Antidepressant effects of selective adenosine receptor antagonists targeting the A1 and A2A receptors administered jointly with NMDA receptor ligands: behavioral, biochemical and molecular investigations in mice

Abstract

Background: The objective of the study was to ascertain the antidepressant potential of the co-administration of NMDA receptor ligands and selective adenosine A1 and A2A receptor antagonists.

Methods: The forced swim test (FST) and spontaneous locomotor activity test were carried out in adult male naïve mice. Before the behavioral testing, animals received DPCPX (a selective adenosine A1 receptor antagonist, 1 mg/kg) or istradefylline (a selective adenosine A2A receptor antagonist, 0.5 mg/kg) in combination with L-701,324 (a potent NMDA receptor antagonist, 1 mg/kg), D-cycloserine (a partial agonist at the glycine recognition site of NMDA receptor, 2.5 mg/kg), CGP 37849 (a competitive NMDA receptor antagonist, 0.3 mg/kg) or MK-801 (a non-competitive NMDA receptor antagonist, 0.05 mg/kg). Additionally, serum BDNF level and the mRNA level of the Adora1, Comt, and Slc6a15 genes in the murine prefrontal cortex were determined.

Results: The obtained results showed that DPCPX and istradefylline administered jointly with NMDA receptor ligands (except for DPCPX + D-cycloserine combination) produced an antidepressant effect in the FST in mice without enhancement in spontaneous motility of animals. An elevation in BDNF concentration was noted in the D-cycloserine-treated group. Adora1 expression increased with L-701,324, DPCPX + D-cycloserine, and DPCPX + CGP 37849, while D-cycloserine, CGP 37849, and MK-801 led to a decrease. Comt mRNA levels dropped with DPCPX + L-701,324, istradefylline + L-701,324/CGP 37849 but increased with D-cycloserine, MK-801, CGP 37849 and DPCPX + MK-801/ CGP 37849. Slc6a15 levels were reduced by D-cycloserine, DPCPX + L-701,324 but rose with DPCPX + CGP 37849/MK-801 and istradefylline + D-cycloserine/MK-801/CGP 37849.

Conclusion: Our study suggests that selective antagonists of adenosine receptors may enhance the antidepressant efficacy of NMDA receptor ligands highlighting a potential synergistic interaction between the adenosinergic and glutamatergic systems. Wherein, A2A receptor antagonists are seen as more promising candidates in this context. Given the intricate nature of changes in BDNF levels and the expression of Adora1, Comt, and Slc6a15 seen after drug combinations exerting antidepressant properties, further research and integrative approaches are crucial understand better the mechanisms underlying their antidepressant action.

Keywords: BDNF; DPCPX; Forced swim test; Gene expression; Istradefylline; NMDA receptor ligands.

Scheme 1

Research schedule. (A) Experiments with DPCPX; (B) Experiments with istradefylline. Abbreviations Adora1, adenosine A1 receptor gene; BDNF, brain–derived neurotrophic factor; Comt, catechol–O–methyl–transferase gene; FST, forced swim test; Slc6a15, solute carrier family 6 (neurotransmitter transporter) member 15 gene

Fig. 1

An influence of concomitant administration of (A) a selective A1 receptor antagonist– DPCPX, and (B) selective A2A receptor antagonist– istradefylline, with NMDA receptor ligands on mice behaviour in the forced swim test. Animals received intraperitoneally (ip) L–701,324 (1 mg/kg), D–cycloserine (2.5 mg/kg), CGP 37849 (0.3 mg/kg) or MK–801 (0.05 mg/kg) 60 min before the behavioural experiment. Istradefylline (0.5 mg/kg) was given orally (po) 60 min before the test, whereas DPCPX (1 mg/kg) was administered ip 30 min before the test. Mice from the control group received two administrations of saline, i.e. the first one po 60 min and the second ip 30 min prior behavioral testing. The following drug combinations were used: (1) saline + saline, (2) saline + DPCPX, (3) saline + istradefylline, (4) L–701,324 + saline, (5) L–701,324 + DPCPX, (6) L–701,324 + istradefylline, (7) D–cycloserine + saline, (8) D–cycloserine + DPCPX, (9) D–cycloserine + istradefylline, (10) CGP 37849 + saline, (11) CGP 37849 + DPCPX, (12) CGP 37849 + istradefylline, (13) MK–801 + saline, (14) MK–801 + DPCPX, (15) MK–801 + istradefylline. The values represent mean (s) ± SEM (n = 10 mice per group). Significance: ***p < 0.001, ****p < 0.0001 versus saline + saline-treated group; ^^^^p < 0.0001 versus saline + DPCPX- or saline + istradefylline-treated group (respectively), ^###p < 0.001, ^####p < 0.0001 versus saline + respective NMDA receptor ligand-treated group. Data were analysed by two-way ANOVA with Bonferroni’s post hoc test.

Fig. 2

An influence of concomitant administration of a selective A1 receptor antagonist– DPCPX, and selective A2A receptor antagonist– istradefylline, with NMDA receptor ligands on the BDNF levels in the murine serum. Animals received intraperitoneally (ip) L–701,324 (1 mg/kg), D–cycloserine (2.5 mg/kg), CGP 37849 (0.3 mg/kg) or MK–801 (0.05 mg/kg) 60 min before decapitation. Istradefylline (0.5 mg/kg) was given orally (po) 60 min before the procedure, whereas DPCPX (1 mg/kg) was administered ip 30 min before the procedure. Mice from the control group received two administrations of saline, i.e. the first one po 60 min and the second ip 30 min prior decapitation.The following drug combinations were used: (1) saline + saline, (2) saline + DPCPX, (3) saline + istradefylline, (4) L–701,324 + saline, (5) L–701,324 + DPCPX, (6) L–701,324 + istradefylline, (7) D–cycloserine + saline, (8) D–cycloserine + DPCPX, (9) D–cycloserine + istradefylline, (10) CGP 37849 + saline, (11) CGP 37849 + DPCPX, (12) CGP 37849 + istradefylline, (13) MK–801 + saline, (14) MK–801 + DPCPX, (15) MK–801 + istradefylline. The values represent mean (pg/ml) ± SEM (n = 6 mice per group). Significance: **p < 0.01, ***p < 0.001 versus saline + saline-treated group; ^p < 0.05 versus saline + DPCPX-treated group; ^##p < 0.01 versus saline + respective NMDA receptor ligand-treated group. Data were analysed by two-way ANOVA with Bonferroni’s post hoc test.

Fig. 3

An influence of concomitant administration of DPCPX and istradefylline with NMDA receptor ligands on the Adora1, Comt and Slc6a15 relative mRNA level in murine prefrontal cortex. Animals received intraperitoneally (ip) L–701,324 (1 mg/kg), D–cycloserine (2.5 mg/kg), CGP 37849 (0.3 mg/kg) or MK–801 (0.05 mg/kg) 60 min before decapitation. Istradefylline (0.5 mg/kg) was given orally (po) 60 min before the procedure, whereas DPCPX (1 mg/kg) was administered ip 30 min before the procedure. Mice from the control group received two administrations of saline, i.e. the first one po 60 min and the second ip 30 min prior decapitation.The following drug combinations were used: (1) saline + saline, (2) saline + DPCPX, (3) saline + istradefylline, (4) L–701,324 + saline, (5) L–701,324 + DPCPX, (6) L–701,324 + istradefylline, (7) D–cycloserine + saline, (8) D–cycloserine + DPCPX, (9) D–cycloserine + istradefylline, (10) CGP 37849 + saline, (11) CGP 37849 + DPCPX, (12) CGP 37849 + istradefylline, (13) MK–801 + saline, (14) MK–801 + DPCPX, (15) MK–801 + istradefylline. The values represent mean (relative mRNA level) ± SEM (n = 6 mice per group). Significance: *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 versus saline + saline-treated group; ^p < 0.05, ^^^p < 0.001, ^^^^p < 0.0001 versus saline + DPCPX- or saline + istradefylline-treated group (respectively); ^#p < 0.05, ^##p < 0.01, ^###p < 0.001, ^####p < 0.0001 versus saline + respective NMDA receptor ligand-treated group. Data were analysed by two-way ANOVA with Bonferroni’s post hoc test.