12 research outputs found
Contribution du cortex moteur et des afférences cutanées dans le contrôle et la plasticité de la locomotion chez le chat
Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal
Motor Cortical Modulation of Cutaneous Reflex Responses in the Hindlimb of the Intact Cat
Changes in Corticospinal Efficacy Contribute to the Locomotor Plasticity Observed After Unilateral Cutaneous Denervation of the Hindpaw in the Cat
Distinct dampening effects of progesterone on the activity of nucleus tractus solitarii neurons in rat pups
Progesterone is known to stimulate breathing, but its actions on the respiratory control system
have received limited attention. We addressed this issue at the cellular level by testing the
hypothesis that progesterone augments excitatory currents at the level of the nucleus tractus
solitarii (NTS). Medullary slices from juvenile male rats (14–17 days of age) containing the
commissural region of the NTS (NTScom) were incubated with progesterone (1 M) or vehicle
(0.004% DMSO) for 60 min. We performed whole-cell voltage-clamp recordings of spontaneous
excitatory postsynaptic currents (EPSCs) in the NTScom and determined membrane properties
by applying depolarizing current steps. In comparison to vehicle-treated cells, progesterone
exposure attenuates the firing frequency response to current injection and reduces the EPSC
amplitude without modifying the EPSC frequency or the basal membrane properties. These
data do not support our hypothesis, because they indicate that incubation with progesterone
attenuates intrinsic action potential generation and inhibits excitatory synaptic inputs in the
NTS. Given that these results are more in line with the protective effect of progesterone against
excitotoxicity resulting from various insults, we propose that progesterone acts via inhibition of
ionic flux
Heterozygous Mutant Mice Have a Subtle Locomotor Phenotype
Axon guidance receptors such as deleted in colorectal cancer (DCC) contribute to the normal formation of neural circuits, and their mutations can be associated with neural defects. In humans, heterozygous mutations in have been linked to congenital mirror movements, which are involuntary movements on one side of the body that mirror voluntary movements of the opposite side. In mice, obvious hopping phenotypes have been reported for bi-allelic mutations, while heterozygous mutants have not been closely examined. We hypothesized that a detailed characterization of heterozygous mice may reveal impaired corticospinal and spinal functions. Anterograde tracing of the motor cortex revealed a normally projecting corticospinal tract, intracortical microstimulation (ICMS) evoked normal contralateral motor responses, and behavioral tests showed normal skilled forelimb coordination. Gait analyses also showed a normal locomotor pattern and rhythm in adult mice during treadmill locomotion, except for a decreased occurrence of out-of-phase walk and an increased duty cycle of the stance phase at slow walking speed. Neonatal isolated spinal cords had normal left-right and flexor-extensor coupling, along with normal locomotor pattern and rhythm, except for an increase in the flexor-related motoneuronal output. Although mice do not exhibit any obvious bilateral impairments like those in humans, they exhibit subtle motor deficits during neonatal and adult locomotion