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Research Highlight
Purkinje Cell's Microenvironment May Be Regulated by Cerebellar Structure
A recent collaboration between NCMIR and the New York University Medical Center found that a cerebellar structure called the pinceau may regulate the microenviroment of the initial segment of the Purkinje cell axon.
The study, which will be featured on the cover of the Nov. 12, 2004 issue of Brain Research, examined the pinceau, which is formed by descending GABA-ergic basket cell axonal terminals converging on the initial axonal segment of the Purkinje cell. Results indicated the pinceau's unusual, highly specialized structural features may combine with the molecular composition to regulate the microenvironment of the initial segment of the Purkinje cell axon. The study also posits that the abundance of potassium channels and a brain-specific water channel, aquaporin-4 (AQP4), in the astrocytic processes of the pinceau suggests rapid ionic dynamics in the pinceau.
Authors Marketta Bobik, Mark H. Ellisman, and Maryann E. Martone of NCMIR, in collaboration with co-author Bernardo Rudy of the New York University Medical Center, used immunohistochemistry, electron microscopy, and electron tomography to examine the pinceau. AQP4 was studied using confocal and electron microscopy.
The cerebellar pinceau, a highly complex and anatomically unique structure within the mammalian nervous system, forms a dense terminal plexus around the initial segment of the Purkinje cell. The function and mode of action of the pinceau are not well understood because the majority of basket cell axons do not make identifiable synaptic contacts with the Purkinje cell axon. Anatomical studies, however, have shown pinceau fibers contain selective concentrations of several proteins as well as an abundance of voltage-gated potassium channel subunits. In this study, a member of the voltage-gated potassium channel family--the Shaw-related potassium channel subunit Kv3.2--was localized to the pinceau region.
The image shows a 3D tomographic reconstruction of basket cell terminals in the pinceau areas. Voltage-gated potassium channel subunits, Kv3.2, in the pinceau (red) are associated with vesicle-containing regions (yellow spheres) of the pinceau fibers. Basket cell processes are shown in different colors, whereas the initial segment (IS) is shown in brown. A small part of an astrocyte (blue) lies between the initial segment and the green basket cell terminal.
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