Alex Straiker - US grants

[unreadable] DESCRIPTION (provided by applicant): By 1993, both known cannabinoid receptors had been identified. Since then, a key question has hovered over the cannabinoid field: is that all there is or do additional cannabinoid receptors remain to be discovered? Indirect evidence supports as many as three additional 'cannabinoid' receptors in the hippocampus, but no receptors have been molecularly identified. If it were possible to clearly identify and isolate a neuron mediating a non-CB1 cannabinoid response, then it should be possible using existing technologies to identify and clone the receptor. The cloning of a novel cannabinoid receptor would be a major development in the cannabinoid field. In the process of studying endocannabinoid plasticity in cultured autaptic hippocampal neurons (DSE) I have identified five subpopulations of excitatory neurons, two of which exhibit distinct responses to cannabinoids, even in the absence of CB1 receptors. Because autaptic neurons are solitary it is possible to extract the entire cell mass nearly intact. Thus I am in a position to pharmacologically identify and isolate examples of two neuronal subpopulations each expressing a distinct non-CB1 cannabinoid receptor. The specific aims of the proposal are to: 1. Characterize the cannabinoid-like response in both neuronal subpopulations using electrophysiological methods. This constitutes the bulk of proposed experiments and is largely independent of (but would be greatly enhanced by) Specific Aim #2. 2. Identify the two novel cannabinoid receptors. This will be done by extracting and amplifying RNA from each subpopulation, and then cloning the receptor using gene array and candidate gene approaches. Discovery of two new cannabinoid receptors would have considerable health implications. Marijuana is a major drug of abuse, acting via cannabinoid receptors. Knowing the identity and function of all cannabinoid receptors is key to understanding how marijuana affects the body. [unreadable] [unreadable] [unreadable]

DESCRIPTION (provided by applicant): GPR119 is a G protein-coupled receptor whose stimulation increases insulin secretion. GPR119 agonists are currently in phase II clinical trials as novel therapeutics for treating type II diabetes. However, the role of GPR119 has not been examined in the eye. In preliminary studies we have found that GPR119 and candidate endogenous ligands oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) are all present in the anterior eye of the mouse. Notably, GPR119 is expressed prominently in the trabecular meshwork, responsible for outflow of aqueous humor. Preliminary functional experiments show that OEA reduces intraocular pressure (IOP) by 30% in the mouse. Elevated IOP is associated with most forms of glaucoma, a major cause of blindness worldwide. Our results suggest that a GPR119-based signaling system is present in the anterior eye and that GPR119 regulates intraocular pressure. The proposal will test this hypothesis as three specific aims. 1) Where are GPR119 receptors expressed in the murine eye? We will determine the expression pattern of GPR119 using immunocytochemistry in frozen sections of mouse eye, with GPR119 knockout controls. We will separately evaluate GPR119 mRNA expression using RT-PCR. 2) Are the putative endogenous GPR119 ligands present in the murine anterior eye? Using LC-MS we will determine the levels and diurnal variation of PEA and OEA in the anterior eye of the mouse. 3) Does GPR119 activation reduce intraocular pressure in a mouse model? Using the Tonolab measurement system we will extend preliminary experiments by testing OEA, PEA, and the potent synthetic agonist AR231453, with GPR119 knockout animals as controls. We will also test the interaction of GPR119-mediated reduction of IOP with beta-adrenergic-, alpha-adrenergic- and prostaglandin-based IOP- lowering treatments. Preliminary results suggest that GPR119 may be an entirely new means of reducing IOP, with considerable implications for glaucoma and therefore of great therapeutic potential. PUBLIC HEALTH RELEVANCE: Our preliminary results provide strong evidence for a GPR119-based signaling system in the mammalian eye, with receptors, ligands and function in the form of a 30% reduction in intraocular pressure. Elevated intraocular pressure is implicated in glaucoma, which causes impaired vision in millions of people around the world. The identification of a novel pathway to lower intraocular pressure is therefore of great therapeutic interest.

The aim of this research is to investigate the role of brain-produced cannabinoids in how the world is perceived at the level of the first stage of sensory processing in the brain. Sensory system processing is critical for an animal's ability to function within an environment. Humans and higher predator species are primarily visually oriented but most lower animal species utilize olfaction, the sense of smell, as a primary sensory modality. The ability of the olfactory system to detect a huge array of chemicals across wide concentration ranges is a formidable brain processing task. Processing of odor information in the first brain relay station, the main olfactory bulb, is a major contributor to this striking dynamic range. The experiments will increase the understanding of olfactory processing with potential impact on other sensory systems with similar circuit building mechanisms. Understanding the action of cannabinoids on sensory processing will shed light on how cannabinoids lead to altered sensory perception. Rather than purely higher order hallucinogenic action, the experiments will reveal how primary sensory modulation is influenced by cannabinoids and may lead to a better understanding of drug seeking behaviors. This research will provide an educational and outreach experience of exceptional quality for students at all levels with an emphasis on minority students at Howard University. The aim is to broaden the participation of students with minority background to expand the population of minority students as the science workforce of the future.

Marijuana (cannabis) is the most commonly abused illicit drug in the USA. Its bioactive ingredient, THC, activates cannabinoid receptors in the brain in the same manner as brain-produced endogenous cannabinoids (endocannabinoids). The endocannabinoid system is an important intrinsic neuromodulatory system during normal brain function and impacts sensory processing. The experiments take advantage of the highly laminar organization of the main olfactory bulb and a growing body of knowledge on how this system processes sensory information. This research will investigate the role of endocannabinoids in the olfactory system using whole-cell patch-clamp recordings, signal imaging and various mouse strains. Specifically, the research will explore how endocannabinoids regulate the activity of output neuron sensitivity and dynamic range in the main olfactory bulb. This will be followed by studying if environmental conditions such as a change in olfactory input engage endogenously produced cannabinoids. The researchers will exploit olfactory deprivation to identify the cellular, membrane, pharmacologic and network properties of endocannabinoid-modulated neural processing in the main olfactory bulb.