  Glutamate and glycine are important neurotransmitters in the brain. An action
potential prop- agating in the terminal of a presynatic neuron causes the
release of glutamate and glycine in the synapse by vesicles fusing with the
cell membrane, which then activate various receptors on the cell membrane of
the post synaptic neuron. Entry of Ca2+ through the activated NMDA receptors
leads to a host of cellular processes of which long term potentiation is of
crucial importance because it is widely considered to be one of the major
mechanisms behind learning and memory. By analysing the readout of glutamate
concentration by the post synaptic neurons during Ca2+ signaling, we find that
the average receptor density in hippocampal neurons has evolved to allow for
accurate measurement of the glutamate concentration in the synaptic cleft.
