Clozapine markedly elevates pregnenolone in rat hippocampus, cerebral cortex, and serum: candidate mechanism for superior efficacy?

Effects of olanzapine, sertindole and clozapine on MK-801 induced visual memory deficits in mice

We investigated the effects of the second generation antipsychotics olanzapine, sertindole and clozapine on visual recognition memory using the novel object recognition (NOR) test in naive and MK-801-treated animals. The effects of drug treatment on locomotion and anxiety were also determined using the open field test. Male Balb-c mice were treated with olanzapine (0.2, 0.4 and 0.6 mg/kg; i.p.), sertindole (0.63, 1.3 and 2.5mg/kg; s.c.) or clozapine (0.5 and 1mg/kg; i.p.), and cognitive deficits were induced by MK-801 (0.2mg/kg; i.p.) administration. Olanzapine treatment decreased the ratio index in the NOR test, whereas sertindole and clozapine had no effect in naive mice. MK-801-induced cognitive impairment was reversed by treatment with olanzapine, sertindole or clozapine. While olanzapine, sertindole and clozapine had no effect on the anxiety of naive mice as determined by the open field test, MK-801 significantly increased the total distance traveled, time spent in the center zone and the velocity of the animals. MK-801-induced effects on locomotion and anxiety in the open field test were reversed by olanzapine, sertindole or clozapine treatment. The results of the present study demonstrated that olanzapine, sertindole and clozapine improved cognition in MK-801 treated mice, and indicate that these drugs have a potential to improve cognition in schizophrenia.

Sex differences and hormonal influences in human sensorimotor gating: implications for schizophrenia

Prepulse inhibition (PPI) of the startle response serves to prevent the interruption of ongoing perceptual and early sensory analysis and provides a simple operational measure of sensorimotor gating. In line with postulated deficits in early stages of information processing, PPI is disrupted in schizophrenia. PPI is considered a valid candidate for an endophenotypic marker in genetic studies of schizophrenia and has also been extensively used in translational research. Importantly, there are well-replicated sex differences and menstrual phase effects in prepulse-elicited startle modulation of nonclinical young populations. Lack of knowledge about the precise roles of sex differences and hormonal effects in prepulse-elicited startle modulation and in the schizophrenia disease process presents a stumbling block to continuous progress in this field. This chapter reviews a wealth of data demonstrating sex and hormonal influences in prepulse-elicited startle modulation and considers their implications for our understanding of the pathophysiology, genetics, and potential treatments of schizophrenia.

Allopregnanolone levels are reduced in temporal cortex in patients with Alzheimer's disease compared to cognitively intact control subjects

The neurosteroid allopregnanolone has pronounced neuroprotective actions, increases myelination, and enhances neurogenesis. Evidence suggests that allopregnanolone dysregulation may play a role in the pathophysiology of Alzheimer's disease (AD) and other neurodegenerative disorders. Our prior data demonstrate that allopregnanolone is reduced in prefrontal cortex in male patients with AD compared to male cognitively intact control subjects, and inversely correlated with neuropathological disease stage (Braak and Braak). We therefore determined if allopregnanolone levels are also reduced in AD patients compared to control subjects in temporal cortex, utilizing a larger set of samples from both male and female patients. In addition, we investigated if neurosteroids are altered in subjects who are APOE4 allele carriers. Allopregnanolone, dehydroepiandrosterone (DHEA), and pregnenolone levels were determined in temporal cortex postmortem samples by gas chromatography/mass spectrometry, preceded by high performance liquid chromatography (40 subjects with AD/41 cognitively intact control subjects). Allopregnanolone levels are reduced in temporal cortex in patients with AD (median 2.68 ng/g, n=40) compared to control subjects (median 5.64 ng/g, n=41), Mann-Whitney p=0.0002, and inversely correlated with Braak and Braak neuropathological disease stage (Spearman r=-0.38, p=0.0004). DHEA and pregnenolone are increased in patients with AD compared to control subjects. Patients carrying an APOE4 allele demonstrate reduced allopregnanolone levels in temporal cortex (Mann-Whitney p=0.04). In summary, our findings indicate that neurosteroids are altered in temporal cortex in patients with AD and related to neuropathological disease stage. In addition, the APOE4 allele is associated with reduced allopregnanolone levels. Neurosteroids may be relevant to the neurobiology and therapeutics of AD.

Evidence for a role of progesterone in menstrual cycle-related variability in prepulse inhibition in healthy young women

Prepulse inhibition (PPI) of the startle response is sensitive to sex, with healthy young women showing less PPI compared with age-matched men, and varies according to the menstrual cycle phase in women. Relatively less is known regarding sex and hormonal influences in prepulse facilitation (PPF). Menstrual phase-related variability in PPI is suggested to be mediated by fluctuating estrogen level, based on the observations of more PPI in women during the follicular, relative to the luteal, phase. No study has directly assessed the relationship between fluctuating hormones and PPI or PPF levels over the human ovarian cycle. To examine the roles of circulating ovarian hormones in PPI and PPF, 16 non-smoking regularly menstruating healthy women were tested during both the follicular and luteal phases on PPI and PPF and provided saliva samples for measurement of 17beta-estradiol (estrogen), progesterone and testosterone. The results showed higher levels of 17beta-estradiol and progesterone during the luteal, relative to the follicular, phase; and more PPI during the follicular phase and more PPF during the luteal phase with comparable startle amplitude and habituation during the two phases. A larger increase in progesterone was associated with a smaller decrease in PPI from the follicular to the luteal phase. No significant associations were found between changes in PPI/PPF and estrogen levels. The findings confirm lower PPI during the luteal, compared with the follicular, phase and suggest a role for progesterone, more specifically an antipsychotic-like PPI-restoration action of progesterone, during the luteal phase in PPI of young women.

Anxiolytic-like property of risperidone and olanzapine as examined in multiple measures of fear in rats

Atypical antipsychotics are also used in the treatment of anxiety-related disorders. Clinical and preclinical evidence regarding their intrinsic anxiolytic efficacy has been mixed. In this study, we examined the potential anxiolytic-like effects of risperidone and olanzapine, and compared them with haloperidol, chlordiazepoxide (a prototype of sedative-anxiolytic drug) or citalopram (a selective serotonin reuptake inhibitor). We used a composite of two-way avoidance conditioning and acoustic startle reflex model and examined the effects of drug treatments during the acquisition phase (Experiment 1) or extinction phase (Experiments 2 and 3) on multiple measures of conditioned and unconditioned fear/anxiety-like responses. In Experiment 4, we further compared risperidone, olanzapine, haloperidol, citalopram and chlordiazepoxide in a standard elevated plus maze test. Results revealed three distinct anxiolytic-like profiles associated with risperidone, olanzapine and chlordiazepoxide. Risperidone, especially at 1.0mg/kg, significantly decreased the number of avoidance responses, 22kHz ultrasonic vocalization, avoidance conditioning-induced hyperthermia and startle reactivity, but did not affect defecations or time spent on the open arms. Olanzapine (2.0mg/kg, sc) significantly decreased the number of avoidance responses, 22kHz vocalization and amount of defecations, but it did not inhibit startle reactivity and time spent on the open arms. Chlordiazepoxide (10mg/kg, ip) significantly decreased the number of 22kHz vocalization, avoidance conditioning-induced hyperthermia and amount of defecations, and increased time spent on the open arms, but did not decrease avoidance responses or startle reactivity. Haloperidol and citalopram did not display any anxiolytic-like property in these tests. The results highlight the importance of using multiple measures of fear-related responses to delineate behavioral profiles of psychotherapeutic drugs.

Proof-of-concept trial with the neurosteroid pregnenolone targeting cognitive and negative symptoms in schizophrenia

The neurosteroid pregnenolone and its sulfated derivative enhance learning and memory in rodents. Pregnenolone sulfate also positively modulates NMDA receptors and could thus ameliorate hypothesized NMDA receptor hypofunction in schizophrenia. Furthermore, clozapine increases pregnenolone in rodent hippocampus, possibly contributing to its superior efficacy. We therefore investigated adjunctive pregnenolone for cognitive and negative symptoms in patients with schizophrenia or schizoaffective disorder receiving stable doses of second-generation antipsychotics in a pilot randomized, placebo-controlled, double-blind trial. Following a 2-week single-blind placebo lead-in, patients were randomized to pregnenolone (fixed escalating doses to 500 mg/day) or placebo, for 8 weeks. Primary end points were changes in BACS and MCCB composite and total SANS scores. Of 21 patients randomized, 18 completed at least 4 weeks of treatment (n=9/group). Pregnenolone was well tolerated. Patients receiving pregnenolone demonstrated significantly greater improvements in SANS scores (mean change=10.38) compared with patients receiving placebo (mean change=2.33), p=0.048. Mean composite changes in BACS and MCCB scores were not significantly different in patients randomized to pregnenolone compared with placebo. However, serum pregnenolone increases predicted BACS composite scores at 8 weeks in the pregnenolone group (r(s)=0.81, p=0.022). Increases in allopregnanolone, a GABAergic pregnenolone metabolite, also predicted BACS composite scores (r(s)=0.74, p=0.046). In addition, baseline pregnenolone (r(s)=-0.76, p=0.037), pregnenolone sulfate (r(s)=-0.83, p=0.015), and allopregnanolone levels (r(s)=-0.83, p=0.015) were inversely correlated with improvements in MCCB composite scores, further supporting a possible role for neurosteroids in cognition. Mean BACS and MCCB composite scores were correlated (r(s)=0.74, p<0.0001). Pregnenolone may be a promising therapeutic agent for negative symptoms and merits further investigation for cognitive symptoms in schizophrenia.

Simultaneous quantification of GABAergic 3alpha,5alpha/3alpha,5beta neuroactive steroids in human and rat serum

The 3alpha,5alpha- and 3alpha,5beta-reduced derivatives of progesterone, deoxycorticosterone, dehydroepiandrosterone and testosterone enhance GABAergic neurotransmission and produce inhibitory neurobehavioral and anti-inflammatory effects. Despite substantial information on the progesterone derivative (3alpha,5alpha)-3-hydroxypregnan-20-one (3alpha,5alpha-THP, allopregnanolone), the physiological significance of the other endogenous GABAergic neuroactive steroids has remained elusive. Here, we describe the validation of a method using gas chromatography-mass spectrometry to simultaneously identify serum levels of the eight 3alpha,5alpha- and 3alpha,5beta-reduced derivatives of progesterone, deoxycorticosterone, dehydroepiandrosterone and testosterone. The method shows specificity, sensitivity and enhanced throughput compared to other methods already available for neuroactive steroid quantification. Administration of pregnenolone to rats and progesterone to women produced selective effects on the 3alpha,5alpha- and 3alpha,5beta-reduced neuroactive steroids, indicating differential regulation of their biosynthetic pathways. Pregnenolone administration increased serum levels of 3alpha,5alpha-THP (+1488%, p<0.001), (3alpha,5alpha)-3,21-dihydroxypregnan-20-one (3alpha,5alpha-THDOC, +205%, p<0.01), (3alpha,5alpha)-3-hydroxyandrostan-17-one (3alpha,5alpha-A, +216%, p<0.001), (3alpha,5alpha,17beta)-androstane-3,17-diol (3alpha,5alpha-A-diol, +190%, p<0.01). (3alpha,5beta)-3-hydroxypregnan-20-one (3alpha,5beta-THP) and (3alpha,5beta)-3-hydroxyandrostan-17-one (3alpha,5beta-A) were not altered, while (3alpha,5beta)-3,21-dihydroxypregnan-20-one (3alpha,5beta-THDOC) and (3alpha,5beta,17beta)-androstane-3,17-diol (3alpha,5beta-A-diol) were increased from undetectable levels to 271+/-100 and 2.4+/-0.9 pg+/-SEM, respectively (5/8 rats). Progesterone administration increased serum levels of 3alpha,5alpha-THP (+1806%, p<0.0001), 3alpha,5beta-THP (+575%, p<0.001), 3alpha,5alpha-THDOC (+309%, p<0.001). 3alpha,5beta-THDOC levels were increased by 307%, although this increase was not significant because this steroid was detected only in 3/16 control subjects. Levels of 3alpha,5alpha-A, 3alpha,5beta-A and pregnenolone were not altered. This method can be used to investigate the physiological and pathological role of neuroactive steroids and to develop biomarkers and new therapeutics for neurological and psychiatric disorders.

Clozapine and olanzapine exhibit an intrinsic anxiolytic property in two conditioned fear paradigms: contrast with haloperidol and chlordiazepoxide

Psychotic fear and anxiety disturbances are seen at a relatively high frequency in patients with schizophrenia. Atypical anti-psychotics are believed to show superior efficacy in reducing these symptoms. However, clinical and preclinical evidence regarding their anxiolytic efficacy has been mixed. In this study, we evaluated the possible anxiolytic property of two atypicals clozapine and olanzapine and compared them with typical haloperidol and chlordiazepoxide (a prototype of sedative-anxiolytic drug) in two preclinical models of fear. In Experiment 1, we used a fear-induced passive avoidance and conditioned place aversion paradigm and examined the effects of clozapine (20 mg/kg, sc), haloperidol (0.05 mg/kg, sc) and chlordiazepoxide (10 mg/ kg, ip). In Experiments 2 and 3, we used a two-way active avoidance conditioning paradigm and further compared the effects of clozapine (20 mg/kg, sc), haloperidol (0.05 mg/kg, sc), chlordiazepoxide (10 mg/kg, ip) and three doses of olanzapine (0.5, 1.0, and 2.0 mg/kg, sc). Results show that clozapine and chlordiazepoxide, but not haloperidol, significantly attenuated the shock conditioning-induced place aversion, decreased the amount of defecations and the number of the 22-kHz vocalizations. Clozapine also reduced the shock conditioning-induced hyperthermia. Similar to clozapine, olanzapine also significantly decreased the amount of defecations and reduced the shock conditioning-induced hyperthermia, but it did not inhibit the 22-kHz vocalizations. This study demonstrates that clozapine and olanzapine possess an intrinsic anxiolytic property, which is not attributable to its superior anti-"psychotic" effect or its favorable effects on motor functions or learning and memory processes. These findings also suggest that the combined use of passive avoidance and active avoidance conditioning models can be useful in better differentiating typical and atypical anti-psychotics as well as anxiolytics.

Cerebrospinal fluid dehydroepiandrosterone levels are correlated with brain dehydroepiandrosterone levels, elevated in Alzheimer's disease, and related to neuropathological disease stage

OBJECTIVE

It is currently unknown whether cerebrospinal fluid (CSF) neurosteroid levels are related to brain neurosteroid levels in humans. CSF and brain dehydroepiandrosterone (DHEA) levels are elevated in patients with Alzheimer's disease (AD), but it is unclear whether CSF DHEA levels are correlated with brain DHEA levels within the same subject cohort. We therefore determined DHEA and pregnenolone levels in AD patients (n = 25) and cognitively intact control subjects (n = 16) in both CSF and temporal cortex.

DESIGN

DHEA and pregnenolone levels were determined by gas chromatography/mass spectrometry preceded by HPLC. Frozen CSF and temporal cortex specimens were provided by the Alzheimer's Disease Research Center at Duke University Medical Center. Data were analyzed by Mann-Whitney U test statistic and Spearman correlational analyses.

RESULTS

CSF DHEA levels are positively correlated with temporal cortex DHEA levels (r = 0.59, P < 0.0001) and neuropathological disease stage (Braak and Braak) (r = 0.42, P = 0.007). CSF pregnenolone levels are also positively correlated with temporal cortex pregnenolone levels (r = 0.57, P < 0.0001) and tend to be correlated with neuropathological disease stage (Braak) (r = 0.30, P = 0.06). CSF DHEA levels are elevated (P = 0.032), and pregnenolone levels tend to be elevated (P = 0.10) in patients with AD, compared with cognitively intact control subjects.

CONCLUSIONS

These findings indicate that CSF DHEA and pregnenolone levels are correlated with temporal cortex brain levels of these neurosteroids and that CSF DHEA is elevated in AD and related to neuropathological disease stage. Neurosteroids may thus be relevant to the pathophysiology of AD.

Neuroactive steroids, mood stabilizers, and neuroplasticity: alterations following lithium and changes in Bcl-2 knockout mice

Many neuroactive steroids (NS) demonstrate neurotrophic and neuroprotective actions, including protection against apoptosis via Bcl-2 protein. NS are altered in post-mortem brain tissue from subjects with bipolar disorder, and several agents with efficacy in mania elevate NS in rodents. We therefore hypothesized that lithium and valproate may elevate NS, and compensatory NS increases may occur in Bcl-2 knockout mice. NS levels (allopregnanolone, pregnenolone) were determined in frontal cortex by negative ion chemical ionization gas chromatography/mass spectrometry in male Wistar Kyoto rats treated chronically with lithium, valproate, or vehicle. NS were also investigated in heterozygous Bcl-2 knockout mice. Allopregnanolone levels are significantly elevated in lithium-treated (p<0.05), but not in valproate-treated, rats. Pregnenolone levels also tend to be higher following lithium treatment (p=0.09). Knockout of Bcl-2 significantly increases pregnenolone levels in mice (p<0.01), while allopregnanolone levels are unaltered. NS induction may be relevant to mechanisms contributing to lithium therapeutic efficacy and neuroprotection.

Olanzapine and fluoxetine administration and coadministration increase rat hippocampal pregnenolone, allopregnanolone and peripheral deoxycorticosterone: implications for therapeutic actions

Olanzapine and fluoxetine elevate the GABAergic neuroactive steroid allopregnanolone to physiologically relevant concentrations in rodent cerebral cortex. It is unknown if these agents also alter pregnenolone or deoxycorticosterone. Since olanzapine and fluoxetine in combination have clinical utility and may demonstrate synergistic effects, we investigated neuroactive steroid alterations following olanzapine, fluoxetine or coadministration. Male rats received IP vehicle, olanzapine, fluoxetine or the combination of both agents in higher-dose (0, 10, 20 or 10/20 mg/kg, respectively) and lower-dose (0, 5, 10 or 5/10 mg/kg, respectively) experiments. Pregnenolone and allopregnanolone levels in hippocampus were determined by gas chromatography/mass spectrometry. Peripheral deoxycorticosterone and other steroid levels were determined by radioimmunoassay. Olanzapine, fluoxetine or the combination increased hippocampal pregnenolone and serum deoxycorticosterone in both higher- and lower-dose experiments, and elevated hippocampal allopregnanolone in higher-dose conditions. No synergistic effects on pregnenolone or allopregnanolone were observed following olanzapine and fluoxetine coadministration compared to either compound alone. Pregnenolone and its sulfate enhance learning and memory in rodent models, and therefore pregnenolone elevations may be relevant to cognitive changes in psychotic and affective disorders. Since pregnenolone decreases have been linked to depression, it is possible that olanzapine- and fluoxetine-induced pregnenolone elevations may contribute to the antidepressant actions of these agents.