Journal of neurophysiology
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Using patch-clamp techniques, we studied the plasticity of acid-sensing ion channels (ASIC) and transient receptor potential V1 (TRPV1) channel function in dorsal root ganglia (DRG) neurons retrogradely labeled from the bladder. Saline (control) or cyclophosphamide (CYP) was given intraperitoneally on days 1, 3, and 5. On day 6, lumbosacral (LS, L6-S2) or thoracolumbar (TL, T13-L2) DRG were removed and dissociated. ⋯ Correspondingly, heat triggered current at a significantly lower temperature in bladder neurons from CYP-treated rats compared with controls. These results reveal that cystitis differentially affects TRPV1- and ASIC-mediated currents in both bladder sensory pathways. Acidification of the bladder wall during inflammation may contribute to changes in nociceptive transmission mediated through the TRPV1 receptor, suggesting a role for TRPV1 in hypersensitivity associated with cystitis.
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The brain-derived neurotrophic factor gene (BDNF) is one of many genes thought to influence neuronal survival, synaptic plasticity, and neurogenesis. A common single nucleotide polymorphism (SNP) of the BDNF gene due to valine-to-methionine substitution at codon 66 (BDNF Val66Met) in the normal population has been associated with complex neuronal phenotype, including differences in brain morphology, episodic memory, or cortical plasticity following brain stimulation and is believed to influence synaptic changes following motor learning task. However, the effect of this polymorphism on spinal plasticity remains largely unknown. ⋯ Anodal tsDCS induced a progressive leftward shift of recruitment curve of the H reflex during the stimulation that persisted for at least 15 min after current offset in Val/Val individuals. In contrast, this shift was not observed in Met allele carriers. Our findings demonstrate for the first time that the BDNF Val66Met genotype impacts spinal plasticity in humans, as assessed by tsDCS, and may be one factor influencing the natural response of the spinal cord to injury or disease.
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After a spinal hemisection at thoracic level in cats, the paretic hindlimb progressively recovers locomotion without treadmill training but asymmetries between hindlimbs persist for several weeks and can be seen even after a further complete spinal transection at T13. To promote optimal locomotor recovery after hemisection, such asymmetrical changes need to be corrected. In the present study we determined if the locomotor deficits induced by a spinal hemisection can be corrected by locomotor training and, if so, whether the spinal stepping after the complete spinal cord transection is also more symmetrical. ⋯ Moreover, after the complete spinal lesion was performed, all the trained cats reexpressed bilateral and symmetrical hindlimb locomotion within 24 h. By contrast, the locomotor pattern of the untrained cats remained asymmetrical, and the hindlimb on the side of the hemisection was still deficient. This study highlights the beneficial role of locomotor training in facilitating bilateral and symmetrical functional plastic changes within the spinal circuitry and in promoting locomotor recovery after an incomplete spinal cord injury.
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Ankle clonus is common after spinal cord injury (SCI) and is attributed to loss of supraspinally mediated inhibition of soleus stretch reflexes and maladaptive reorganization of spinal reflex pathways. The maladaptive reorganization underlying ankle clonus is associated with other abnormalities, such as coactivation and reciprocal facilitation of tibialis anterior (TA) and soleus (SOL), which contribute to impaired walking ability in individuals with motor-incomplete SCI. Operant conditioning can increase muscle activation and decrease stretch reflexes in individuals with SCI. ⋯ TA↑ decreased plantar flexor reflex threshold angle (-4.33°) and DF active range-of-motion angle (-4.32°) and increased LEMS of DF (+0.8 points), total LEMS of the training leg (+2.2 points), and nontraining leg (+0.8 points), and increased walking foot clearance (+ 4.8 mm) and distance (+12.09 m). SOL↓ decreased SOL-to-TA coactivation ratio (-0.21), increased nontraining leg LEMS (+1.8 points), walking speed (+0.02 m/s), and distance (+6.25 m). In sum, we found increased voluntary control associated with TA↑ outcomes and decreased reflex excitability associated with SOL↓ outcomes.
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The development of auditory temporal processing is important for processing complex sounds as well as for acquiring reading and language skills. Neuronal properties and sound processing change dramatically in auditory cortex neurons after the onset of hearing. However, the development of the auditory thalamus or medial geniculate body (MGB) has not been well studied over this critical time window. ⋯ GABAA and GABAB inhibitory postsynaptic potentials were present at all ages and were similar in amplitude. Inhibitory postsynaptic potentials became faster to single shocks, showed less depression to train stimuli at 5 and 10 Hz, and were overall more efficacious in controlling excitability with age. Overall, IC-MGB inhibition becomes faster and more precise during a time period of rapid changes across the auditory system due to the codevelopment of membrane properties and synaptic properties.