Neurotransmitter Time Constants (PSCs)

This page describes the time dependency of postsynaptic currents (PSCs), focusing on rise times and time constants of decay.

Summary

Your browser does not support SVG Your browser does not support SVG Biexponential values ( $\tau_\text{fast}$ and $\tau_\text{slow}$ ) are plotted as a weighted geometric mean.

Data

* 10-90% $t_\text{rise}$

Details

A single value for the decay time constant $\tau$ implies an exponential model: $I = I_0 \cdot e^{-t / \tau}$

Two values imply a biexponential model based on a fast component ( $\tau_f$ ) and slow component ( $\tau_s$ ): $I = I_{0,f} \cdot e^{-t / \tau_f} + I_{0,s} \cdot e^{-t / \tau_s}$ . This model also requires coefficients for each term. These may be given as absolute currents or charges, or relative percentages.

Primary Sources

Secondary Sources

Fourcard, N. & Brunel, N. (2002). Dynamics of the Firing Probability of Noisy Integrate-and-Fire Neurons. Neural Computation, 14(9). 2057-2110. Synaptic inputs to a cortical neuron come from different types of receptors with different temporal characteristics. Common types of receptors are AMPA, NMDA, and GABA receptors. AMPA receptors have synaptic time constants of the order of 2 ms (Hestrin, Sah, & Nicoll, 1990; Sah, Hestrin, & Nicoll, 1990; Spruston, Jonas, & Sakmann, 1995; Angulo, Rossier, & Audinat, 1999). GABA A receptors have longer time constants (typically 5-10 ms; Salin & Prince, 1996; Xiang, Huguenard, & Prince, 1998; Gupta, Wang, & Markram, 2000). Finally, NMDA currents are the slowest, with decay time constants of about 100 ms (Hestrin et al., 1990; Sah et al., 1990).

Moreno-Bote, R. & Parga, N. (2005). Simple model neurons with AMPA and NMDA filters: role of synaptic time scales. Neurocomputing, 65-66. 441-448. Fast AMPA receptors filter presynaptic inputs with a time constant of $\tau$ AMPA ~1-10ms, while NMDA filter them with a longer time scale $\tau$ NMDA ~50-150ms (Bear, Connors, & Paridiso, 1996).

Parisien, C., Anderson, C.H., Eliasmith, C. (2008). Solving the problem of negative synaptic weights in cortical models. Neural Computation. 20, 1473-1494. To determine the relevant biophysical parameters, we simulate hippocampal principal neurons with AMPA-mediated PSCs with decay constants of $\tau$ = 5 ms (Jonas et al., 1993). ... Hippocampal AMPA-mediated synapses on inhibitory interneurons are fast (Geiger et al., 1997; Carter and Regehr, 2002; Walker et al., 2002), being well modeled by PSCs with $\tau$ = 1 ms for these synapses. Slower GABA-mediated inhibitory synapses with $\tau$ = 4 ms project onto the B neurons (Bartos et al., 2001, 2002). We run this simulation using recurrent NMDA-mediated synapses with $\tau$ = 150 ms as is common (Kinney et al., 1994; Seung, 1996).

Potential sources

Glossary and abbreviations

ACh: acetylcholine

AMPA: $\alpha$ -amino-3-hydroxyl-5-methyl-4-isoxazole-propionate

-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate AP5 (also APV): (2R)-amino-5-phosphonovaleric acid

BC: basket cell

CA1-4: cornu ammonis subfields 1 to 4

CNQX: 6-cyano-7-nitroquinoxaline-2,3-dione

DA: dopamine

DHPG: (S)-3,5-dihydroxyphenylglycine

GABA: $\gamma$ -aminobutyric acid

-aminobutyric acid Glu: glutamate mGluR1: metabotropic glutamate receptor subtype 1

IG: infragranular

IN: (fast-spiking) interneuron

MF: mossy fibre

MSO: medial superior olive

NMDA: N-methyl-D-aspartic acid

nRt: nucleus reticularis

PFC: prefrontal cortex

PSC: postsynaptic current EPSC: excitatory PSC eEPSC: evoked EPSC IPSC: inhibitory PSC sIPSC: spontaneous IPSC eIPSC: evoked IPSC mIPSC: miniature IPSC

PN: principal neuron

SG: supragranular

$\tau$ : time constant

: time constant $t_\text{rise}$ : rise time (usually given as 20-80% or 10-90%)

: rise time (usually given as 20-80% or 10-90%) VB: ventrobasal

Contributing

If you would like to contribute to this list, please go to ctn-waterloo/psc-constants and make an issue or pull request.