Table 2. Mean substrate flow rate changes as a function of cell stimulation and glycogen metabolism.
| Stimulationa | Na+ influxb | Glycogenolysis | Neuronal flow ratec | Astrocytic flow ratec | ||
|---|---|---|---|---|---|---|
| Glucose | Lactate | Glucose | Lactate | |||
| Rest | Active/inactive | −4.36 | 0.21 | −1.34 | 0.07 | |
| High astrocytic activation | 175:155 (1.5:1) | Active | −5.32 | 0.29 | −0.90 | 0.09 |
| Inactive | −5.06 | 0.23 | −1.54 | 0.18 | ||
| Low astrocytic activation | 190:65 (3:1) | Active | −5.52 | 0.67 | −0.98 | –0.30 |
| Inactive | −5.53 | 0.66 | −1.01 | –0.32 | ||
a
As neuronal versus astrocytic Na+ influx ratio. Flow rates for steady-state resting condition apply for both 1.5:1 and 3:1 stimulations.
b
As mmol/L of Na+ entry into cells induced by the stimulation. The actual activation ratio is enclosed in parenthesis.
c
As glucose equivalents. Positive (negative) values mean release (uptake) from (to) interstitium for neurons, and interstitium plus basal lamina for astrocytes.
Note that the overall glucose uptake by the brain (i.e., sum of neuronal and astrocytic glucose uptake) during high astrocytic activation is greater when glycogenolysis is inactive.
All values are expressed in units μmol/L per s.