Abstract
Connections between the vestibular system and the basal ganglia have been postulated since the early 20th century. However, the results of electrophysiological studies investigating neuronal responses to electrical stimulation of the vestibular system have been inconsistent. The aim of this study was to investigate the effects of electrical stimulation of the vestibular labyrinth on single neuron activity and c‐Fos expression in the rat striatum. We used electrical stimulation of the vestibular labyrinth (various intensities delivered to the round window) to examine the electrophysiological response of striatal neurons and c‐Fos expression. From 507 single neurons recorded (n = 20 rats), no vestibular‐responsive neuron was found at 1× and 2× the nystagmus threshold; however, 6 neurons were found at 3× the threshold. These neurons were found bilaterally, with a response latency of ~50 msec from the end of the stimulus. For the c‐Fos study, the number of neurons expressing c‐Fos was quantified using stereological methods. Stimulation at 2× the threshold for nystagmus (n = 5 rats) resulted in a significant decrease in the number of neurons expressing c‐Fos in the bilateral striatum compared to both the sham control group (n = 5) and the lower stimulus intensity group (n = 5) (P ≤ 0.0001 for both). The results of this study demonstrate that: (1) some single striatal neurons respond to electrical vestibular stimulation, however, these responses are circumscribed and infrequent; (2) electrical stimulation of the vestibular labyrinth results in a decrease in the number of striatal neurons expressing c‐Fos, in a current‐dependent manner.
Highlights
Since the first half of the 20th century, it has been hypothesized that the vestibular system might transmit sensory information to the striatum (e.g., Muskens 1914, 1922)
The objectives of this study were to determine: (1) whether single neurons in the striatum would respond to electrical stimulation of the peripheral vestibular system in urethane-anesthetized rats; (2) whether electrical stimulation of the peripheral vestibular system in rat resulted in a change in the number of cells expressing cFos, using the immediate early gene protein c-Fos as a marker of cellular activation in the striatum (Sheng and Greenberg 1990)
The results of this study have demonstrated that electrical stimulation of the vestibular labyrinth can evoke responses in single striatal neurons, albeit in a very small and circumscribed population
Summary
Since the first half of the 20th century, it has been hypothesized that the vestibular system might transmit sensory information to the striatum (e.g., Muskens 1914, 1922). It seemed self-evident that a sensory system that detects angular and linear acceleration of the head during self-motion (see Cullen 2012 for a review), might provide useful sensory data to a CNS structure concerned with the control of voluntary movement (see Stiles and Smith 2015 for a review).
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