Calcium channels play a key role in the signal transduction between neurons in our brain. Many types of calcium channels with different biophysical and pharmacological properties have been identified. Among them, only N- and P/Q-type calcium channels have been generally thought to control transmitter release evoked by the nerve impulse. This view was challenged by the neuroscientists Ling-Gang Wu, J. Gerard G. Borst and Bert Sakmann at the Max Planck Institute for Medical Research in Heidelberg, Germany. They discovered as reported in the April 14 issue of PNAS (Vol. 95, Issue 8) that R-type calcium channels control transmitter release in presynaptic terminals of neurons that participate in localization of sound. This finding may apply to many other synapses in the brain.
Biophysical and pharmacological analysis has led to the description of six classes of calcium channels, usually referred to as L-, N-, P-, Q-, R- and T-type. Among them, only N- and P/Q-type calcium channels have been found to control transmitter release evoked by nerve impulses in all synapses examined so far. R-type calcium channels are high voltage-activated channels resistant to the known specific calcium channel blockers. Because of the lack of the specific blocker, and the difficulty in directly accessing the small presynaptic terminals (a special compartment for a neuron to communicate with the other via neurotransmitters), it could not be addressed whether R-type channels are present in the presynaptic terminals.
About three years ago, Borst and Sakmann (Journal of Physiology (London) 489, 825-840,
1995) found that the electrical signals in both the pre- and the postsynaptic sides of a single
synapse between neurons i
Contact: Ling-Gang Wu