Simulation of Dendritic CaV1.3 Channels in Cat Lumbar Motoneurons: Spatial Distribution

• Published in: Journal of neurophysiology Vol. 94; no. 6; pp. 3961 - 3974
• Main Authors: ElBasiouny, Sherif M, Bennett, David J, Mushahwar, Vivian K
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01.12.2005
• Subjects: Animals; Calcium Channels, L-Type - physiology; Cats; Computer Simulation; Dendrites - physiology; Electric Stimulation - methods; Evaluation Studies as Topic; Imaging, Three-Dimensional - methods; Lumbosacral Region; Membrane Potentials - physiology; Models, Neurological; Motor Neurons - cytology; Motor Neurons - physiology; Patch-Clamp Techniques; Spinal Cord - cytology; Synapses - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00391.2005

1 Department of Biomedical Engineering, and 2 Centre for Neuroscience, Faculty of Medicine and Dentistry; and 3 Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada Submitted 18 April 2005; accepted in final form 19 August 2005 We used computer simulations to study the dendritic spatial distribution of low voltage-activated L-type calcium (Ca V 1.3 type) channels, which mediate hysteretic persistent inward current (PIC) in spinal motoneurons. This study was prompted by the growing experimental evidence of the functional interactions between synaptic inputs and active conductances over the motoneuron dendritic tree. A compartmental cable model of an adult cat -motoneuron was developed in NEURON simulation environment constituting the detailed morphology of type-identified triceps surae -motoneuron and realistic distribution of group Ia afferent-to-motoneuron contacts. Simulations of different distributions of Ca V 1.3 channels were conducted and the resultant behavior was compared to experimental data. Our results suggest that Ca V 1.3 channels do not uniformly cover the whole motoneuron dendritic tree. Instead, their distribution is similar to that of synaptic contacts. We found that Ca V 1.3 channels are primarily localized to a wide intermediate band overlapping with the dendritic Ia-synaptic territory at dendritic distances of 300 to 850 µm (0.62 ± 0.21 ) from the soma in triceps surae -motoneurons. These findings explain the functional interaction between synaptic inputs and the Ca V 1.3 channels over the motoneuron dendritic tree. Address for reprint requests and other correspondence: V. K. Mushahwar, 513 Heritage Medical Research Center, Department of Biomedical Engineering, Centre for Neuroscience, University of Alberta, Edmonton, Alberta T6G 2S2, Canada (E-mail: Vivian.Mushahwar{at}ualberta.ca )