Journal of neurophysiology
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The contribution of the zona incerta (ZI) of the thalamus on spike-wave discharges (SWDs) was investigated. Chronic recordings of bilateral cortices, bilateral vibrissa muscle, and unilateral ZI were performed in Long-Evans rats to examine the functional role of SWDs. Rhythmic ZI activity appeared at the beginning of SWD and was accompanied by higher-oscillation frequencies and larger spike magnitudes. ⋯ A unilateral ZI lesion resulted in a significant reduction of 7- to 12-Hz power of both the ipsilateral cortical and contralateral vibrissae muscle activities during SWDs. Intraincertal microinfusion of muscimol showed a significant inhibition on SWDs. Our present data suggest that the ZI actively modulates the SWD magnitude and WT behavior.
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Purkinje cells have specialized intrinsic ionic conductances that generate high-frequency action potentials. Disruptions of their Ca or Ca-activated K (KCa) currents correlate with altered firing patterns in vitro and impaired motor behavior in vivo. To examine the properties of somatic KCa currents, we recorded voltage-clamped KCa currents in Purkinje cell bodies isolated from postnatal day 17-21 mouse cerebellum. ⋯ In current clamp, EBIO slowed spiking, especially during depolarizing current injections. The two components of BK current in Purkinje somata likely contribute differently to spike repolarization and firing rate. Moreover, augmentation of BK current may partially underlie the action of EBIO and chlorzoxazone to alleviate disrupted Purkinje cell firing associated with genetic ataxias.
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Corneal primary afferent neurons that respond to drying of the ocular surface have been previously characterized and found to respond to innocuous cooling, menthol, and hyperosmotic stimuli. The purpose of the present study was to examine the receptive field properties of second-order neurons in the trigeminal nucleus that respond to drying of the ocular surface. Single-unit electrophysiological recordings were performed in anesthetized rats, and dry-responsive corneal units were isolated in the brain stem at the transition zone between the spinal trigeminal subnucleus caudalis and subnucleus interpolaris. ⋯ Furthermore, neurons that were activated by low pH had a significantly lower response to cooling and menthol. These results indicate that dry-responsive neurons recorded in the trigeminal nucleus receive input from cold, sensitive primary afferent neurons, with a subset of these neurons receiving input from corneal primary afferent neurons sensitive to acid and noxious heat. It is proposed that acid-insensitive corneal neurons represent a labeled line for lacrimation in response to evaporation of tears from the ocular surface, whereas acid-sensitive neurons are involved in tearing, elicited by damaging or potentially damaging stimuli.