The Role Of Dopamine And Other Neuromodulators As Light Signals In The Inner Retina: A Link To Night Blindness Disorders
Funder
National Health and Medical Research Council
Funding Amount
$250,250.00
Summary
Although most human activities can be performed at night as efficiently as during daytime due to the use of artificial light, normal function of the circuits underlying night vision is critical. For example, when driving at night in a poorly illuminated road where the region illuminated by the headlights is processed by the cone circuit that serves daylight in the retina whilst the peripheral areas are processed by the rod driven nighttime circuit. Impairment of night vision and of the dark-ligh ....Although most human activities can be performed at night as efficiently as during daytime due to the use of artificial light, normal function of the circuits underlying night vision is critical. For example, when driving at night in a poorly illuminated road where the region illuminated by the headlights is processed by the cone circuit that serves daylight in the retina whilst the peripheral areas are processed by the rod driven nighttime circuit. Impairment of night vision and of the dark-light switch can have fatal consequences. Night blindness is a symptom characterised by reduced vision in the dark and slow adaptation to dim light. Some congenital night blindness disorders are caused by mutations in the photoreceptor calcium channels which mediate signal transmission. Additionally, patients treated with neuroleptics, a group of drugs which affect the dopaminergic system, suffer night vision disorders. Dopamine acts as a light signal in the retina. AII amacrine cells are pivotal neurones for night vision segregating two channels (ON and OFF) which convey visual information. AII cells are modulated by dopamine and thus, represent interesting targets to study the role of dopamine in the dark-light switch. Much is know about the action of dopamine on transmission of ON signals channelled by AII cells. However, its action on the OFF channel is largely unknown. We believe that some night vision disorders originate by imbalance in the dopaminergic system in the retina and its effects on AII cells. We will test our hypothesis by studying the modulatory effect of dopamine on calcium dependent signal transmission between AII cells and their partners in the OFF channel. Our hypothesis will be further tested by using animal models in which dopamine receptor function is altered. The results of these studies will provide us with an invaluable model to understand the physiological basis of the dark-light switch and of the role of dopamine in night vision disorders.Read moreRead less
Epileptic convulsions are common, disrupt social life and may occasionally cause death. They can occur spontaneously in individuals whose brains appear to be physically normal. Apart from the fact that epilepsy may run in families, the processes leading to spontaneous convulsions are not known. We measure the brain's electrical rhythms (EEG) to find out which rhythms are disturbed in people with epilepsy and whether these rhythms disrupt the brain to cause attacks. In preliminary studies in pati ....Epileptic convulsions are common, disrupt social life and may occasionally cause death. They can occur spontaneously in individuals whose brains appear to be physically normal. Apart from the fact that epilepsy may run in families, the processes leading to spontaneous convulsions are not known. We measure the brain's electrical rhythms (EEG) to find out which rhythms are disturbed in people with epilepsy and whether these rhythms disrupt the brain to cause attacks. In preliminary studies in patients with generalised epilepsy, we have identified abnormally strong rhythms that are almost certainly related to epilepsy causation and our studies are in part aimed at making our findings into a diagnostic test. Our findings may even enable individuals with epilepsy to test themselves for their immediate risk of seizure. Both of these outcomes should enable improved treatment for epilepsy. In addition to benefits in epilepsy, there are potential benefits in the diagnosis of cerebral degenerative disorders if changes in the rhythms also occur in these conditions.Read moreRead less