PT  - JOURNAL ARTICLE
AU  - Tamse, Catherine T.
AU  - Yamoah, Ebenezer N.
TI  - Elementary Properties of Axonal Calcium Currents in Type B Photoreceptors in <em>Hermissenda crassicornis</em>
AID  - 10.1523/JNEUROSCI.22-24-10533.2002
DP  - 2002 Dec 15
TA  - The Journal of Neuroscience
PG  - 10533--10538
VI  - 22
IP  - 24
4099  - http://www.jneurosci.org/content/22/24/10533.short
4100  - http://www.jneurosci.org/content/22/24/10533.full
SO  - J. Neurosci.2002 Dec 15; 22
AB  - Axons of the type B photoreceptors form synapses with hair cells and interneurons that are involved in classical conditioning inHermissenda. We examined the differences in the Ca2+ channels expressed in the soma and axons of the B photoreceptors by direct functional recordings of single-channel currents. Although the soma of the B cells express two Ca2+ current subtypes, a transient BayK 8644-insensitive (∼17 pS) current and a sustained BayK 8644-sensitive (∼10 pS) current, the axons expressed only the latter. The axonal Ca2+ current activated at potentials positive to −20 mV. Moreover, the Ca2+ channels are distributed heterogeneously along the length of the axon, with the higher channel density (∼10–15 channel μm−2) occurring at the distal one-third of the isolated axons, with respect to the soma. The regions of Ca2+ channel clusters may represent the presynaptic site of the photoreceptor–interneuron synapses. Furthermore, the high-density clusters of Ca2+channels may augment postsynaptic responses. The results of the present study represent the first direct recordings of Ca2+currents at presumed synaptic sites. Expression of different Ca2+ channel subtypes at distinct compartments of the type B photoreceptors may generate diverse Ca2+domains that may be required for neuronal plasticity inHermissenda.