Glaucoma is a leading cause of blindness worldwide, yet the reason for retinal ganglion cell damage within the optic nerve head (ONH) is not fully understood. Elevated intraocular pressure (IOP) is considered the primary cause of glaucoma, but recent studies suggest that decreased intracranial pressure (ICP) also contributes to glaucoma pathophysiology. IOP and ICP are dynamic, and evidence suggests that they are at least partially under central nervous system (CNS) control. Understanding the neurophysiologic mechanisms that control IOP and ICP variations is critical to understanding glaucoma pathogenesis and progression. Our lab has shown for the first time that chemical stimulation of the dorsomedial hypothalamus and surrounding perifornical area (DMH/PeF) in rodents evokes increases in IOP and ICP; however, there is a temporal shift in the time for each of these measures to peak. This results in a change in the trans-ONH pressure difference (i.e. IOP minus ICP) that is greater than the change in IOP or ICP alone. Further, defining this CNS pathway and the neurotransmitters involved in IOP and ICP regulation may provide targets for novel glaucoma therapies aimed at stabilizing the human translaminar pressure difference. The primary focus of this grant is to examine the CNS pathways controlling IOP and ICP, the primary drivers of the translaminar pressure difference in humans. Our central hypothesize is that central regulation of IOP and ICP is controlled, at least in part, neurons located in the DMH/PeF region. To test this we have proposed 3 specific aims: 1) We will pharmacologically characterize the increases in IOP and ICP after site-directed stereotaxic chemical stimulation of the DMH/PeF region using selective antagonists to various neurotransmitter receptors. 2) We will attempt to define the central nervous system afferent inputs to and efferent targets of the DMH/PeF neurons that might control IOP and ICP by using site-directed stereotaxic microinjections to stimulate various central nervous system nuclei and record the changes in IOP and ICP. 3) We will examine the role of certain specific neurotransmitters in regulating circadian changes in IOP and ICP by molecular- based and pharmacologic-based inhibition of the neurotransmitter system while using radio-telemetry to record IOP and ICP.
Glaucoma is one of the leading causes of blindness worldwide, yet we are still trying to develop a fundamental understanding of the mechanisms that cause this disease. While we know that increased eye pressure is a risk factor for glaucoma, recent evidence also indicates differences between eye pressure and brain pressure may also be a risk factor. The research described in this application is aimed at investigating how the brain controls both eye pressure and brain pressure with the goal of identifying novel treatment options for patients with glaucoma.