Katie Halstead 
Carroll College
Waukesha, WI
Faculty Mentor: Dr. Michelle Mynlieff 

In the past, the hippocampus was a popular region of the brain to study, not only because of its involvement with memory and seizure formation, but also because of its organization. The densely packed pyramidal cell layer was an easy target to aim at before the advent of more sophisticated instrumentation. This early work has led to a wide knowledge base regarding the circuitry of the hippocampus, which is important for the electrophysiological studies being performed today. The use of slice preparations for electrophysiological research has allowed researchers to identify the cell types from which they are recording. Unfortunately, the extensive neuronal connections that remain intact in the slice create a space clamp problem&emdash;the currents recorded in the soma may not reflect what is occurring at the far ends of the processes. To compensate for this dilemma, it is possible to record from cultured cells. When neuronal cells are cultured, their processes are cleaved off and the space clamp problem is eliminated. This procedure is performed under the assumption that when the processes are cleaved, the integral membrane components that were located in the processes are redistributed on the cell body and, therefore, the electrophysiological phenomenon recorded in the cell body can be considered to be a reflection of what occurs at the synapses. Since an interest of our lab is how calcium channels are modulated by neurotransmitters, the goal of this study was to confirm the assumption that calcium channels redistribute during culture. The importance of calcium in cellular communication has fueled many studies aimed at characterizing calcium channels and has led to the discovery of several channel types. These channels can be classified by their kinetics, using information such as voltage activation, conductance, and inactivation patterns, or by their pharmacology, based on toxins that selectively block particular channel types. Purification studies have also elucidated the molecular structure of these channels, which consist of _1-, _-, g-, and a2g- subunits. The a1-subunit is the primary transmembrane peptide and differs in individual calcium channel types. Therefore, an immunohistochemical localization of calcium channel types is possible through the use of antibodies made against the a1-subunits. The a1A, a1B, a1C, a1D, and a1E subunits correspond to P/Q, N, cardiac L, neuronal L, and R subtypes, respectively, as defined by electrophysiological and pharmacological studies. By staining cells after 1, 7, and 14 days in culture with antibodies specific for these subunits, we tested the hypothesis that there is a redistribution of calcium channel types in hippocampal CA1 interneurons when cultured. A qualitative analysis indicates that each of the calcium channel types are present on the soma of cells after one day in culture, with the darkest staining found for neuronal L-type and R-type channels. After 14 days in culture, a higher percentage of channels were found in the processes for all channel types.