NORADRENERGIC INFLUENCE ON TONIC FIRING IN TRIGEMINAL GANGLION NEURONS

Adrenoreceptors play a key role in sympathetic influences on sensory neurons in normal and neuropathic conditions. We studied noradrenaline action on tonic firing in cultured rat trigeminal ganglion neurons. In a majority of the neurons (68%), Noradrenaline application had no marked effect on the firing properties. The rest of the cells (32%) were highly sensitive to noradrenaline action; they lost the ability to tonic firing and single action potential parameters significantly changed. It was established that NA-induced action on the firing is mainly due to the activation kinetics slowing of voltage-gated calcium channels. The data suggest a possibility of differential sympatho-sensory interaction in the trigeminal pathways.