Neuronal voltage-gated Ca(2+) channels are involved in electrical signalling and in converting these signals into cytoplasmic calcium changes.One important function of voltage-gated Ca(2+) channels is generating regenerative dendritic Ca(2+) spikes.However, the Ca(2+) dependent mechanisms used to create these spikes are only partially understood.To start investigating this mechanism, we set out to kinetically and pharmacologically identify the sub-types of somatic voltage-gated Ca(2+) channels in pyramidal neurons from layer 5 of rat somatosensory cortex, using the here nucleated configuration of the patch-clamp technique.
The activation kinetics of the total Ba(2+) current revealed conductance activation only at medium and high voltages suggesting that T-type calcium channels were not present in the patches.Steady-state inactivation protocols in combination with pharmacology revealed the expression of R-type channels.Furthermore, pharmacological experiments identified 5 voltage-gated Ca(2+) channel sub-types - L-, N-, R- and P/Q-type.Finally, the activation of the Ca(2+) conductances was examined using physiologically derived voltage-clamp protocols including a calcium spike protocol and a mock back-propagating action potential (mBPAP) protocol.
These experiments enable us to suggest the possible contribution 2000 bmw 528i front bumper of the five Ca(2+) channel sub-types to Ca(2+) current flow during activation under physiological conditions.