Abstract
Cav1.3 is one of the voltage-gated L-type calcium channels, which plays an important role in controlling the activity in many types of excitable tissues. It controls, for example, the pacemaker function of the sinoatrial node, the auditory signal transduction at the level of the hair cells as well as the gain of the input-output function of motoneurons. This chapter presents the recent advances in the study of the distribution of Cav1.3 channels across the central nervous system, with a special focus on the spinal cord across several animal species including the cat, rat, mouse and turtle. The functions of the channel are discussed in relation to motor control, not least to the motoneurons themselves. In the spinal cord Cav1.3 has been found to be expressed in all of the above mentioned animal species; however its detailed distribution patterns have been shown to vary across species. In cats, rats and mice Cav1.3 was expressed in all parts of the spinal gray matter although in cats the expression in the dorsal horn was significantly less than in the ventral horn in comparison with the other two species. Furthermore, Cav1.3 immunoreactivity was significantly higher in ventral horn motoneurons than in neurons located in dorsal horn and intermediate zone. The spatial distribution of the channel immunoreactivity along the soma-dendritic axes seems also different in the different species. In cats and rats the neuronal somata were densely immunolabeled, although a clear immunoreactivity could also be seen in their primary and secondary dendritic branches. In mice Cav1.3 immunoreactivity was revealed to be mainly distributed in the dentrites, especially the distal dendrites. In turtles Cav1.3 immunoreactivity was found to be predominantly located on the motoneuronal dendrites, including their proximal and the distal parts, although it could also be seen on the cell somata. However, using antibodies from different sources different immunolabeling patterns have been produced, which raises the possibility that different antibodies may be specific for different splice variants that may have a specific soma-dendritic distribution. The distribution of Cav1.3 channels in the brain was mainly examined in rats and it was shown that the channel was expressed in the olfactory bulb, cerebral cortex, hippocampus, basal ganglia, diencephalon, cerebellum and brain stem. In the brain stem Cav1.3 was expressed extensively in different regions including both motor and sensory nuclei with the neurons in the former group being more densely immunolabeled than the later group. Some nuclei, which contain monoaminergic neurons, for example the locus coeruleus in rats, were also densely immunolabeled. Due to its low activation threshold, it is strongly believed that Cav1.3 is one of the main channel types that mediate the persistent inward currents (PICs) in spinal motoneurons. Although it is still under debate as to where the PICs originate along the soma-dendritic membrane, physiological evidence suggests that these currents mainly originate from dendrites, although it can also originate from neuronal somata. In motoneurons the PICs could evoke all-or-none plateau potentials following injection of brief current pulses. With normal synaptic excitation there is evidence for a gradual recruitment of the PICs. Since the Cav1.3 channels in motoneurons are facilitated by monoaminergic innervation it has been suggested that the PICs mediated by Cav1.3 may serve as a controlled amplifier of synaptic excitation to motoneurons.
| Original language | English |
|---|---|
| Title of host publication | Calcium Channels: Properties, Functions and Regulation : -- |
| Editors | Mark Figgins |
| Number of pages | 40 |
| Volume | -- |
| Place of Publication | Nova Science Publishers |
| Publication date | Mar 2012 |
| Edition | 1st |
| Pages | 1-41 |
| Chapter | 1 |
| ISBN (Print) | 978-1-61470-232-0 |
| Publication status | Published - Mar 2012 |