Variable Loudness at Individual Excitatory Synapses

cells expressing a specific receptor, or do they integrate results of a combination of optical, electrophysiological, and pharmacological experiments to probe AMPA re-sensory stimuli from multiple subpopulations of taste neurons? Hoon et al. have shown that 20%–30% of ceptor occupancy at excitatory hippocampal synapses. They conclude that AMPA receptors are generally far taste receptor cells in taste buds of the fungiform and circumvallate papillae are, respectively, TR1 and TR2 from saturation, and, more importantly, that receptor occupancy can change profoundly from one release positive. If more than two or three additional receptors for either sweet or bitter chemicals were to be found, it event to the next because of variability in the peak concentration of glutamate in the synaptic cleft. would probably imply that individual taste receptor cells express more than one taste receptor gene. Thus, in Working with cultured hippocampal neurons, Liu et al. (1999) started by comparing miniature excitatory contrast to that of the vertebrate olfactory system, the molecular organization of the taste sensory system might postsynaptic currents (mEPSCs) recorded in cultured hippocampal neurons with the responses of individual not be able to afford discrimination between individual chemical stimuli. Is such discrimination achieved? If so, synapses to exogenous glutamate pulses applied via a closely positioned pipette. They identified relatively how? For the next few years, TR1 and TR2 are likely to provide precious tools to tackle the largely mysterious isolated synapses with the aid of the recycled vesicle marker FM1-43 and demonstrated that they were able logic of taste sensory signaling. This is but a taste of things to come. to avoid glutamate diffusion to neighboring synapses. The response to iontophoresed glutamate at a single synapse was much less variable than the mEPSCs. This Catherine Dulac result alone does not prove that receptor occupancy at Howard Hughes Medical Institute individual synapses is incomplete, because the mEPSCs Department of Molecular and Cellular Biology presumably arose from synapses scattered all over the Harvard University neuron. Each synapse might have been saturated, with Cambridge, Massachusetts 02138 relatively unvarying but distinctly different quantal amplitudes. However, the maximal response to ionto-and the synapse behaves almost as if fewer receptors 796–800. were present. A rapidly dissociating competitive antagonist , on the other hand, can be displaced by glutamate. The higher the glutamate concentration rises, the more likely it is to displace antagonist molecules from the receptors, making the antagonist disproportionately Variable Loudness at Individual …