Delta-9 Tetrahydrocannabinol (THC), the principal behaviorally active constituent in marijuana can affect the activity or functioning of a variety of membrane-associated enzymes and receptors. THC can also have a fluidizing or disordering affect on artificial lipid bilayer membranes (liposomes) and synaptic plasma membranes. Based on observations of this type, a hypothesis has been proposed stating that the effects of THC and other cannabinoids are due in part to the effects of these compounds on the ordering of biological membranes or specific regions within the membrane. The experiments in this proposal should enable us to describe and quantify the effects of several cannabinoids on the fluidity of biological and artificial membranes and explore the relationship of these changes to effects of these same compounds on adrenergic receptors and their associate adenylate cyclase and on Na+ K+-ATPase. Plasma membranes will be prepared from rat brain, heart, and liver. The effects of two cannabinoids with marijuana-like behavioral activity and three with little or no marijuana-like behavioral activity on membrane ordering (fluidity) will be determined using fluorescence polarization techniques. Similar studies will be performed using artificial lipid bilayers with a variety of lipid compositions and initial fluidities. The effects of the same cannabinoids on Beta-adrenergic receptors and their coupled adenylate cyclase and on Na+-K+-ATPase will also be examined in brain, heart, and liver. Arrhenius plots for the enzyme activities will also be determined. As these studies are performed, the developing pattern of relationships between membrane type (initial fluidity), fluidity changes, and changes in enzymes and receptors will be analyzed for both the psychoactive (THC-like) and non-psychoactive cannabinoids. It is hoped that a consistent pattern of changes will emerge that will increase our insight into the molecular actions of marijuana and its constituents.
