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Table 3 Model Kinetics and Rate Constant Values.

From: A mathematical model of aging-related and cortisol induced hippocampal dysfunction

Abbreviation Description Default Values
kcrh Rate constant for generation of CRH 3.8 × 10-1
kacth Rate constant for generation of ACTH 1.085 × 10-1
kcor Rate constant for generation of cortisol 2.4 × 10-3
kcdeg Rate constant for the degradation of cortisol. 8.5 × 10-3
Vcrh Saturation level of inhibition for hypothalamic cells 1
Vacth Saturation level of inhibition for pituitary secretory cells 1
kda Dissociation constant for cortisol in the hypothalamus 50
kdc Dissociation constant for cortisol in the pituitary 50
kgr Concentration of cortisol at which GR receptors are 50% saturated. 1 × 108
kmr Concentration of cortisol at which MR is 50% of its max 2.5 × 103
kmad Rate constant for the deactivation of MR receptors 1
knon Rate constant for the inhibition of CA1 neurons by MR receptors. 4.99 × 10-2
kGRD Rate constant for degradation of GR activity 4.45 × 10-1
kngf Rate constant for stimulation of CA1 neurons by growth factors. 10 × 10-8
knps Rate constant for death of neurons. 4.5 × 10-2
kngfs Rate constant for neuronal growth factor decline. 1
knbd Rate constant for stimulation of NBD 5 × 10-2
kses Rate constant for stimulation of synaptic excitatory signals. 1.049
ksf Rate constant for stimulation of synaptic firing 1.049
kso Rate constant for stimulation of synaptic output. 1.049
kho Rate constant for stimulation of hippocampal output. 1.049
khos Rate constant for degradation of synaptic output 5.5 × 104
kSI Rate constant for inhibition of synaptic firing by synaptic inhibitory signals. 2.2 × 10-1
kSGR Rate constant for production of synaptic inhibitory signals. 4.45 × 10-1
ksos Rate constant for stimulation of synaptic firing. 1.049
ksisd Rate constant for decline in synaptic inhibitory signals 3.8 × 10-1
Vcrh Saturation level of inhibition for hypothalamic cells 1
Vacth Saturation level of inhibition for pituitary cells 1
VmaxMRA Maximum rate of activity of MR receptors 1 × 102
VmaxGRA Maximum rate of activity of GR receptors 1 × 102
Ngr Hill coefficient for GR receptor Activity 3.6
Nmr Hill coefficient for MR receptor activity 5.8
HV Volume of Hippocampus 100
  1. This table describes the rate constant expressions used to define the interaction between variables within the model. Rate constants were extrapolated and simplified from known biophysical and biochemical reactions within hippocampal and HPA tissues. Michalelis-Menton steady state enzyme substrate reactions and the Hill receptor-ligand binding equations were used to define interactions between model variables.