Modulation of lateral geniculate neurone excitability by noradrenaline microiontophoresis or locus coeruleus stimulation

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Abstract
Modulation of the rat lateral geniculate nucleus [LGNd] neuron excitability by noradrenaline [NA, norepinephrine] microiontophoresis or locus coeruleus [LC] stimulation was studied. Microiontophoretic NA mimicked the ability of LC stimulation to enhance the synaptic excitation of LGNd neurons. Since NA and LC stimulation did not activate LGNd neurons in the absence of synaptic or glutamate-induced excitation, both appeared to act through a neuromodulatory mechanism. The postsynaptic .alpha.-andrenoceptor antagonist WB-4101 [2-([2'',6''-dimethoxy]phenoxyethylamino)methylbenzodioxan HCI] blocked the facilitation produced by locally applied NA and by coeruleo-geniculate pathway stimulation providing evidence for pharmacologic identity of the 2 effects.