Table 1.
Responsiveness of astrocytes to adrenergic and L-lactate receptor activation.
| FRET nanosensor | Stimulus | n (%) | n (%) | n (%) | n (%) | n | |
|---|---|---|---|---|---|---|---|
| increase | decrease | transient decrease | unresponsive | all | |||
| Rat astrocytes | |||||||
| cAMP | ISO (10 μM) | 8 (100%) | 0 (0%) | 0 (0%) | 0 (0%) | 8 | |
| NA (1 μM) | 16 (100%) | 0 (0%) | 0 (0%) | 0 (0%) | 16 | ||
| L-lactate (20 mM) | 7 (36.8%) | 3 (15.8%) | 0 (0%) | 9 (47.4%) | 19 | ||
| 3Cl-5OH-BA (0.5 mM) | 9 (42.9%) | 2 (9.5%) | 0 (0%) | 10 (47.6%) | 21 | ||
| PKA | L-lactate (2 mM) | 0 (0%) | 0 (0%) | 0 (0%) | 7 (100%) | 7 | |
| L-lactate (20 mM) | 8 (57.1%) | 1 (7.1%) | 0 (0%) | 5 (35.7%) | 14 | ||
| 3Cl-5OH-BA (0.5 mM) | 9 (56.3%) | 2 (12.5%) | 0 (0%) | 5 (31.3%) | 16 | ||
| Glucose | ISO (200 μM) | 5 (16.1%) | 0 (%) | 0 (0%) | 26 (83.9%) | 31 | |
| NA (200 μM) | 8 (40%) | 0 (%) | 0 (0%) | 12 (60%) | 20 | ||
| L-lactate (2 mM) | 0 (0%) | 0 (0%) | 0 (0%) | 11 (100%) | 11 | ||
| L-lactate (20 mM) | 3 (15%) | 4 (20.0%) | 13 (65.0%) | 0 (0%) | 20 | ||
| 3Cl-5OH-BA (0.5 mM) | 1 (5.3%) | 13 (68.4%) | 1 (5.3%) | 4 (21.1%) | 19 | ||
| Lactate | ISO (200 μM) | 10 (63%) | 0 (0%) | 0 (0%) | 6 (27%) | 16 | |
| NA (200 μM) | 8 (88.9%) | 0 (0%) | 0 (0%) | 1 (11.1%) | 9 | ||
| L-lactate (20 mM) | 14 (93.3%) | 0 (0%) | 0 (0%) | 1 (6.7%) | 15 | ||
| 3Cl-5OH-BA (0.5 mM) | 14 (100%) | 0 (0%) | 0 (0%) | 0 (0%) | 14 | ||
| Mouse astrocytes | |||||||
| cAMP | WT | 3Cl-5OH-BA (0.5 mM) | 11 (68.8) | 0 (0) | 0 (0) | 5 (31.2) | 16 |
| Compound 2 (50 nM) | 10 (66.7%) | 0 (0) | 0 (0) | 5 (33.3%) | 15 | ||
| KO GPR81 | 3Cl-5OH-BA (0.5 mM) | 11 (73.3) | 0 (0) | 0 (0) | 4 (26.7) | 15 | |
| Compound 2 (50 nM) | 11 (100%) | 0 (0) | 0 (0) | 0 (0) | 11 | ||
ISO, isoprenaline; NA, noradrenaline; 3Cl-5OH-BA, 3-chloro-5-hydroxybenzoic acid; Compound 2, 4-methyl-N-(5-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)-4-(2-thienyl)-1,3-thiazol-2-yl)cyclohexanecarboxamide; n, number of cells studied. The increase or decrease in the FRET ratio signal was set by determining a threshold of 3 standard deviations of the average signal measured prior to the application of agents (baseline), as described (Horvat et al., 2016). The frequency of unresponsive cells did not differ in KO group compared to WT group, when treated with 3Cl-5OH-BA (P = 0.78). The frequency of unresponsive cells was significantly lower in KO group compared to WT group, when treated with Compound 2 (P = 0.03; chi-square statistic).