Novel treatments for anxiety and depression: hurdles in bringing them to the market

1,8-cineole (eucalyptol): A versatile phytochemical with therapeutic applications across multiple diseases

1,8-cineole (Eucalyptol), a naturally occurring compound derived from botanical sources such as eucalyptus, rosemary, and camphor laurel, has a long history of use in traditional medicine and exhibits an array of biological properties, including anti-inflammatory, antioxidant, antimicrobial, bronchodilatory, analgesic, and pro-apoptotic effects. Recent evidence has also indicated its potential role in managing conditions such as Alzheimer's disease, neuropathic pain, and cancer. This review spotlights the health advantages of 1,8-cineole, as demonstrated in clinical trials involving patients with respiratory disorders, including chronic obstructive pulmonary disease, asthma, bronchitis, and rhinosinusitis. In addition, we shed light on potential therapeutic applications of 1,8-cineole in various conditions, such as depression, epilepsy, peptic ulcer disease, diarrhea, cardiac-related heart diseases, and diabetes mellitus. A comprehensive understanding of 1,8-cineole's pharmacodynamics and safety aspects as well as developing effective formulations, might help to leverage its therapeutic value. This thorough review sets the stage for future research on diverse health benefits and potential uses of 1,8-cineole in tackling complex medical conditions.

Antidepressant- and anxiolytic-like actions of Cajanus cajan seed extract mediated through monoaminergic, nitric oxide-cyclic GMP and GABAergic pathways

ETHNOPHARMACOLOGICAL RELEVANCE

The seeds of Cajanus cajan (L) Millsp, are used in Traditional medicine for the treatment of anxiety and other neurological disorders. Hence, this study is designed to investigate the antidepressant- and anxiolytic-like properties of ethanol seed extract of Cajanus cajan (CC) in mice.

MATERIALS AND METHODS

CC (50, 100 or 200 mg/kg, p.o.) was administered 1h before subjecting the animals to different behavioral models: forced swim test (FST) and tail suspension test (TST) (depressive-like behaviour), open field test (OFT), elevated plus maze (EPM), light-dark test (LDT) and hole-board test (HBT) for anxiety-like behaviour. To ascertain the pharmacodynamic of CC mice were pretreated with monoaminergic, nitrergic and GABAergic receptors antagonists. As well as molecular docking analysis of about 19 flavonoids present in CC on GABA_A, α₂ adrenoceptors and 5-HT_2A receptors.

RESULTS

CC (50, 100 or 200 mg/kg, p.o.) treatment significantly reduced immobile time in both FST and TST when compared with vehicle-treated control. However, the pretreatment of mice with prazosin/yohimbine (α_1/2 adrenoceptor antagonists, respectively), WAY100635 (5-HT_1A receptor antagonist), ketanserin (5-HT_2A receptor antagonist), sulpiride (dopamine D₂ receptor antagonist), L-N^G-Nitro arginine methyl ester (L-NAME), or methylene blue reversed the antidepressant-like effect of CC. In anxiety model, CC produced significant (p < 0.05) increase in open arms exploration and head dipping behavior which was reversed by flumazenil (benzodiazepine receptor antagonist) in the EPM. Docking analysis showed significant binding affinity of orientin, vitexin, pinostrobin and quercetin with 5HT_2A, α₂-adrenoceptor and GABA_A receptors.

CONCLUSION

Findings from this study showed that C.cajan seeds extract exerts antidepressant-like effect through participation of monoaminergic systems (5-HT₂ receptor, α₁/α₂-adrenoceptors, and dopamine D₂-receptors), nitric oxide-cyclic GMP pathway and anxiolytic-like effect via GABA_A benzodiazepine receptors. Moreso, presence of flavonoids with significant binding energies with monoaminergic and GABAergic systems support the potential of the extract in the management of mixed anxiety-depressive illness.

Deciphering the Pharmacological Properties of Methanol Extract of Psychotria calocarpa Leaves by In Vivo, In Vitro and In Silico Approaches

The present study explores the neuropharmacological, antinociceptive, antidiarrheal, antioxidant, thrombolytic and cytotoxic activity of methanol extract of Psychotria calocarpa leaves (MEPC). In anxiolytic activity testing of MEPC by elevated plus maze test, hole-board test and light-dark test, the extract exhibited a dose-dependent reduction of anxiety while the open field test observed a decreased locomotion. The administration of MEPC revealed a significant dose-dependent reduction of depressant behavior in forced swimming and tail suspension test. Additionally, the antinociceptive and antidiarrheal activity exposed a significant reduction of nociception and diarrheal behavior at the highest dose. In addition, a strong antioxidant activity was observed in DPPH-free radical-scavenging assay (IC50 = 461.05 μg/mL), total phenol content (118.31 ± 1.12 mg) and total flavonoid content (100.85 ± 0.97 mg). The significant clot-lysis activity was also observed with moderate toxicity (LC50 = 247.92 μg/mL) level in the lethality assay of brine shrimp. Moreover, in silico molecular docking study showed that the compound Psychotriasine could offer promising active site interactions for binding proteins. Furthermore, ADME/T and toxicological properties of the compound satisfied the Lipinski's rule of five and Veber rules for drug-like potential and toxicity level. Overall, MEPC had a potential neuropharmacological, antinociceptive, antidiarrheal and antioxidant activity that warranted further investigation.

Inhalation Administration of the Bicyclic Ethers 1,8- and 1,4-cineole Prevent Anxiety and Depressive-Like Behaviours in Mice

The anxiolytic and antidepressant-like activities of the naturally occurring monoterpene 1,8-cineole and its structural isomer 1,4-cineole were evaluated in mice via inhalation administration at doses ranging from 4 × 10-6 to 4 × 10-1 mg per 400 μL of triethyl citrate. Mice were tested for anxiety-like behaviours by using the light-dark box test (LDB) and marble-burying test (MBT) and for depression-like symptoms by using the forced swimming test (FST) and tail suspension test (TST). Diazepam and fluoxetine were used as standard drugs for anxiolytic and antidepressant tests, respectively. The results showed that 1,8-cineole at 4 × 10-4 mg, and 1,4-cineole at 4 × 10-4 and 4 × 10-3 mg significantly increased the amount of time spent in the light box and the number of entries in the light box in the LDB as well as reduced the number of marbles buried in the MBT relative to those in the control, suggesting an anxiolytic effect. Similarly, 1,8-cineole at 4 × 10-4 and 4 × 10-2 mg and 1,4-cineole at doses of 4 × 10-4 to 4 × 10-2 mg significantly reduced immobility times in the FST and TST relative to those of the control, suggesting an antidepressant activity. The role of the GABAA/benzodiazepine receptor system in the anxiolytic effects of 1,8- and 1,4-cineole was investigated through co-administration of flumazenil, a GABAergic system antagonist. Flumazenil reversed the effects of diazepam and 1,8-cineole, suggesting that 1,8-cineole affects the GABAA/benzodiazepine receptors. Collectively, the results suggest that inhaled 1,8- and 1,4-cineole prevented anxiety and depressive-like symptoms in classic mice models.

Metformin produces anxiolytic-like effects in rats by facilitating GABAA receptor trafficking to membrane

BACKGROUND AND PURPOSE

Altered function or expression of GABA_A receptors contributes to anxiety disorders. Benzodiazepines are widely prescribed for the treatment of anxiety. However, the long-term use of benzodiazepines increases the risk of developing drug dependence and tolerance. Thus, it is urgent to explore new therapeutic approaches. Metformin is widely used to treat Type 2 diabetes and other metabolic syndromes. However, the role of metformin in psychiatric disorders, especially anxiety, remains largely unknown.

EXPERIMENTAL APPROACH

We examined the effects of metformin on anxiety-like behaviour of rats in open field test and elevated plus maze test. We also observed the effect of metformin (10 μM, in vitro; 100 mg·kg^-1 , in vivo) on the trafficking of GABA_A receptors, as mechanisms underlying the anxiolytic effects of metformin.

KEY RESULTS

Metformin (100 mg·kg^-1 , i.p. 30 min) displayed a robust and rapid anxiolytic effect, without tolerance. Metformin up-regulated the surface expression of GABA_A receptors and increased miniature inhibitory postsynaptic currents (mIPSCs). AMP-activated protein kinase (AMPK) activated by metformin-induced stimulation of forkhead box O3a (FoxO3a) transcriptional activity, followed by increased expression of GABA_A receptor-associated protein (GABARAP) and its binding to GABA_A receptors finally resulted in the membrane insertion of GABA_A receptors.

CONCLUSIONS AND IMPLICATIONS

Metformin increased mIPSCs by up-regulating the membrane insertion of GABA_A receptors, via a pathway involving AMPK, FoxO3a, and the GABA_A receptor-associated protein. Thus metformin has a potential new use in the treatment of anxiety disorders.

Antidepressant & anxiolytic activities of N-(pyridin-3-yl) quinoxalin-2-carboxamide: A novel serotonin type 3 receptor antagonist in behavioural animal models

Background & objectives:

Alteration in the serotonin leads to the psychological illness, such as depression, anxiety, schizophrenia, eating disorders, obsessive-compulsive disorder, panic disorders and migraines. The objective of the current study was to investigate the antidepressant and anxiolytic activities of N-(pyridin-3-yl) quinoxalin-2-carboxamide (QCF-21), a novel 5-HT₃ receptor antagonist in preclinical models of depression and anxiety.

Methods:

Antidepressant activity was evaluated in preliminary tests such as forced swim and tail suspension tests (FST & TST). Anti-anxiety effect of QCF-21 was investigated by employing elevated plus maze (EPM), light/dark and hole board tests. Olfactory bulbectomy (OBX) in rats was used as chronic model of depression. Mechanistic test of QCF-21 was evaluated by reserpine-induced hypothermia and 5-hydroxytryptophan (5-HTP)-induced head-twitch response.

Results:

The dose-response study revealed an initial antidepressant-like effect of QCF-21(0.25-1 mg/kg, i.p.) in the FST and TST and anxiolytic-like effect in EPM, light and dark and hole board tests. QCF-21 potentiated the 5-HTP-induced head-twitches response in mice and reversed reserpine-induced hypothermia in rats. QCF-21 significantly reversed the behavioural anomalies post-OBX in rats.

Interpretation & conclusions:

The present findings indicate the potential antidepressant-like and anxiolytic-like effects of QCF-21 at low doses in rodent behavioural models of depression and anxiety. Further studies need to be done to understand the underlying mechanism.

Potentials of Mangifera indica in the treatment of depressive-anxiety disorders: possible mechanisms of action

BACKGROUND

Mangifera indica (Anacardiaceae) is an important herb in the traditional African and Ayurvedic medicines. The stem barks are used in the treatment of hypertension, insomnia, tumour, depression, rheumatism and as a tonic. This study was carried out to investigate antidepressant- and anxiolytic-like effect of the hydroethanol stem bark extract of M. indica (HeMI) in mice.

METHODS

HeMI (12.5-100 mg/kg, p.o.) was administered 1 h before subjecting the animal to the forced swim test (FST), tail suspension test (TST) and elevated plus maze tests (EPM).

RESULTS

HeMI (12.5-100 mg/kg, p.o.) treatment produced significant reduction in immobility time [F(6.56)=8.35, p<0.001], [F(6,56)=7.55, p<0.001] in the FST and TST, respectively. Moreover, co-administration of sub-therapeutic doses of imipramine or fluoxetine with HeMI (3.125 mg/kg) elicited significant reduction in time spent immobile in the FST. However, pretreatment of mice with parachlorophenylalanine, metergoline, yohimbine or sulpiride abolished the antidepressant-like effect elicited by HeMI. In the EPM, HeMI produced significant [F(5,42)=8.91, p<0.001] increase in open arms exploration by 75.55 % and this effect was blocked by pretreatment of mice with flumazenil or metergoline.

CONCLUSIONS

Findings from this study showed antidepressant-like effect of M. indica through interaction with 5-HT2 receptor, α2-adrenoceptor and dopamine D2-receptors. Also, an anxiolytic-like effect through its affinity for 5-HT2 and benzodiazepine receptors. Hence, M. indica could be a potential phytotherapeutic agent in the treatment of mixed anxiety-depressive illness.

Antidepressant-like and toxicological effects of a standardized aqueous extract of Chrysactinia mexicana A. Gray (Asteraceae) in mice

ETHNOPHARMACOLOGICAL RELEVANCE

C. mexicana A. Gray (Asteraceae) is a native of North America plant. In Mexico׳s folk medicine it is used for the fever, rheumatism and as a diuretic, antispasmodic, general tonic or adaptogenic herb, and as a stimulant agent. The aim of the study was to examine the antidepressant-like properties of an aqueous extract of C. mexicana (Cm), in order to scientifically describe its potential value in the management of depressive disorders. To evaluate the acute and subacute toxic effects of Cm and effects on hepatic and biochemical functions in mice.

MATERIALS AND METHODS

Antidepressant-like effects of Cm were evaluated in the Forced swimming and suspension tail tests (FST and TST), the ambulatory activity was measure in the Open Field Test (OFT), motor coordination was evaluated in the inverted screen and gyratory roller (IST and Rota-rod), the biochemical and histopathological analysis were carried out. Phytochemical studies of organic and aqueous extracts of Cm were thoroughly conducted.

RESULTS

Cm produced a significant reduction of the immobility time both FST and in TST, without affect the ambulatory activity of experimental mice. Cm did not produce any damage in the hepatic functions, nor produce any significant change in the morphological tissue of organs examined.

CONCLUSIONS

Chrysactinia mexicana induces a clear antidepressant-like effect in mice, without affect any basic functions. The consumption of this medicinal plant does not represent risk for health. The chemical analysis showed the flavonoids free and glycosides mainly.

Investigation of in vivo neuropharmacological effect of Alpinia nigra leaf extract

OBJECTIVE

To analyze in vivo neuro-pharmacological effects of Alpinia nigra as anxiety is a particular form of behavioral inhibition that occurs in response to novel environmental events.

METHODS

In present study, the extract of Alpinia nigra was evaluated for its central nervous system depressant effect using mice behavioral models, such as hole cross, open field and thiopental sodium induced sleeping time tests for its sedative properties and an elevated plus-maze test for its anxiolytic potential, respectively.

RESULTS

In anxiolytic study, the extract displayed increased percentage of entry into open arm at the dose of 400 and 200 mg/kg. The extract produced a significant (P<0.01) increase in sleeping duration and reduction of onset of sleep compared to sodium thiopental at both doses (200 and 400 mg/kg). The extract (200 and 400 mg/kg) also showed a dose-dependent suppression of motor activity and exploratory activity of the mice in both open field and hole cross test.

CONCLUSION

This study demonstrates that the treated extract has significant central nervous system depressant effect. Further studies on active constituent of the extract can provide approaches for therapeutic intervention.

Enhancing Spatial Memory: Anxiolytic and Antidepressant Effects of Tapinanthus dodoneifolius (DC) Danser in Mice

We evaluated the anxiolytic and antidepressant effects of the aqueous extract of the bark of Tapinanthus dodoneifolius (TAE) (Danser) (25, 50, and 100 mg/kg), using open field, elevated plus maze, and forced swimming tests. Effect of TAE was compared to standard drugs diazepam (2 mg/kg) and imipramine (10 mg/kg). Additionally, the same doses of TAE were evaluated on rat's memory using Y-maze task. Results showed a significant (P < 0.05; 100 mg/kg) increase in the percentage of open arm entry and the time spent in the open arms in the elevated plus maze, suggesting an anxiolytic activity of the extract. In a dose-dependant manner, TAE at 25 mg/kg significantly (P < 0.05) decreased the number of lines crossed and the rearing behavior in the open field test, suggesting its possible sedative activity. In the forced swimming test, the immobility time of the animal was significantly reduced (P < 0.05) by TAE (100 mg/kg), compared to control, and this effect was quite comparable to that of imipramine. In the Y-maze paradigm, TAE at 50 mg/kg caused a significant increase in the spontaneous alternations but with a significant decrease in exploratory behavioral pattern. Taking these results together, TAE improved the spatial memory and showed anxiolytic, antidepressant, and sedative activities. The present results support the anxiolytic and antidepressant activities of TAE and, to our knowledge, for the first time, demonstrate its enhancing effect on memory.

The antidepressant-like effect of Hedyosmum brasiliense and its sesquiterpene lactone, podoandin in mice: evidence for the involvement of adrenergic, dopaminergic and serotonergic systems

We have recently shown that the ethanol extract of the leaves of Hedyosmum brasiliense exhibits an antidepressant-like effect in the tail suspension and forced swimming tests in mice. The present study investigates the mechanisms involved in the antidepressant-like effect of H. brasiliense extract, together with the antidepressant potential of podoandin, an isolated sesquiterpenoid. H. brasiliense (50mg/kg, i.p.) and podoandin (10mg/kg, i.p.) decreased the immobility time in the forced swimming test, without any accompanying changes in ambulation in the open-field test. The anti-immobility effect of the H. brasiliense extract was prevented by pre-treating the mice with ondansetron, NAN 190, pindolol, prazosin, yohimbine, haloperidol, SCH23390, and sulpiride. On the other hand, pre-treating the mice with: p-chlorophenylalanine (4 consecutive days), ketanserin, naloxone, naltrindole, bicuculline, phaclofen, or l-arginine did not block the antidepressant-like effect of H. brasiliense. In addition, pre-treatment of the animals with methylene blue, NG-nitro-l-arginine or 7-nitroindazole, at subeffective doses, did not cause a synergistic effect with H. brasiliense extract at an effective dose in the forced swimming test. The anti-immobility effect of podoandin was also prevented by pre-treating the mice with NAN-190, ondansetron, prazosin, yohimbine, sulpiride and haloperidol. The results indicate that the antidepressant-like effect of H. brasiliense (and podoandin) is dependent on the serotonergic, noradrenergic and dopaminergic systems, but not on the GABAergic, opioid and oxidonitrergic systems.

Antidepressants: will new mechanisms of action improve poor outcomes?

Depression is one of the most common mental illnesses and has a high impact on individuals and society. Despite the numerous treatment approaches, poor response combined with the burden of residual symptoms negatively affects the overall outcome. Novel pharmacological approaches could help to address this issue.

The hydroalcoholic extract of Salvia elegans induces anxiolytic- and antidepressant-like effects in rats

Behavioral effects of a hydroalcoholic (60% ethanol) extract from the leaves of Salvia elegans Vahl (Lamiaceae) were studied in male Sprague-Dawley rats. The extract was administered intraperitoneally and its effects on spontaneous motor activity (total motility, locomotion, rearing and grooming behavior) were monitored. Putative anxiolytic and antidepressant properties of Salvia elegans were studied in the elevated plus-maze test (EPM) and in the forced swimming test (FST), respectively. Deleterious effects of Salvia elegans on learning and memory were also studied by using active and passive avoidance paradigms. The results revealed that all doses (3.12, 12.5, 25 and 50 mg/kg) of the extract caused a significant decrease in total motility, locomotion, rearing and grooming behavior. Only the dose of 12.5 mg/kg increased the exploration of the EPM open arms in a similar way to that of diazepam (1 mg/kg). In the FST, all doses of the extract induced a reduction of immobility, in a similar way to that of fluoxetine (10 mg/kg) and imipramine (12.5 mg/kg), along with a significant increase in the time spent in swimming behavior. Acquisition of active avoidance responses was disrupted by pre-treatment with the extract, but retention of a passive avoidance response was not significantly modified. These results suggest that some of the components of the hydroalcoholic extract of Salvia elegans have psychotropic properties, which deserve further investigation.

Anxiolytic and antidepressant-like effects of the hydroalcoholic extract from Aloysia polystachya in rats

Behavioral effects of a hydroalcoholic extract from leaves of Aloysia polystachya (Griseb.) Moldenke (Verbenaceae) were studied in female Sprague-Dawley rats. The extract was administered intraperitoneally and its effects on spontaneous motor activity (total motility, locomotion, rearing and grooming behavior) were monitored. Anxiolytic-like properties were studied in the elevated plus-maze (EPM) test and the possible antidepressant-like actions were evaluated in the forced swimming test (FST). The results revealed that high doses of the extract (25 and 50 mg/kg, i.p.) caused a significant decrease in total motility, locomotion, rearing and grooming behavior. All doses injected (from 1.56 to 50 mg/kg) increased the exploration of the EPM open arms in a similar way to that of diazepam (1 mg/kg, i.p.). In the FST, the extract (12.5, 25 and 50 mg/kg) was as effective as fluoxetine (10 mg/kg, i.p.) and imipramine (12.5 mg/kg, i.p.) in reducing immobility, along with a significant increase in swimming and climbing, respectively. These results suggest that some of the components of the hydroalcoholic extract of A. polystachya, such as thujone and carvone among others, may have sedative, anxiolytic and antidepressant-like properties which deserve further investigation.

Worsening of depressive symptoms prior to randomization in clinical trials: a possible screen for placebo responders?

A common practice in depression trials is to exclude patients whose depressive symptoms improve between Screen and Baseline evaluations under the assumption that they are more likely to respond to placebo. The present study investigated this contention by examining the relationship between pre-randomization changes in Hamilton depression rating scale (HAMD) scores to post-randomization placebo response and drug-placebo separation. Four randomized, double-blind, placebo-controlled trials (active medication=fluoxetine or paroxetine) were conducted in outpatients with Major Depressive Disorder using a novel design in which a depressive severity inclusion criterion (HAMD >/= 22) was utilized only at Screen. Patients with no change or minimal (1 point) improvement on the HAMD between Screen and Baseline had the lowest placebo response and the best drug-placebo separation. Patients with pre-randomization improvement of 2 points or greater had moderately higher placebo response and poorer drug-placebo separation. Patients who worsened between Screen and Baseline showed the highest placebo response and the poorest drug-placebo separation. There were no obvious differences in demographic variables between the groups which could account for the findings. In our original analyses 3/4 studies failed to show significant drug-placebo separation. When only patients with no change or pre-randomization improvement of 1 point were used in the analyses, 3/4 studies showed significant drug-placebo separation while the other study approached significance, p < 0.07. These results suggest that pre-randomization changes in HAMD scores may predict post-randomization placebo response and drug-placebo separation. Further, pre-randomization increases in HAMD scores (i.e., worsening) may be the best predictor of heightened placebo responding and poor drug placebo separation.

Toxicity of kava pyrones, drug safety and precautions--a case study

Kava pyrones have been sold in Germany as OTC anxiolytics until June 2002, when all preparations with a kava pyrone content of more than 10(-4) of a homeopathic stock solution were withdrawn. Other countries in which kava pyrones have been used as anxiolytics, namely GB and the USA, have not followed suit. Kava pyrone anxiolytics have been positively reviewed by the Cochrane Collaboration; also newer German clinical studies have indicated pharmacological anxiolysis at the recommended doses. To use the first choice of treatment, psychotherapy, for all uncomplicated cases of pathological fear does not appear to be realistic. Current data about kava pyrone toxicity are unclear. Judging from the few well documented cases of kava pyrone hepatotoxicity (appr. 2 out of 36) in Germany and Switzerland, an immunologically mediated idiosyncratic mechanism appears to be most likely, especially at higher doses, whereas a direct toxic mechanism is much less likely. No direct results are available for the incidence of kava pyrone-related adverse drug effects. From spontaneously reported cases the incidences of adverse drug reactions cannot be obtained, a rough estimation indicates the incidence of hepatotoxicity to be comparable to those of benzodiazepines. Taken together, the withdrawal of kava pyrone-based anxiolytics appears to be an ill founded over-reaction given the lack of superior therapeutic alternatives. Neither the case evaluations presented by the BfArM (Bundesamt für Arzneimittel und Medizinprodukte = Federal Office for Drugs and Medical Products) nor the complete rejection of proof for therapeutic efficacy of kava pyrone anxiolytics are scientifically well founded.