In vivo recording of postsynaptic potentials and low threshold spikes in W cells of the cat's lateral geniculate nucleus.
We obtained good intracellular recording from 5 W cells in the C-laminae of the cat's lateral geniculate nucleus. The recordings were made from an anesthetized and paralyzed in vivo preparation. We found a consistent pattern for the postsynaptic potentials evoked from activation of the optic chiasm: first was an IPSP followed by an EPSP. This is very different from the pattern seen in X and Y cells, for which an EPSP always appears first and is then followed by an IPSP. We interpret the pattern for W cells as follows. The initial IPSP is disynaptic; this involves retinogeniculate conduction over very fast Y axons and a relay through an interneuron. The EPSP is monosynaptic, reflecting retinogeniculate conduction over very slow W axons. A possible implication for this is that activity over the Y pathway may generally inhibit geniculate W cells before these W cells can be excited by their retinal afferents. Finally, we elicited from each of these W cells voltage-dependent, low threshold spikes, which are very similar to those displayed by X and Y cells. These spikes can interrupt normal retinogeniculate transmission, and they are prevented by maintaining relatively depolarized membrane potentials.
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Department of Neurobiology, State University of New York, Stony Brook 11794-5230.
Sherman
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D000818:Animals; D002415:Cats; D004558:Electric Stimulation / Q000379:methods; D004594:Electrophysiology / Q000379:methods; D005071:Evoked Potentials; D005829:Geniculate Bodies / Q000166:cytology / Q000502:physiology*; D008959:Models, Neurological; D009897:Optic Chiasm / Q000502:physiology; D013569:Synapses / Q000502:physiology*