AGE-RELATED CHANGE IN TRIGEMINAL GANGLION EXCITABILITY

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Age is a risk factor for neuropathic pain such as trigeminal neuralgia. Trigeminal neuralgia is a severe, recurrent (episodic, but otherwise chronic) neuropathic facial pain syndrome that is rarely observed in children or young adults. The incidence of trigeminal neuralgia increases substantially with advancing age. While vascular compression of the trigeminal nerve root appears to be the main element in the etiology of trigeminal neuralgia, an age-related change in the intrinsic electrical properties of trigeminal ganglion neurons could be a significant contributing factor. Rise in the amplitude of (normally sub-threshold) membrane oscillations in the somata would facilitate abnormal action potential discharge in trigeminal ganglion neurons. The goal of this pilot research proposal is to determine if advanced age is associated with an increase in the background electrical activity of neuronal cell bodies in the trigeminal ganglion. The project will examine trigeminal ganglion neurons from 6-, 12-, 18-, and 24-month old rats. Tight-seal, whole-cell (patch-clamp) techniques will be used in both current- and voltage-clamp recording mode. Current-clamp measurements will record the excursions in membrane potential (i.e., fluctuations, oscillations, and action potential discharge) that occur either spontaneously or in response to current injection. Voltage-clamp recordings will measure the effect of aging on the time course and amplitude of inward and outward membrane currents. The experiments will contribute to a better understanding of the factors which may contribute to the age-related increase in the incidence of trigeminal neuralgia and other types of oro-facial neuropathic pain.