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Dwayne W. Godwin, Nuwan C. Kurukulasuriya, W. Breckinridge Carden, Jian Mu; A new spin on the brainstem: NO redirects the data stream in the LGN. Journal of Vision 2002;2(7):580. doi: https://doi.org/10.1167/2.7.580.
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An important determinant of information flow through the lateral geniculate nucleus of the thalamus (LGN) is the cholinergic/nitrergic projection from the parabrachial brain stem (PBR). The PBR has a well-characterized cholinergic influence on information transmission, mainly through depolarization of the LGN membrane and inactivation of the low threshold calcium current (T current). A unique gaseous transmitter, nitric oxide (NO), is also released by the PBR, but its function in vision is unclear. PBR terminals are associated with glutamatergic synapses in the LGN, thus we hypothesized that NO may influence excitatory neurotransmission as well as the intrinsic membrane properties of LGN cells. Using intracellular recordings in LGN brain slices, we have studied excitatory postsynaptic potentials and currents (EPSPs/EPSCs) elicited either from the retinogeniculate (RG) or the corticothalamic (CG) pathway. Both RG and CG EPSPs are mediated by an early, non-n-methyl-d-aspartate (NMDA) component, and a later component that is sensitive to APV and mediated by NMDA receptors. NO generation within the LGN affects synaptic transmission in a unique way: RG synaptic inputs are reduced, while CG inputs are enhanced. At the same time, the T current is inhibited in a voltage-independent manner. Our findings suggest a new role for the reticular activating system in the control of visual information through the LGN. Activation of bNOS and resultant NO generation during visual processing may dynamically change the balance of information processing from a peripherally driven stream, to one that is more receptive to information carried by corticothalamic feedback loops — at a time when the relay cell membrane is in a more linear processing mode. Supported by EY11695.
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