Shaw, Philip John; (1998) Nitric oxide and glutathione as modulators of thalamic sensory neurotransmission in the rat. Masters thesis (M.Phil), UCL (University College London).

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Abstract

The ventrobasal complex of the thalamus (VB) and the dorsal lateral geniculate nucleus (dLGN) are the thalamic nuclei that carry information regarding somatosensory and visual modalities, respectively. Thalamic sensory nuclei do not, however, passively convey information to the cerebral cortex; rather, they are capable of complex modulations of the pattern of neuronal firing. The intercellular messenger nitric oxide has a number of postulated roles in synaptic transmission in the CNS. There is accumulating evidence that nitric oxide is present in the thalamus and that it has a role in sensory neurotransmission. This was designed to investigate the involvement of nitric oxide in neurotransmission in VB and dLGN, using a variety of pharmacological tools. Using an in vivo rat preparation, drugs were applied to relay neurones by iontophoresis; by combining this technique with single cell extracellular recording, it was possible to determine the effects of drugs which interact with the nitric oxide system. The results indicate that nitric oxide donors have a facilitatory action both in VB and dLGN, supporting previous work which suggests that nitric oxide has an excitatory action in the thalamus. Similarly, evidence is presented which supports the suggestion that thalamic nitric oxide exerts its effects via stimulation of guanylate cyclase to increase the intracellular concentration of cGMP. Additionally, the effects of glutathione were tested using the same experimental protocols; the results indicate that both reduced and oxidised glutathione have an inhibitory action in VB and dLGN. Given that the thalamic sensory nuclei have an important role in arousal, the pharmacology of agents which modulate the responsiveness of relay neurones is of great significance. The evidence presented supports the suggestion that nitric oxide has a facilitatory function in the gating of sensory information in the thalamus, and proposes that glutathione has an inhibitory role in the same physiological processes.

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