A Phenomenological Model of Synaptic Activity in the Blowfly Lamina
Estimates of the effective Poisson rate obtained from voltage recordings of Large Monopolar Cells (LMCs) in the blowfly lamina, measured in response to repeated light-contrast stimuli, are on the order of 5x105 events per second. These values imply that if vesicle exocytosis at photoreceptor-LMC synapse consisted of statistically independent quantal release events, the mean release rate would…
Blowfly lamina synapses exhibit a high rate of vesicle release events in response to visual stimuli. Estimates reveal that if these events were statistically independent quantal releases, a release rate of at least 400 vesicles per second per active zone would be required. However, this rate seems implausible, as it would involve a membrane turnover rate exceeding twice per second for the equivalent of all six photoreceptor axon terminals in a lamina cartridge.
To address this, the source material suggests that temporal regularization of release events, such as reducing low-frequency noise power spectral density, can increase the effective Poisson rate without changing the average release rate. Moreover, an opposing extracellular space chloride current may contribute to vesicle release regularization, although this connection was previously only qualitatively described.
The current study constructs a model that integrates these observations with other physiological parameters to explain vesicle release regularization in blowfly lamina synapses.
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