2 KEY POINTS SUMMARY Buspirone, a partial serotoninergic agonist (5HT1A), exerts a considerable acute facilitation of spinally-mediated locomotion after a complete spinal lesion in mice. Since locomotion is associated with reflex modulation, we focused in this study on the effect of buspirone on H-reflex in acute spinal mice after decerebration and removal of anesthesia. Buspirone injection resulted in a depression of the H-reflex during the first 20 minutes followed, 40 minutes later, by an increase of the reflex. The H-reflex increase is not due to a disinhibition since buspirone had no effect on the frequency dependent depression (FDD) of the H-reflex. The use of a model of adult decerebrate mouse with complete spinal cord injury allows to establish that buspirone has a biphasic effect on the H-reflex and that the inhibitory action on sensory information concurs with an excitatory action on locomotion.3 ABSTRACT Pharmacological treatment facilitating locomotor expression also modulates reflex expression through the re-arrangement of spinal networks. Buspirone, a partial serotonin receptor agonist (5-HT1A), was recently shown to facilitate and even trigger locomotor movements in mice after complete spinal lesion (Tx). Here, we studied its effect on the Hreflex after acute Tx in adult mice. To avoid possible impacts of anesthetics on H-reflex depression, experiments were performed after decerebration in un-anesthetized mice (N=13).The H-reflex in plantar muscles of the hind-paw was recorded after tibial nerve stimulation 2 h after Tx at the 8 th thoracic vertebrae. Average H/M ratio was compared before and every 10 min after buspirone (8 mg/kg, i.p.) for 60 min. Frequency-dependent depression (FDD)of the H-reflex was assessed before and 50 min after buspirone. Before buspirone, a stable H-reflex could be elicited in acute spinal mice and FDD of the H-reflex was observed at 5Hz (68%) and 10Hz (70%) relative to 0.2Hz. After buspirone, the H/M ratio was initially significantly decreased to 69% of pre-treatment. It then increased significantly 30 to 60 min after exposure to buspirone, reaching 170% 60 min after injection. FDD 50 min after buspirone was not significantly different that FDD without treatment. Altogether results suggest that the reported pro-locomotor effect of buspirone occurs at a time where there is a reflex depression followed by a second phase marked by enhancement of reflex excitability, denoting functional inhibitory control. Abbreviations: 5-HT: 5-Hydroxytryptamine; 5-HT1A: 1A subunit in 5-Hydroxytryptamine receptor; 8-OHDPAT: 8-Hydroxy-2-DI-n-Propylamino-Tetraline; CPG Central Pattern Generator; EMG: electromyographic; FDD: Frequency Dependent Depression; GABA: Gamma-Aminobutyric-Acid; TASK-1 acid-sensitiv-K-1; Tx: complete transection. Antri M, Mouffle C, Orsal D, and Barthe J. 5-HT 1A receptors are involved in short-and long-term processes responsible for 5-HT-induced locomotor function recovery in chronic spinal rat. Eur J Neurosci 18: 1963-1972, 2003. Barbeau H and Rossignol S. Re...
Pharmacological treatment facilitating locomotor expression will also have some effects on reflex expression through the modulation of spinal circuitry. Buspirone, a partial serotonin receptor agonist (5-HT 1A), was recently shown to facilitate and even trigger locomotor movements in mice after complete spinal lesion (Tx). Here, we studied its effect on the H-reflex after acute Tx in adult mice. To avoid possible impacts of anesthetics on H-reflex depression, experiments were performed after decerebration in un-anesthetized mice (N = 20). The H-reflex in plantar muscles of the hind paw was recorded after tibial nerve stimulation 2 h after Tx at the 8th thoracic vertebrae and was compared before and every 10 min after buspirone (8 mg/kg, i.p.) for 60 min (N = 8). Frequency-dependent depression (FDD) of the H-reflex was assessed before and 60 min after buspirone. Before buspirone, a stable H-reflex could be elicited in acute spinal mice and FDD of the H-reflex was observed at 5 and 10 Hz relative to 0.2 Hz, FDD was still present 60 min after buspirone. Early after buspirone, the H-reflex was significantly decreased to 69% of pre-treatment, it then increased significantly 30-60 min after treatment, reaching 170% 60 min after injection. This effect was not observed in a control group (saline, N = 5) and was blocked when a 5-HT 1A antagonist (NAD-299) was administered with buspirone (N = 7). Altogether results suggest that the reported pro-locomotor effect of buspirone occurs at a time where there is a 5-HT 1A receptors mediated reflex depression followed by a second phase marked by enhancement of reflex excitability.
BACKGROUND: There is no non-invasive in vivo method to assess intervertebral kinematics. Current kinematics models are based on in vitro bone reconstructions from computed tomography (CT)-scan imaging, fluoroscopy and MRIs, which are either expensive or deleterious for human tissues. Musculoskeletal ultrasound is an accessible, easy to use and cost-effective device that allows high-resolution, real-time imaging of bone structure. OBJECTIVE: The aim of this preliminary study was to compare the concordance of 3D bone modeling of lumbar vertebrae between CT-scan and ultrasound imaging and to study the intra and inter-reliability of distances measured on 3D ultrasound bone models. METHODS: CT-scan, ultrasound, and in situ data of five lumbar vertebrae from the same human specimen were used. All vertebrae were scanned by tomography and a new musculoskeletal ultrasound procedure. Then, 3D bone modeling was created from both CT-scan and ultrasound image data set. Distances between anatomical bones landmarks were measured on the 3D models and compared to in situ measurements. We observed that all distances were included within the limit of agreement between the three methods of measurements (3D CT-scan, 3D MSU and in situ) with a good intra- and inter-reliability of 3D ultrasound measurements of 0.97 and 0.82, respectively. Based on the mean of mean differences between methods, we observed for all distances, ultrasound overestimated distances of 0.44 ± 0.63 mm compared to CT-scan, ultrasound underestimated distances of 0.39 ± 0.48 mm compared to in situ measurements and CT-scan underestimated distances of 0.93 ± 0.55 mm compared to in situ measurements. CONCLUSIONS: Three-dimensional modeling from ultrasound imaging is similar in comparison to 3D bone modeling from CT-scan imaging with a good intra and inter reliability.
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