The Neurosteroidogenic Enzyme 5α-Reductase Mediates Psychotic-Like Complications of Sleep Deprivation

Abstract

Acute sleep deprivation (SD) can trigger or exacerbate psychosis- and mania-related symptoms; the neurobiological basis of these complications, however, remains elusive. Given the extensive involvement of neuroactive steroids in psychopathology, we hypothesized that the behavioral complications of SD may be contributed by 5α-reductase (5αR), the rate-limiting enzyme in the conversion of progesterone into the neurosteroid allopregnanolone. We first tested whether rats exposed to SD may exhibit brain-regional alterations in 5αR isoenzymes and neuroactive steroid levels; then, we assessed whether the behavioral and neuroendocrine alterations induced by SD may be differentially modulated by the administration of the 5αR inhibitor finasteride, as well as progesterone and allopregnanolone. SD selectively enhanced 5αR expression and activity, as well as AP levels, in the prefrontal cortex; furthermore, finasteride (10-100 mg/kg, IP) dose-dependently ameliorated PPI deficits, hyperactivity, and risk-taking behaviors, in a fashion akin to the antipsychotic haloperidol and the mood stabilizer lithium carbonate. Finally, PPI deficits were exacerbated by allopregnanolone (10 mg/kg, IP) and attenuated by progesterone (30 mg/kg, IP) in SD-subjected, but not control rats. Collectively, these results provide the first-ever evidence that 5αR mediates a number of psychosis- and mania-like complications of SD through imbalances in cortical levels of neuroactive steroids.

Figure 1

Sleep deprivation (SD) induces behavioral phenotypes related to manic and psychotic alterations. In comparison with non-sleep deprived (NSD) controls, SD-subjected rats displayed no significant changes in (a) startle amplitude [F(1,19)=0.30, NS], but a marked reduction in (b) prepulse inhibition (PPI) [F(1,20)=24.39, P<0.0001]. Conversely, no differences were found in either (c) startle latency or (d) startle habituation (tested as interblock ratio; IBR). The analysis of locomotor activity (e–g) revealed that SD led to increased (e) horizontal [F(1,13)=11.01, P<0.01] and (f) vertical activity [F(1,13)=120.18, P<0.0001], but did not affect the duration of time spent in (g) the peripheral zone of the arena. In the wire-beam bridge experiment (h–j), SD-subjected rats exhibited a significant decrease in (i) latency to cross the bridge [F(1,13)=5.08, P<0.05] and (j) immobility duration [F(1,13)=7.02, P<0.05], but did not affect (k) the total distance traveled on the bridge. Notably, SD did not affect either total duration or frequency of exploratory activity directed towards either (k and l) novel objects or (m and n) social counterparts. Values represent mean±SEM for each group (n=7–11). *P<0.05; **P<0.01; ****P<0.0001, compared to NSD group.

Figure 2

Sleep deprivation (SD) increases protein expressions of both 5α-reductase isoforms (5αR1 and 5αR2) in different brain regions. SD-subjected rats exhibited increased 5αR1 expression in (a) the prefrontal cortex [F(1,10)=6.24, P<0.05] and (b) nucleus accumbens [F(1,8)=7.59, P<0.05], but not in (c) hippocampus or (d) amygdala. PPI average levels were negatively correlated with 5αR1 in the nucleus accumbens (f), but not in any other region (e, g, and h). SD led to a selective increase of 5αR2 expression in (i) the PFC [F(1,10)=14.39, P<0.01], but not in any other brain areas (j–l). Furthermore, the expression of 5αR2 in the PFC (m), but not in any other region (n–p) was negatively correlated with PPI levels. Bars represent means±SEM for each group (n=5–6). *P<0.05; **P<0.01, compared to non-sleep deprived (NSD) rats.

Figure 3

Effects of sleep deprivation (SD) on neurosteroid levels in the prefrontal cortex (PFC) and striatum (STR). (a) shows a schematic representation of the metabolic pathway converting pregnenolone (PREG) into progesterone (PROG), dihydroprogesterone (DHP) and allopregnanolone (AP). SD induced an enhancement in the PFC levels of AP (e) [F(1,18)=5.92; P<0.05], as well as its ratio with PROG (g) [F(1,18)=7.67; P<0.05]. Conversely, no significant differences were found in STR. 3β-HSD: 3β-hydroxysteroid dehydrogenase; 5αR: 5α-reductase; 3α-HSD: 3α-hydroxysteroid dehydrogenase. Values represent mean±SEM for each group (n=10). *P<0.05, compared to non-sleep deprived (NSD) rats.

Figure 4

Effects of finasteride (F), lithium (Li⁺) and haloperidol (Hal) on the behavioral changes induced by sleep deprivation (SD). (a) The startle response was significantly reduced by F(10–100 mg/kg) in both SD and non-sleep deprived (NSD) rats [Main effect for F: F(3,63)=12.04; P<0.0001; P<0.01 for the comparison between 10 mg/kg F and vehicle; Ps<0.001 for the comparisons between 25 and 100 mg/kg and vehicle]. Similarly, both Li+ and Hal reduced this index in SD and NSD rats [Main effect for Li+: F(1,39)=4.33; P<0.05; Main effect for Hal: F(1,39)=37.44; P<0.0001]. (b) The analysis of PPI determined that, while SD reduced PPI in rats treated with vehicle (VEH), this effect was reversed by both doses of F [SD x treatment interaction: F(3,67)=4.04; P<0.05; Ps<0.05 for comparisons between VEH-NSD vs VEH-SD; VEH-SD vs VEH-F25; and VEH-SD vs VEH-F100], as well as Li⁺ [SD x treatment interaction: F(1,38)=4.13; P<0.05; P<0.05 for comparison between VEH-SD and Li⁺-SD] and Hal [SD × treatment interaction: F(1,39)=4.34; P<0.05; P<0.05 for comparison between VEH-SD and Hal-SD]. (c) The analysis of horizontal locomotor activity revealed that VEH-treated, SD-subjected rats traveled for a longer distance than their NSD counterparts, and this enhancement was prevented by F25 [SD × treatment interaction: F(1,41)=6.80; P<0.05 for comparison between VEH-NSD vs VEH-SD; P<0.001 for comparison between VEH-SD and F25-SD] conversely, both Li⁺ and Hal reduced activity irrespective of the condition [Main effect for Li⁺: F(1,41)=24.94; P<0.0001; Main effect for Hal: F(1,37)=41.09; P<0.0001]. (d) Similarly, SD increased vertical activity, in a fashion sensitive to F [SD × treatment interaction: F(1,42)=8.79; P<0.01; P<0.01 for comparison between VEH-NSD vs VEH-SD; P<0.001 for comparison between VEH-SD and F25-SD] and Li⁺ [SD x treatment interaction: F(1,43)=6.00; P<0.05; P<0.01 for comparison between VEH-SD and Li⁺-SD] conversely, Hal reduced vertical movements in both SD and NSD rats [Main effect for Hal: F(1,38)=35.74; P<0.0001]. (e) SD also reduced the latency of rats to cross a suspended wire-beam bridge, and this effect was significantly reversed by F [SD × treatment interaction: F(1,44)=5.94; P<0.05; P<0.01 for comparison between VEH-NSD vs VEH-SD; P<0.001 for comparison between VEH-SD and F25-SD] and Li⁺ [SD × treatment interaction: F(1,42)=4.36; P<0.05; P<0.05 for comparison between VEH-SD and Li⁺-SD]. (f) The immobility on the bridge was dramatically increased by F25 only in NSD, but not in SD rats F [SD × treatment interaction: F(1,39)=33.38; P<0.0001; Ps<0.001 for comparisons between VEH-NSD vs F-NSD and F-NSD vs F-SD] conversely, Li⁺ did not significantly affect this parameter, irrespective of the conditions. Values represent mean±SEM for each group (n=8–12). *P<0.05; **P>0.01; ***P<0.001 for interaction effects (indicated by brackets). ^oP<0.05; ^ooP<0.01; ^ooooP<0.0001 for main treatment effects. The doses of F are indicated in mg/kg (IP).

Figure 5

Effects of allopregnanolone (AP, 10 mg/kg, IP) and progesterone (PROG, 30 mg/kg, IP), in combination with finasteride (FIN, 25 mg/kg, IP) on (a and c) startle response and (b and d) prepulse inhibition (PPI) in sleep-deprived (SD) and non-sleep-deprived (NSD) rats. A 2-way interaction between AP and FIN (but not SD conditions) was found in the analysis of startle values (a) [F(1,82)=5.45, P<0.05]. This effect was shown to reflect significant differences between the rats treated with both vehicles and those treated with either AP or FIN (Ps<0.01 for both comparisons). The analysis of PPI values (b) revealed a significant SD × FIN × AP interaction [F(1,82)=4.44; P<0.05]. Post-hoc analyses confirmed that SD reduced PPI in rats (P<0.05 for comparison between SD and NSD rats treated with vehicles), and showed that this effect was significantly exacerbated by AP (P<0.01), and reduced by FIN (P<0.05). However, the PPI of SD rats treated with FIN and AP was significantly higher than those treated with vehicle and AP (P<0.01) and lower than those treated with vehicle and FIN (P<0.05). The evaluation of the effects of PROG on startle amplitude (c) revealed a significant SD x FIN x PROG interaction [F(1,91)=4.74; P<0.05], which was found to depend on a FIN-induced significant reduction on startle amplitude in NSD rats (P<0.05). Furthermore, the analysis of PPI (d) showed a significant three-way interaction [F(1,91)=9.035, P<0.05]. Post-hoc comparisons confirmed a significant difference between NSD and SD rats, and revealed that both PROG and FIN countered the PPI deficits induced by SD (P<0.01 and P<0.001, respectively). Values represent mean±SEM for each treatment group (n=8–12). V, vehicle of AP/PROG; VEH, vehicle of FIN. *P<0.05; **P<0.01; ***P<0.001. Brackets indicate significant differences between experimental groups.