Ryan Williamson, Brigham Young University
Physiology and Developmental Biology
The hippocampus is thought to mediate learning and memory by altering the strength of synapses within its circuitry. In many cases, this synaptic plasticity can be induced by intracellular signaling molecules. Lipid-based intracellular signaling molecules called endocannabinoids have been shown to modulate or mediate synaptic plasticity among hippocampal pyramidal cells and stratum radiatum interneurons; however, the role of endocannabinoids in mediating synaptic plasticity among interneurons in the stratum oriens is still unclear. Our goal was to determine whether stratum oriens interneurons have the machinery necessary for endocannabinoid production and, if so, whether this machinery is expressed in a sub-type specific manner. To do this, we used patch clamp electrodes to extract single cells from rat hippocampal slices and analyzed the expression of endocannabinoid biosynthetic enzyme mRNA using quantitative real-time PCR. In this analysis, we examined cellular expression of two interneuron markers, GAD65 and GAD67, as well as several calcium-binding proteins and neuropeptides to determine interneuron subtype. We also analyzed cellular expression of several endocannabinoid biosynthetic enzymes, including N-acyl phosphatidylethanolamine phospholipase D, diacylglycerol lipase alpha, and 12-lipoxygenase, as well as type I metabotropic glutamate receptors. Preliminary data suggests that stratum oriens interneurons express mRNA necessary for endocannabinoid biosynthetic enzymes. Additionally, we identified interneurons that coexpress mRNA for somatostatin and diacylglycerol lipase, suggesting that O-LM cells or another somatostatin-positive interneuron subtype may possess the enzymes necessary to produce the endocannabinoid 2-arachidonoylglycerol. Further work will allow us to examine how endocannabinoid biosynthetic enzyme expression correlates with other interneuron subtypes in the stratum oriens.