Abstract
A patch-clamp recording in slices generated from the brain or the spinal cord has facilitated the exploration of neuronal circuits and the molecular mechanisms underlying neurological disorders. However, the rodents that are used to generate the spinal cord slices in previous studies involving a patch-clamp recording have been limited to those in the juvenile or adolescent stage. Here, we applied an N-methyl-D-glucamine HCl (NMDG-HCl) solution that enabled the patch-clamp recordings to be performed on the superficial dorsal horn neurons in the slices derived from middle-aged rats. The success rate of stable recordings from substantia gelatinosa (SG) neurons was 34.6% (90/260). When stimulated with long current pulses, 43.3% (39/90) of the neurons presented a tonic-firing pattern, which was considered to represent γ-aminobutyric acid-ergic (GABAergic) signals. Presumptive glutamatergic neurons presented 38.9% (35/90) delayed and 8.3% (7/90) single-spike patterns. The intrinsic membrane properties of both the neuron types were similar but delayed (glutamatergic) neurons appeared to be more excitable as indicated by the decreased latency and rheobase values of the action potential compared with those of tonic (GABAergic) neurons. Furthermore, the glutamatergic neurons were integrated, which receive more excitatory synaptic transmission. We demonstrated that the NMDG-HCl cutting solution could be used to prepare the spinal cord slices of middle-aged rodents for the patch-clamp recording. In combination with other techniques, this preparation method might permit the further study of the functions of the spinal cord in the pathological processes that occur in aging-associated diseases.
Highlights
Whole-cell patch-clamp recordings of the spinal cord slices represent an essential experimental system in neuroscience, which has enabled detailed studies of the neuronal architecture, spinal cord circuits, and their functions in the processes that are associated with both the physiological and pathological conditions (Konnerth, 1990)
Several attempts have been made to perform the electrophysiological recordings from the neurons in the preparation of the spinal cord slices made from adult animals
Ataka demonstrated that baclofen inhibits the glutamatergic transmission evoked by C-afferents more effectively than those evoked by Aδ-afferents using whole-cell patch-clamp recordings on the spinal cord slices obtained from 7–8-week-old Sprague Dawley rats (Ataka et al, 2000)
Summary
Whole-cell patch-clamp recordings of the spinal cord slices represent an essential experimental system in neuroscience, which has enabled detailed studies of the neuronal architecture, spinal cord circuits, and their functions in the processes that are associated with both the physiological and pathological conditions (Konnerth, 1990). Several researchers have studied primary afferent axonal projections and local neuronal circuits in the spinal cord (Brumovsky et al, 2006; Uta et al, 2010). These cellular and synaptic features of SG neurons are typically performed in the spinal cord slices obtained from newborn or young rodents; the features of the spinal cord neurons of middle-aged and older rodents remain unknown. Since the current spinal cord slice preparation procedures are not suitable for aging rodents, the electrophysiological properties of SG neurons have not been evaluated by the in vitro recordings from the animal models of these diseases
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