In the rat, some findings have been taken to suggest the existence of monosynaptic corticomotoneuronal (CM) connections. Because this connection is believed to be largely responsible for the ability to make independent digit movements in primates and man, it has been inferred that the monosynaptic CM connection in the rat is likewise important for skilled prehension. Comparison of intra- and extracellular recordings from forelimb motoneurons in anesthetized rats, revealed no monosynaptic CM excitatory postsynaptic potentials (EPSPs). The fastest descending excitation in forelimb motoneurons was disynaptically mediated via a corticoreticulospinal pathway and slowly conducted excitation via corticospinal fibers and segmental interneurons. The findings stress the importance of di- and trisynaptic excitatory corticofugal pathways to forelimb motoneurons in the control of skillful digit movements.

Progression of degeneration of cervical spine on MRI was frequently observed during 10-year period, with development of symptoms in 34% of subjects. No factor related to progression of degeneration of cervical spine was identified except for age.

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Alstermark, Bror and Jun Ogawa. In vivo recordings of bulbospinal excitation in adult mouse forelimb motoneurons. J Neurophysiol 92: 1958 -1962. First published April 14, 2004 10.1152/jn.00092.2004. Here we report on pyramidal and reticulospinal excitation in forelimb motoneurons in the adult mouse using intracellular recordings in vivo. The results have been obtained in BALB/C mice, which were anesthetized with midazolam fentanyl/fluanison. In contrast to the rat, only weak and infrequent pyramidal excitation could be evoked with a minimal trisynaptic linkage. Disynaptic reticulospinal excitation could always be evoked, as well as monosynaptic excitation from the medial longitudinal fasciculus. The results suggest that the reticulospinal pathway in the mouse is important in voluntary motor control of the forelimbs and that the role of the corticospinal tract might be different in mouse compared with rat. Our study provides an opening for studying the effect of genetic manipulation on specified descending systems in the mouse in vivo. I N T R O D U C T I O NThe mouse has become a particularly important model for physiological investigations after the mouse genome project (Mouse Genome Sequencing Consortium 2002), and there is a dramatic increase in the use of transgenic animals for exploring the functional role of specific genes. This is also true for the brain, where much work is devoted to developmental control, diseases, and in vitro studies of neuronal properties in neonates. A major difficulty for neurophysiological investigations has been to perform intracellular recordings from motoneurons in vivo in the adult mouse. Since the work by Kuno and colleagues (Huizar et al. 1975;Kuno 1976) on the electrophysiological properties of spinal motoneurons in normal and dystrophic mice, no publications using intracellular recordings in vivo can be found in PubMed.We have recently analyzed pyramidal excitation in the adult rat using intracellular recording from forelimb motoneurons (Alstermark et al. 2004), and the work by Kuno and colleagues inspired us to attempt a similar analysis in the adult mouse. It will be shown that pyramidal stimulation evokes surprisingly weak excitation in forelimb motoneurons via the corticospinal pathway (different to rat) and that strong excitation is mediated via a fast reticulospinal pathway (similar to rat). The results suggest a partly different role in motor control of the corticospinal tract in mouse and rat. M E T H O D S PreparationThe results were obtained from 15 mice (5 females and 10 males; BALB/C, Mollegaard), with body weights of 24 -30 g and age of 2-4 mo. The animals were anesthetized with a mixture (initial dose, 0.15 ml/30 g ip supplemented with doses of 0.02 ml, maximal dose 0.25 ml) of midazolam (2.5 mg/ml) and fentanyl/fluanison (5.1 mg/ml). Atropin (total dose, 0.5 mg) and decadrone (total dose, 0.4 mg) were always given (subcutaneously) just after anesthesia. Ephedrine was given in doses of 0.1 mg when pCO 2 decreased below 1% for Ͼ5 min (intraperitoneal initial ...

There have been few studies that investigated and clarified the relationships between progression of degenerative changes and sagittal alignment of the cervical spine. The objective of the study was to longitudinally evaluate the relationships among progression of degenerative changes of the cervical spine with age, the development of clinical symptoms and sagittal alignment of the cervical spine in healthy subjects. Out of 497 symptom-free volunteers who underwent MRI and plain radiography of the cervical spine between 1994 and 1996, 113 subjects (45 males and 68 females) who responded to our contacts were enrolled. All subjects underwent another MRI at an average of 11.3 years after the initial study. Their mean age at the time of the initial imaging was 36.6 ± 14.5 years (11-65 years). The items evaluated on MRI were (1) decrease in signal intensity of the intervertebral disks, (2) posterior disk protrusion, and (3) disk space narrowing. Each item was evaluated using a numerical grading system. The subjects were divided into four groups according to the age and sagittal alignment of the cervical spine, i.e., subjects under or over the age of 40 years, and subjects with the lordosis or non-lordosis type of sagittal alignment of the cervical spine. -009-1095-5 During the 10-year period, progression of decrease in signal intensity of the disk, posterior disk protrusion, and disk space narrowing were recognized in 64.6, 65.5, and 28.3% of the subjects, respectively. Progression of posterior disk protrusion was significantly more frequent in subjects over 40 years of age with non-lordosis type of sagittal alignment. Logistic regression analysis revealed that stiff shoulder was closely correlated with females (P = 0.001), and that numbness of the upper extremity was closely correlated with age (P = 0.030) and male (P = 0.038). However, no significant correlation between the sagittal alignment of the cervical spine and clinical symptoms was detected. Sagittal alignment of the cervical spine had some impact on the progression of degenerative changes of the cervical spine with aging; however, it had no correlation with the occurrence of future clinical symptoms.123 Eur Spine J (2009) 18:1644-1651 DOI 10.1007/s00586