Anxiolytic Effects In Animal Models Research Articles

Combretum lanceolatum extract reverses anxiety and seizure behavior in adult zebrafish through GABAergic neurotransmission: an in vivo and in silico study

Combretaceae are reported in the literature for presenting neuroprotective and anxiolytic effects in animal models. Combretum lanceolatum Pohl. has few scientific reports on its pharmacological effects. The aim of this study was to evaluate the anxiolytic and anticonvulsant effects of the ethanol extract from the leaves of C. lanceolatum Pohl. (EtFoCl) and its possible mechanism of GABAergic action in adult zebrafish. EtFoCl was subjected to determination of the total phenol concentration, identification of phytochemical flavonoids by HPLC and in vitro antioxidant activity test, open field test and 96-hour acute toxicity in zebrafish. Anxiolytic doses were tested for pentylenetetrazole-induced seizures in adult zebrafish. To study the mechanisms of action, molecular docking simulations were performed between the main phytochemicals and the GABAA receptor (anxiolytic activity) and carbonic anhydrase II (anticonvulsant). The non-toxic doses that caused motor impairment were assessed in acute and chronic anxiety using the light and dark test. EtFoCl had altered the animals’ locomotion, presenting an effect similar to the anxiolytic and anticonvulsant. These effects were prevented with flumazenil (GABAA antagonist). The phytochemicals homoorientin and quercetin-3-O-galactoside coupling in a region close to that of the inhibitor diazepam (GABAA receptor). Regarding the anticonvulsant mechanism, Homoorientina and Isovitexina were identified as the most favorable for the complex form with the carbonic anhydrase enzyme. C. lanceolatum has pharmacological potential for the treatment of acute and chronic anxiety and seizures, which can be partially explained by an interaction with the GABAA receptor. Communicated by Ramaswamy H. Sarma

Anxiolytic Effects of the Methanolic Extract of <i>Bacopa monniera</i> in Mice

Bacopa monniera Linn. or Brahmi, a plant in the family Scrophulariaceae, is used as a traditional medicine for memory improvement, dementia like anxiety, depression, epilepsy etc. for a long time in Bangladesh. This study evaluated the anxiolytic effects of the methanolic extract of B. monniera (MEBM) in animal models of anxiety. For the further tests and phytochemical screening, the whole plant of B. monniera extracted following maceration method. The extract was evaluated for anxiolytic activity using light/dark box, elevated plus maze, marble burying and rota rod tests in mice at the doses of 50, 100, and 200 mg/kg body weight. Diazepam (1.0 mg/kg), an anxiolytic drug used as standard drug. MEBM showed a strong and dose-dependent anxiolytic effects in animal models of anxiety. MEBM significantly increased the time spent in the light compartment, the latency time, and the entries of open arms in light/dark and elevated plus maze tests. In addition, MEBM also significantly decreased the number of buried marbles in marble burying test and increased the time of performance in rota rod test (p < 0.05). These were the major findings of this study. Therefore, our results reported that MEBM possesses anxiolytic effects in animal models of anxiety that support the traditional use of this plant as a potent agent to combat anxiety.

Neural cell adhesion molecule peptide mimetics modulate emotionality: pharmacokinetic and behavioral studies in rats and non-human primates.

Recent evidence highlights the fibroblast growth factor (FGF) family in emotion modulation. Although ligands that activate FGF receptors have antidepressant and anxiolytic effects in animal models, FGF ligands have a broad range of actions both in the brain and the periphery. Therefore, identifying molecular partners that may function as allosteric modulators could offer new avenues for drug development. Since neural cell adhesion molecule (NCAM) activates FGF receptors, we asked whether peripherally administered NCAM peptide mimetics penetrate the brain and alter the behavior of standardized tests that have predictive validity for drug treatments of anxiety or depression. The NCAM peptide mimetic, plannexin, acutely increased and chronically decreased anxiety, but did not have antidepressant effects in rats. Another NCAM peptide mimetic, FGLL, had acute anxiogenic effects and chronic antidepressant effects in rats. A related NCAM peptide mimetic, FGLS, had antidepressant effects without modulating anxiety-like behavior, and these antidepressant effects were blocked by an AMPA receptor antagonist. Cisternal cerebrospinal fluid (CSF) levels of FGLs correlated with blood plasma levels in rats and non-human primates, and CSF-to-blood ratios of FGLS were comparable in both species. Results indicate that NCAM peptide mimetics penetrate the brain and support the suggestion that FGLS may be a candidate for further development as a novel treatment for major depressive disorder in humans.

Anxiolytic effects of ascorbic acid and ketamine in mice

Some studies have demonstrated that ascorbic acid, similarly to ketamine, exhibits antidepressant-like effects mediated, at least in part, by modulation of the glutamatergic system. Despite the involvement of glutamatergic system in the pathophysiology of anxiety disorders, the ability of ascorbic acid and ketamine to elicit anxiolytic effects in animal models remains to be established. Therefore, this study investigated the effects of a single administration of ascorbic acid, ketamine or diazepam (positive control) in different animal models of anxiety. Mice were treated with ascorbic acid (1, 3 and 10 mg∕kg, p.o.), ketamine (1 and 10 mg∕kg, i.p.) or diazepam (2 mg∕kg, p.o) and their behavioral responses were assessed in the elevated plus maze, open field test (OFT), ligh∕dark preference test and marble burying test. Ascorbic acid increased total time spent in the open arms of elevated plus maze, increased total time in the center of the OFT, decreased rearing responses, increased the latency to grooming, decreased the rostral grooming, but did not affect body grooming. Furthermore, ascorbic acid increased the latency time and total time in light area in the ligh∕dark preference test, but did not affect the performance of mice in the marble burying test. Ketamine demonstrated an anxiolytic-like effect in elevated plus maze, OFT, and ligh∕dark preference test. Diazepam exhibited an anxiolytic-like effect in all the behavioral tests. Altogether, the results indicate the potential anxiolytic effect of ascorbic acid and ketamine, providing a possible new avenue for the management of anxiety-related disorders.

Neurotensin NTS1 and NTS2 receptor agonists produce anxiolytic-like effects in the 22-kHz ultrasonic vocalization model in rats

Neurotensin is a neuropeptide neurotransmitter that interacts with multiple neurotransmitter systems, including those regulating amygdalar function, via NTS1 and NTS2 receptors. Both receptors are expressed in the amygdala and agonists for NTS1 or NTS2 receptors have exhibited anxiolytic effects in animal models. Systemic adminstration of NTS1 receptor agonist PD149163 was recently shown to reduce footshock conditioned 22-kHz ultrasonic vocalizations in rats, suggesting that PD149163 produced an anxiolytic effect. The effects that neurotensin may have or a selective NTS2 receptor agonist may have on 22-kHz vocalizations has yet to be examined. The current study evaluated the effects of intracerebroventricularly administered neurotensin (0.1–10.0μg), PD149163 (0.1–10.0ng), or the NTS2 receptor agonist JMV-431 (0.1–1.0μg) on footshock conditioned 22-kHz vocalizations in male Wistar rats. Neurotensin, PD149163, and JMV-431 all significantly reduced the number 22-kHz calls. No changes in call duration were found, suggesting that non-specific drug effects do not account for the reductions in 22-kHz calls. These data support anxiolytic effects produced by activation of NTS1 or NTS2 receptors, and suggest that neurotensin plays a natural role in the expression of conditioned USVs. These data suggest that both receptor subtypes are putative pharmacologic targets.

Evaluation of anxiolytic potency of essential oil and S-(+)-linalool from Cinnamomum osmophloeum ct. linalool leaves in mice

Cinnamomum osmophloeum ct. linalool (土肉桂 tǔ ròu guì) is one chemotype of the indigenous cinnamons in Taiwan. This study examined the anxiolytic potency of leaf essential oil (LEO) from C. osmophloeum ct. linalool and its main constituent on 4-week ICR mice using an open field test (OFT), a light–dark test (LDT) and an elevated plus maze test (EPT). After oral administration of corn oil, LEO (250 mg/kg and 500 mg/kg), S-(+)-linalool (500 mg/kg), R-(−)-linalool (500 mg/kg), and trazodone hydrochloride (75 mg/kg) for 14 days, the anxiolytic effects on mice behavior were evaluated. The results showed that LEO from C. osmophloeum ct. linalool leaves and S-(+)-linalool can significantly increase the time mice remained in the center area of the OFT, the illuminated area of the LDT and the open arms of the EPT without any side effects affecting motor activity, indicating excellent anxiolytic responses. Furthermore, results from the measurements of monoamines in mice brain revealed decreases in serotonin, dopamine, and norepinephrine, which are consistent with their anxiolytic effects in animal models. The findings obtained suggest that LEO from C. osmophloeum ct. linalool and its major compound, S-(+)-linalool, possess anxiolytic properties without any side effects and thus support their potential use in treatment of anxiety disorders.

Involvement of arginine vasopressin and V1b receptor in alcohol drinking in Sardinian alcohol-preferring rats.

Recent animal studies have shown that the level of stress-responsive arginine vasopressin (AVP) gene expression in the amygdala is increased during early withdrawal from long-term heroin or cocaine administration. The selective AVP V1b receptor antagonist SSR149415 (capable of exerting antidepressant-like and anxiolytic effects in animal models) also blocked stress-induced reinstatement of drug-seeking behavior. This study was undertaken to investigate the effects of alcohol and to determine whether (i) there are genetically determined differences in basal AVP mRNA levels in the medial/central amygdala (Me/CeA) and medial hypothalamus (MH) between selectively bred Sardinian alcohol-preferring (sP) and alcohol-nonpreferring (sNP) rats; (ii) the AVP mRNA levels are altered by long-term alcohol drinking in sP rats; and (iii) the V1b receptor antagonist SSR149415 alters alcohol drinking in sP rats. In Experiment 1, AVP mRNA levels were measured in the Me/CeA and MH of alcohol-naïve sP and sNP rats, and sP rats exposed to the standard, homecage 2-bottle "alcohol versus water" choice regimen 24 h/d for 17 days. In Experiment 2, SSR149415 (0, 3, 10, or 30 mg/kg; intraperitoneal) was acutely administered 30 minutes before lights off to alcohol-experienced sP rats. Alcohol, water, and food intake were monitored 6 and 24 hours later. We found higher basal AVP mRNA levels in both Me/CeA and MH of alcohol-naïve sP than sNP rats; alcohol consumption decreased AVP mRNA levels in both brain regions of sP rats, suggesting genetically determined differences between the 2 rat lines and in the effects of alcohol drinking in sP rats. Acute treatment with SSR149415 significantly reduced alcohol intake of sP rats. The stress-responsive AVP/V1b receptor system is 1 component of the neural circuitry underlying high alcohol drinking in sP rats.

Translocator Protein Ligands as Promising Therapeutic Tools for Anxiety Disorders

The Translocator protein (TSPO), formerly known as the peripheral-type benzodiazepine receptor, is an 18 kDa mitochondrial protein primarily involved in steroid biosynthesis in both peripheral and glial cells. It has been extensively reported that TSPO regulates the rate-limiting translocation of cholesterol from the outer to the inner mitochondrial membrane before its transformation by cytochrome P450(scc) into pregnenolone, which is further converted into an array of different steroids. In the brain, neurosteroids such as allopregnanolone and pregnenolone, acting as positive modulators of gamma-aminobutyric type A (GABA(A)) receptors, exert anxiolytic activity. Specific ligands targeting TSPO increase neurosteroid production and for this reason they have been suggested to play an important role in anxiety modulation. Unlike benzodiazepines (Bzs), which represent the most common anti-anxiety drugs administered around the world, selective TSPO ligands have shown anxiolytic effects in animal models without any of the side effects associated with Bzs. Therefore, specific TSPO ligands that are able to promote neurosteroidogenesis may represent the future of therapeutic treatment of anxiety disorders. Furthermore, TSPO expression levels are altered in several different psychiatric disorders in which anxiety is the main symptom. This article reviews the primary and patent literature over the last decade concerning the development of novel TSPO ligands that have resulted effective in various models of anxiety, taking into special consideration their structure-activity relationships.

Translocator Protein (18 kD) as Target for Anxiolytics Without Benzodiazepine-Like Side Effects

Most antianxiety drugs (anxiolytics) work by modulating neurotransmitters in the brain. Benzodiazepines are fast and effective anxiolytic drugs; however, their long-term use is limited by the development of tolerance and withdrawal symptoms. Ligands of the translocator protein [18 kilodaltons (kD)] may promote the synthesis of endogenous neurosteroids, which also exert anxiolytic effects in animal models. Here, we found that the translocator protein (18 kD) ligand XBD173 enhanced gamma-aminobutyric acid-mediated neurotransmission and counteracted induced panic attacks in rodents in the absence of sedation and tolerance development. XBD173 also exerted antipanic activity in humans and, in contrast to benzodiazepines, did not cause sedation or withdrawal symptoms. Thus, translocator protein (18 kD) ligands are promising candidates for fast-acting anxiolytic drugs with less severe side effects than benzodiazepines.

The anxiolytic-like effects of allopregnanolone vary as a function of intracerebral microinfusion site: the amygdala, medial prefrontal cortex, or hippocampus

Allopregnanolone is a 5alpha-reduced metabolite of progesterone that potentiates gamma-aminobutyric acid type-A (GABA(A)) receptor activity and produces anxiolytic effects in animal models. Little is, however, known about the brain regions that mediate its anxiolytic effects. In this study Sprague-Dawley rats were microinfused with allopregnanolone into the amygdala, medial prefrontal cortex, or hippocampus--brain regions that have been previously implicated in the control of anxiety in animal models. After the microinfusion, the animals were tested on the elevated plus-maze and the shock-probe burying test. In the amygdala, allopregnanolone produced anxiolytic-like effects in both tests; in the medial prefrontal cortex, allopregnanolone produced anxiolytic effects restricted to the plus-maze test; in the hippocampus, allopregnanolone was ineffective in both tests. The results were discussed in terms of differences in the control of specific fear reactions within subregions of each brain area, differences in the 'sensitivity' of behavioral tests to the anxiolytic effects of allopregnanolone, and finally, regional differences in the subunit composition of GABA(A) receptors and their possible relationship to the relative efficacy of steroidal and nonsteroidal GABA(A) agonists.

Peptidic delta opioid receptor agonists produce antidepressant-like effects in the forced swim test and regulate BDNF mRNA expression in rats

Systemically active, nonpeptidic delta opioid receptor agonists have been shown to produce antidepressant and anxiolytic effects in animal models in rodents. In addition, delta agonists have been shown to increase expression of brain-derived neurotrophic factor (BDNF) mRNA, an effect of some antidepressants, which may be important for the clinical efficacy of antidepressant drugs. The present study examined whether a variety of peptidic delta agonists, DPDPE, JOM-13, a systemically active derivative of DPDPE, deltorphin II, and H-Dmt-Tic-NH-CH 2-Bid could produce convulsions and antidepressant-like effects in the forced swim test. In addition, some of these compounds were examined for their influence on BDNF mRNA expression. All four agonists dose-dependently decreased immobility in the forced swim test, indicating an antidepressant-like effect. Only JOM-13 produced convulsions at doses required for antidepressant-like effects. In addition, DPDPE increased BDNF mRNA expression, as measured by in situ hybridization, in the frontal cortex. The antidepressant-like effect of the agonists in the forced swim test and the increase in BDNF mRNA expression produced by DPDPE were blocked by the delta antagonist naltrindole. Therefore, activation of the delta receptor by centrally administered peptidic agonists and intravenously administered JOM-13 produces behavioral antidepressant-like effects without producing convulsions, and some peptidic agonists can increase BDNF mRNA expression, however, not as consistently as the systemically active nonpeptidic agonists.

Neurosteroid secretion in panic disorder

Evidence that neurosteroids have anxiolytic effects in animal models of anxiety has suggested that alterations of neurosteroid secretion might be implicated in the pathogenetic mechanisms of anxiety disorders in humans. In 25 female patients with panic disorder (PD) and 11 healthy female controls, we measured plasma concentrations of progesterone (PROG), pregnenolone (PREG), allopregnanolone (3α,5α-tetrahydroprogesterone=3α,5α-THPROG), dehydroepiandrosterone (DHEA) and tetrahydrodeoxycorticosterone (3α,5α-THDOC) during a drug-free month and during the following month of paroxetine therapy. The neurosteroids were measured during the early follicular phase, the mid-luteal phase and the premenstrual phase of both months (days 7, 22 and 27 from the beginning of the cycle). Significantly higher levels in patients than controls were found in PROG during the mid-luteal phase of both months, PREG in the premenstrual phase in the drug-free month, 3α,5α-THPROG during the follicular phase of the drug-free month and during the premenstrual phase of the therapy month, and 3α,5α-THDOC during the premenstrual phases of both months. DHEA levels did not differ in patients and controls. These results suggest that neurosteroids in PD are hypersecreted, possibly as an attempt to counteract the anxiogenic underlying hyperactivity of the hypothalamo-pituitary-adrenal axis and to improve a reduced GABA A receptor sensitivity.

Valproate treatment of panic disorder and lactate-induced panic attacks

Several lines of evidence suggest that the anticonvulsant drug valproate may have antipanic properties: (1) It enhances γ-aminobutyric acid activity in the brain; (2) it has anxiolytic effects in animal models of anxiety; and (3) it has been reported to be effective in panic disorder in several preliminary studies; however, valproate has not been studied in the prevention of lactate-induced panic attacks. Sixteen patients with panic disorder underwent a lactate infusion followed by a 28-day treatment period with valproate and subsequent rechallenge with lactate. Response was measured by change in panic attack frequency and Hamilton Anxiety Scale (HAS) scores and by the ability of valproate to block lactate-induced panic on rechallenge. Of the 14 patients completing the 28-day trial, 10 (71%) experienced a greater than 50% reduction in the weekly frequency of panic attacks. Six (43%) had complete remission. HAS scores dropped significantly from a baseline mean of 30.8 ± 9.4 (SD) to 12.6 ± 7 after 4 weeks of treatment. Valproate blocked reinduction of panic symptoms on lactate rechallenge in 10 (83%) of 12 patients who had initially experienced panic symptoms on initial infusion. The significant reduction in spontaneous panic attacks and the blockade of lactate-induced panic symptoms by valproate support earlier studies suggesting that the drug may be an effective treatment for panic disorder.