Regulation of Firing Response Gain by Calcium-Dependent Mechanisms in Vestibular Nucleus Neurons

• Published in: Journal of neurophysiology 2002-04, Vol.87 (4), p.2031-2042
• Main Authors: Smith, Marianne R, Nelson, Alexandra B, du Lac, Sascha
• Format: Article
• Language: English
• Subjects: Amiloride - pharmacology; Animals; Calcium - physiology; Calcium Channels - physiology; Calcium Channels, N-Type - physiology; Calcium Channels, T-Type - physiology; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases - physiology; Electrophysiology; In Vitro Techniques; Large-Conductance Calcium-Activated Potassium Channels; Neurons - physiology; Nickel - pharmacology; Phosphoric Monoester Hydrolases - physiology; Potassium Channels - physiology; Potassium Channels, Calcium-Activated - physiology; Rats; Rats, Long-Evans; Small-Conductance Calcium-Activated Potassium Channels; Space life sciences; Vestibular Nuclei - cytology; Vestibular Nuclei - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00821.2001

Systems Neurobiology Laboratories, The Salk Institute for Biological Studies, La Jolla, California 92037 Smith, Marianne R., Alexandra B. Nelson, and Sascha du Lac. Regulation of Firing Response Gain by Calcium-Dependent Mechanisms in Vestibular Nucleus Neurons. J. Neurophysiol. 87: 2031-2042, 2002. Behavioral reflexes can be modified by experience via mechanisms that are largely unknown. Within the circuitry for the vestibuloocular reflex (VOR), neurons in the medial vestibular nucleus (MVN) show adaptive changes in firing rate responses that are correlated with VOR gain (the ratio of evoked eye velocity to input head velocity). Although changes in synaptic strength are typically assumed to underlie gain changes in the VOR, modulation of intrinsic ion channels that dictate firing could also play a role. Little is known, however, about how ion channel function or regulation contributes to firing responses in MVN neurons. This study examined contributions of calcium-dependent currents to firing responses in MVN neurons recorded with whole cell patch electrodes in rodent brain stem slices. Firing responses were remarkably linear over a wide range of firing rates and showed modest spike frequency adaptation. Firing response gain, the ratio of evoked firing rate to input current, was reduced by increasing extracellular calcium and increased either by lowering extracellular calcium or with antagonists to SK- and BK-type calcium-dependent potassium channels and N- and T-type calcium channels. Blockade of SK channels occluded gain increases via N-type calcium channels, while blocking BK channels occluded gain increases via presumed T-type calcium channels, indicating specific coupling of potassium channels and their calcium sources. Selective inhibition of Ca 2+ /calmodulin-dependent kinase II and broad-spectrum inhibition of phosphatases modulated gain via BK-dependent pathways, indicating that firing responses are tightly regulated. Modulation of firing response gain by phosphorylation provides an attractive mechanism for adaptive control of VOR gain. * M. R. Smith and A. B. Nelson contributed equally to this work.