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Department of Molecular and Integrative Physiology, University of Illinois; Department of Pharmacology, University of Illinois College of Medicine; and Beckman Institute, University of Illinois, Urbana, Illinois
Submitted 6 June 2005; accepted in final form 9 August 2005
The excitability of relay neurons in the dorsal geniculate nucleus (dLGN) can be altered by a variety of neuromodulators. The dLGN receives substantial dopaminergic input from the brain stem, and this innervation may play a crucial role in the gating of visual information from the retina to visual neocortex. In this study, we investigated the action of dopamine on identified dLGN neurons using whole cell recording techniques. Dopamine (2200 µM) produced a membrane depolarization in >95% of relay neurons tested but did not alter excitability of dLGN interneurons. The D1-like dopamine receptor agonist SKF38393 (250 µM) produced a similar depolarization in dLGN relay neurons. However, the D2-like receptor agonists, bromocriptine (2550 µM) and PPHT (150 µM), did not alter the membrane potential of relay neurons. SCH23390 (510 µM), a D1-like receptor antagonist, attenuated the depolarizing actions of both dopamine and SKF38393. Furthermore, the excitatory actions of dopamine and SKF38393 were attenuated by ZD7288, a specific antagonist for the hyperpolarization activated mixed cation current, Ih. Our data suggest that dopamine, acting via D1-like receptors, activates Ih leading to a membrane depolarization. Through the modulation of dLGN neuronal excitability, ascending and descending activating systems may not only control the state of the thalamus such as the transition from slow-wave sleep to waking but also regulate the efficacy of information transfer during waking states.
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