Davison A, Lux U, Brandstätter JH, Babai N (2022)
Publication Type: Journal article
Publication year: 2022
Book Volume: 42
Pages Range: 6325-6343
Journal Issue: 33
DOI: 10.1523/JNEUROSCI.1878-21.2022
It is a commonly accepted view that light stimulation of mammalian photoreceptors causes a graded change in membrane potential instead of developing a spike. The presynaptic Ca2+ channels serve as a crucial link for the coding of membrane potential variations into neurotransmitter release. Cav1.4 L-type Ca2+ channels are expressed in photoreceptor terminals, but the complete pool of Ca2+ channels in cone photoreceptors appears to be more diverse. Here, we discovered, employing whole-cell patch-clamp recording from cone photoreceptor terminals in both sexes of mice, that their Ca2+ currents are composed of low- (T-type Ca2+ channels) and high- (L-type Ca2+ channels) voltage-activated components. Furthermore, Ca2+ channels exerted self-generated spike behavior in dark membrane potentials, and spikes were generated in response to light/dark transition. The application of fast and slow Ca2+ chelators revealed that T-type Ca2+ channels are located close to the release machinery. Furthermore, capacitance measurements indicated that they are involved in evoked vesicle release. Additionally, RT-PCR experiments showed the presence of Cav3.2 T-type Ca2+ channels in cone photoreceptors but not in rod photoreceptors. Altogether, we found several crucial functions of T-type Ca2+ channels, which increase the functional repertoire of cone photoreceptors. Namely, they extend cone photoreceptor light-responsive membrane potential range, amplify dark responses, generate spikes, increase intracellular Ca2+ levels, and boost synaptic transmission.SIGNIFICANCE STATEMENT Photoreceptors provide the first synapse for coding light information. The key elements in synaptic transmission are the voltage-sensitive Ca2+ channels. Here, we provide evidence that mouse cone photoreceptors express low-voltage-activated Cav3.2 T-type Ca2+ channels in addition to high-voltage-activated L-type Ca2+ channels. The presence of T-type Ca2+ channels in cone photoreceptors appears to extend their light-responsive membrane potential range, amplify dark response, generate spikes, increase intracellular Ca2+ levels, and boost synaptic transmission. By these functions, Cav3.2 T-type Ca2+ channels increase the functional repertoire of cone photoreceptors.
APA:
Davison, A., Lux, U., Brandstätter, J.H., & Babai, N. (2022). T-Type Ca2+ Channels Boost Neurotransmission in Mammalian Cone Photoreceptors. The Journal of Neuroscience, 42(33), 6325-6343. https://dx.doi.org/10.1523/JNEUROSCI.1878-21.2022
MLA:
Davison, Adam, et al. "T-Type Ca2+ Channels Boost Neurotransmission in Mammalian Cone Photoreceptors." The Journal of Neuroscience 42.33 (2022): 6325-6343.
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