The nature of the excitatory transmitter mediating X and Y cell inputs to the cat dorsal lateral geniculate nucleus

Abstract

4. GDEE was relatively ineffective in blocking either agonist responses or the visual response and only produced a significant reduction in either at dose levels that caused a similar depression in the response to acetylcholine. DAP would block responses to DLH but produced no significant effect on the visual response or the responses to glutamate and acetylcholine.5. The cholinergic antagonists atropine and dihydro-fi-erythroidine (DHflE) blocked responses to acetylcholine without significantly reducing either visual driving or the response to DLH.6. The effects were the same for X and Y cells in the dorsal lateral geniculate nucleus (dLGN). There was also no distinctions between 'on' and 'off' centre types of each of the two groups.7. The significance of these results is discussed. It is argued that they reintroduce the possibility that either L-aspartate, L-glutamate or a similar substance may be the transmitter mediating the optic nerve input to the cat dLGN.

Enhanced activation of NMDA receptor responses at the immature retinogeniculate synapse

“…Analogy with other systems suggests that synaptic plasticity in retinothalamic connections depends on activation of NMDA receptors (Constantine-Paton et al, 1990). Some evidence has been obtained for this possibility: both NMDA and non-NMDA glutamate receptors contribute to retinogeniculate transmission in the adult cat and ferret LGNd (Kemp and Sillito, 1982;Scharfman et al, 1990;Esguerra et al, 1992), blockade ofNMDA receptors on LGNd cells prevents the formation of "On" and "Off' sublamination (Hahm et al,199 1) and recent experiments have indicated that plasticity at the retinogeniculate synapse may involve activation of NMDA receptors (Mooney et al, 1993).…”

Comparison of s‐ and κ‐ opiate receptor ligands as excitatory amino acid antagonists

“…That NMA receptors mediate some synaptic excitations appears to be well established (Watkins & Evans, 1981); furthermore such receptors seem to be important in some of the pathways that transfer information into, within and out of the cerebral cortices (e.g. Stone, 1979;Martin, 1980;Kemp & Sillito, 1982;Hicks & Guedes, 1983). It seems likely then that drugs which interfere with information transfer at such sites will produce abnormalities of perception and behaviour, a prediction consistent with the psychotomimetic effects produced in man by both dissociative anaesthetics and benzomorphans with actions at a-receptors (see Introduction).…”

Proceedings of the Physiological Society, 30‐31 March 1990,University College London Meeting: Communications

“…Whether facilitated or inhibited by drug application, the majority of the cells clearly did not show a reduction in response selectivity. (Kemp & Sillito, 1982;Sillito et al 1990 a, b). It is now clear that in vitro responses mediated via the NMDA receptor (Johnson & Ascher, 1987;Thomson et al 1989) are greatly enhanced via an action of glycine at a strychnine-insensitive glycine receptor.…”

“…gallamine triethiodide) cats prepared and maintained as previously described (Kemp & Sillito, 1982). Seven barrelled micropipettes were used for extracellular recording of single-unit activity and ionophoretic application of drugs.…”