Synaptic contacts are believed to provide the morphological basis for information processing in the brain. Joachim Kirsch and Heinrich Betz from the Max Planck Institute for Brain Research (Frankfurt/Germany) report in "nature" (April 16) that neurotransmitter-triggered activity of the postsynaptic cell is a key signal for synapse formation.
Nerve cells communicate via specialized cell-cell contacts, the so-called synapses. Upon stimulation of the presynaptic cell, neurotransmitter is released from its nerve endings. The released transmitter molecules diffuse to the adjacent nerve cell and activate specific receptor proteins that are highly concentrated within the membrane segment underlying the presynaptic nerve terminal, the postsynaptic membrane proper. By culturing embryonic spinal cord neurons and pharmacological approaches Joachim Kirsch and Heinrich Betz, both from the Max Planck Institute for Brain Research (Frankfurt/Germany), now (nature, 392, 717-720) show that neurotransmitter-induced activity of the postsynaptic nerve cell is required for inducing the aggregation of receptors for the amino acid glycine, the major inhibitory neurotransmitter in the spinal cord.
Already in 1993, these scientists had reported (also in "nature") that the accumulation of the
glycine receptor-associated cytoplasmic protein gephyrin at developing postsynaptic sites
preceeds clustering of the glycine receptor, and that the expression of this peripheral
membrane protein is essential for the formation of postsynaptic glycine receptor aggregates. It
remained enigmatic, however, which signals instruct a cytoplasmic protein about the presence
or absence of an apposing glycinergic nerve terminal. By paralyzing
Contact: Joachim Kirsch & Heinrich Betz