Electrophysiological analysis of voltage-dependent currents in two types of periglomerular cells in the mouse olfactory bulb

Periglomerular cells represent an important class of interneurons of the olfactory bulb, contributing to the processing of olfactory information coming from the olfactory epithelium. Despite their involvement in the glomerular circuitry, a larger number of data is required to clarify their function. To further complicate matters, several types of periglomerular cells are described in literature. The main goal of my thesis is to provide new information about two types of periglomerular cells: dopaminergic and calretinin-positive neurons. They belong to different classes of periglomerular cells, suggesting distinct roles in modulating olfactory stimuli. Using patch clamp technique, in both whole cell and perforated patch configuration, properties of these periglomerular neurons have been illustrated. Electrophysiological experiments have been performed in two transgenic mouse strains, each one specific for a distinct periglomerular class. The first part of my thesis is focused on the investigation of the properties of h-current in the dopaminergic periglomerular neurons. Most of the experiments have been carried out in perforated patch, in order to minimize the disturbance of the intracellular fluid. Biophysical properties of h-current have been described, calculating the values of the main kinetic parameters. In addition, the influence of both thermic conditions and intracellular levels of cAMP on this conductance has been analyzed. The blockage of h-current suppresses the spontaneous firing of these neurons through its effect on the resting membrane potential. Finally, only noradrenaline have been observed to act on Ih, decreasing its amplitude. The second part of the thesis regards the calretinin-positive periglomerular cells. In whole cell configuration and under voltage clamp conditions, activation protocols have been applied to the cell membrane, in order to elicit a complete set of depolarization-evoked currents. The three main conductances (a fast transient sodium current, an A-type potassium current, and an L-type calcium current) have been further isolated and analyzed, determining their voltage dependence and kinetic properties. As a whole, all the data collected contribute to a better understanding of the functional role of the periglomerular cells in the glomerular network. The characterization of h-current in the dopaminergic cells enlarges the previous body of knowledge regarding this class of interneurons. On the other hand, the description of the properties of calretinin-positive cells represents their first electrophysiological analysis in literature.