like behaviors. Our findings suggest that CP-causative injuries alter spinal sensory pathways (not only descending motor circuits), contributing to increased pain in CP.

neuroscience↗

bioRxiv2019

Altered motoneuron properties and spinal serotonin contribute to motor deficits in a rabbit hypoxia ischemia model of cerebral palsy

Cerebral palsy (CP) is caused by a variety of factors attributed to early brain damage, resulting in permanently impaired motor control, marked by weakness and muscle stiffness. To find out if altered physiology of spinal motoneurons (MNs) could contribute to movement deficits, we performed whole cell patch clamp in neonatal rabbit spinal cord slices after developmental injury at 79% gestation. After preterm hypoxia-ischemia (HI), rabbits are born with motor deficits consistent with a spastic phenotype including hypertonia and hyperreflexia. There is a range in severity, thus kits are classified as severely affected, mildly affected, or unaffected based on modified Ashworth scores and other behavioral tests. At postnatal day (P)0-5, we recorded electrophysiological parameters of 40 MNs in transverse spinal cord slices using whole cell patch clamp. Using a multivariate analysis of neuronal parameters, we found significant differences between groups (severe, mild, unaffected and sham control MNs), age (P0 to P5) and spinal cord region (cervical to sacral). Severe HI MNs showed more sustained firing patterns, depolarized resting membrane potential, and a higher threshold for action potentials. These properties could contribute to both muscle stiffness and weakness, respectively, hallmarks of spastic CP. Interestingly altered persistent inward currents (PICs) and morphology in severe HI MNs would dampen excitability (reduced normalized PIC amplitude and increased dendritic length). In summary, changes we observed in spinal MN physiology likely contribute to severity of the phenotype including weakness and hypertonia, and therapeutic strategies for CP could target excitability of spinal MNs. Key PointsO_LIPhysiology of neonatal spinal motoneurons is altered after in utero hypoxia-ischemic injury C_LIO_LIIn motoneurons from severely affected animals there is more sustained firing (lower {Delta}I values), a depolarized resting potential, but a higher voltage threshold for action potential firing. C_LIO_LIAltered motoneuron excitability could contribute directly to muscle stiffness and spasticity in cerebral palsy. C_LI

neuroscience↗