Clove volatile oil-loaded nanoemulsion reduces the anxious-like behavior in adult zebrafish.

BACKGROUND: Clove volatile oil (CVO) and its major compound, eugenol (EUG), have anxiolytic effects, but their clinical use has been impaired due to their low bioavailability. Thus, their encapsulation in nanosystems can be an alternative to overcome these limitations. OBJECTIVES: This work aims to prepare, characterize and study the anxiolytic potential of CVO loaded-nanoemulsions (CVO-NE) against anxious-like behavior in adult zebrafish (Danio rerio). METHODS: The CVO-NE was prepared using Agaricus blazei Murill polysaccharides as stabilizing agent. The drug-excipient interactions were performed, as well as colloidal characterization of CVO-NE and empty nanoemulsion (B-NE). The acute toxicity and potential anxiolytic activity of CVO, EUG, CVO-NE and B-NE against adult zebrafish models were determined. RESULTS: CVO, EUG, CVO-NE and B-NE presented low acute toxicity, reduced the locomotor activity and anxious-like behavior of the zebrafish at 4 - 20 mg kg-1. CVO-NE reduced the anxious-like behavior of adult zebrafish without affecting their locomotor activity. In addition, it was demonstrated that anxiolytic activity of CVO, EUG and CVO-NE is linked to the involvement of GABAergic pathway. CONCLUSION: Therefore, this study demonstrates the anxiolytic effect of CVO, in addition to providing a new nanoformulation for its administration.

Anti-aversive effect of 2-arachidonoylglycerol in the dorsolateral periaqueductal gray of male rats in contextual fear conditioning and Vogel tests.

The endocannabinoid system modulates the stress coping strategies in the dorsolateral periaqueductal grey (dlPAG). The most relevant endocannabinoids, anandamide and 2-arachidonoylglycerol (2-AG) exert inhibitory control over defensive reactions mediated by the dlPAG. However, the protective role of anandamide is limited by its lack of effect in higher concentrations. Thus, the 2-AG emerges as a complementary target for developing new anxiolytic compounds. Nevertheless, the role of 2-AG on stress responsivity may vary according to the nature of the stimulus. In this study, we verified whether the dlPAG injection of 2-AG or inhibitors of its hydrolysis induce anxiolytic-like effects in male Wistar rats exposed to behavioral models in which physical stress (mild electric shock) is a critical component, namely the contextual fear conditioning test (CFC) and the Vogel conflict test (VCT). We also investigated the contribution of cannabinoid receptor type 1 (CB1) and type 2 (CB2) in such effects. The facilitation of 2-AG signaling in the dlPAG reduced contextual fear expression and exhibited an anxiolytic-like effect in the VCT in a mechanism dependent on activation of CB1 and CB2. However, the VCT required a higher dose than CFC. Further, the monoacylglycerol inhibitors, which inhibit the hydrolysis of 2-AG, were effective only in the CFC. In conclusion, we confirmed the anti-aversive properties of 2-AG in the dlPAG through CB1 and CB2 mechanisms. However, these effects could vary according to the type of stressor and the anxiety model employed.

Neonatal Serotonin Depletion Induces Hyperactivity and Anxiolytic-like Sex-Dependent Effects in Adult Rats.

The serotoninergic system plays an important role in the ontogeny of the mammalian central nervous system, and changes in serotonin production during development may lead to permanent changes in brain cytoarchitecture and function. The present study investigated the programming effects of neonatal serotonin depletion on behavior and molecular components of the serotoninergic system in adult male and female rats. Subcutaneous para-chlorophenylalanine (pCPA) administration (100 mg kg-1) was performed daily on postnatal days 8-16 to deplete brain serotonin content. During adulthood, elevated plus-maze, open field, social interaction, forced swimming, and food, saline, and sucrose intake tests were performed. Relative expression of serotonin neurotransmission components in several brain areas was determined by qPCR. Additionally, serotonin immunofluorescence and neuropeptide mRNA expression were assessed in dorsal raphe (DRN) and paraventricular (PVN) nuclei, respectively. Rat performance in behavioral tests demonstrated a general increase in locomotor activity and active escape behavior as well as decreased anxiety-like behavior after neonatal brain serotonin depletion. The behavioral programming effects due to neonatal serotonin depletion were more pronounced in females than males. At the gene expression level, the mRNA of Tph1 and Tph2 were lower in DRN while Htr2c was higher in the amygdala of pCPA-treated males, while Htr1a, Htr2c, Oxt, Avp, Crh, and Trh were not different in any treatments or sex in PVN. The results indicate that neonatal serotonin depletion has long-term consequences on locomotion and anxiety-like behavior associated with long-lasting molecular changes in the brain serotoninergic system in adult rats.

Anxiolytic and panicolytic-like effects of environmental enrichment seem to be modulated by serotonin neurons located in the dorsal subnucleus of the dorsal raphe.

In a previous study, we showed that exposure of rats to a one-week environmental enrichment (EE) protocol decreases elevated T-maze (ETM) avoidance responses, an anxiolytic-like effect, without altering escape reactions, in clinical terms related to panic disorder. These anxiolytic-like effects were followed by decreased delta FosB-immunoreactivity (delta FosB-ir) in the cingulate cortex, dorsolateral and intermediate lateral septum, hippocampus (cornus of Ammon), anterior and dorsomedial hypothalamus, medial and basolateral amygdala and ventral region of the dorsal raphe nucleus. The purpose of the present study was to further investigate behavioral and neurophysiological alterations induced by EE exposure. For that, in a first experiment we verified if increasing the time of exposure to the same EE protocol used in our previous study (from one to two weeks) altered male Wistar rats' ETM escape responses. All animals were tested in an open field, immediately after the ETM, for locomotor activity assessment. Since anxiety and panic-related reactions have been associated to the functioning of specific subnuclei of the dorsal raphe nucleus (DR), we also evaluated delta FosB-ir in serotonergic cells of DR regions. At last, we analyzed plasma corticosterone levels in animals submitted to EE and to standard housing. Results showed that a two-week exposure to EE decreases both ETM avoidance and escape reactions, inducing anxiolytic and panicolytic-like effects, respectively. There was also a significant decrease in the number of double staining neurons in the midrostral region of the dorsal subnucleus of the dorsal raphe. No changes in corticosterone levels, however, were observed. These results contribute to a better understanding of the effects of EE on anxiety and panic-related responses.

Role of dorsal raphe nucleus GHS-R1a receptors in the regulation of inhibitory avoidance and escape behaviors in rats.

Ghrelin is a recently discovered peptide, mainly produced in the stomach and involved in body's energy-maintenance processes. Ghrelin exerts its actions by activating the growth hormone secretagogue receptor (GHS-R). Recent analyses indicate that ghrelin targets the brain to regulate a wealth of functions, including behavioral responses that have been associated with stress and anxiety mechanisms. In this context, evidence shows the presence of GHS-R receptors in the dorsal raphe nucleus (DRN), the main source of serotonergic neurons that innervate encephalic structures involved in emotional control. Our study aims to evaluate the effects of the pharmacological manipulation of ghrelin receptors located in the DRN on the expression of the behavioral responses of Wistar rats. Such responses were assessed in the elevated T maze (ETM), an experimental model that allows the measurement, in the same animal, of two defensive tasks, inhibitory avoidance and escape. Our results showed that the intra-DRN infusion of ghrelin impaired the acquisition of inhibitory avoidance, an anxiolytic-like effect, and facilitated the expression of escape response in the ETM, indicating a panicogenic-like effect. The intra-DRN administration of the ghrelin receptor (GHS-R1a) antagonist PF-04628935 did not alter the behavioral tasks assessed in the ETM. Finally, our results revealed that intra-DRN infusions of PF-04628935 prior to the administration of ghrelin into this area neutralized the behavioral effects obtained in the ETM. Taken together, our data reveal the involvement of DRN GHS-R1a receptors in the regulation of defensive tasks that have been associated with generalized anxiety and panic disorders.

Production of biomolecules of interest to the anxiolytic herbal medicine industry in yellow passionfruit leaves (Passiflora edulis f. flavicarpa) promoted by mycorrhizal inoculation.

BACKGROUND: Our contemporary way of life has led us to consume high amounts of chemically-synthesized allopathic medicinal products and anxiolytics to which a viable alternative is the use of Passiflora-based herbal medicines with composition containing vitexin, a flavonoid with anxiolytic and antidepressant properties. Arbuscular mycorrhizal fungi (AMF) are known for enhancing the production of biomolecules, however, increase production of phytochemistry in Passiflora edulis f. flavicarpa has not been reported in the literature. Our aim was to select AMF to benefit the production of vitexin in leaves of P. edulis by inoculating seedlings in the region of roots with Acaulospora longula, Claroideoglomus etunicatum and Gigaspora albida. RESULTS: The inoculation increased the concentration of vitexin in 63.64% and the inoculation with A. longula also increased the content of flavonoids and total saponins in the leaves in relation to the control. CONCLUSION: The increase in the production of vitexin in the leaf in response to the inoculation with AMF, with emphasis to A. longula, interests the pharmaceutical industry and can generate profit to the production of yellow passionfruit-based anxiolytic herbal medicine. © 2019 Society of Chemical Industry.

Enhanced expression of heme oxygenase-1 in the locus coeruleus can be associated with anxiolytic-like effects.

Some researchers have shown that carbon monoxide (CO) plays a role in emotional behavior modulation through intracellular 3'-5'-guanosine monophosphate mechanisms in the locus coeruleus (LC). In fact, the LC region has a high expression of the heme-oxygenase (HO) enzymes, which are responsible for the production of CO. However, the physiological mechanism by which the HO-CO pathway participates in the modulation of emotional responses in the LC still needs clarification. This study evaluates whether a systemic intraperitoneal treatment is able to alter behavioral responses (in the elevated plus-maze and the light-dark box test) and the expression of the HO-1 and HO-2 enzymes in the LC. The tested treatments are acute (3h before) or chronic (twice daily for 10days) and with a carbon monoxide releaser (tricarbonyldichlororuthenium [II] dimer, or CORM-2) or with a HO-1 inducer compound (cobalt protoporphyrin IX, CoPP). The results for the elevated plus-maze show that CO-for both acute or chronic administration of either drug-ncreased the number of entries into the open arms and the percentage of time spent in the open arms. Regarding the light-dark box test, chronic treatment with either drug increased the time spent in the light compartment. Additionally, treatment with CORM-2 or CoPP, either acutely or chronically, increased HO-1 enzyme expression in the LC cells. This study shows that systemic CO treatment can promote an anxiolytic-like effect and the expression of HO-1 enzymes in LC cells.

Anxiolytic-like effect of 2-(4-((1-phenyl-1H-pyrazol-4-yl)methyl)piperazin-1-yl)ethan-1-ol is mediated through the benzodiazepine and nicotinic pathways.

In this study, we proposed the design, synthesis of a new compound 2-(4-((1-phenyl-1H-pyrazol-4-yl)methyl)piperazin-1-yl)ethan-1-ol (LQFM032), and pharmacological evaluation of its anxiolytic-like effect. This new compound was subjected to pharmacological screening referred to as Irwin test, prior to sodium pentobarbital-induced sleep, open-field and wire tests. The anxiolytic-like effect of this compound was evaluated using elevated plus maze and light-dark box tests. In addition, the mnemonic activity was evaluated through step-down test. In sodium pentobarbital-induced sleep test, LQFM032 decreased latency and increased duration of sleep. In the open-field test, LQFM032 altered behavioral parameter, that suggested anxiolytic-like activity, as increased in crossings and time spent at the center of open field. In the plus maze test and light-dark box test, the LQFM032 showed anxiolytic-like activity, increased entries and time spent on open arms, and increased in number of transitions and time spent on light area, respectively. Those effects was antagonized by flumazenil but not with 1-(2-Methoxyphenyl)-4-(4-phthalimidobutyl)piperazine (NAN-190). The LQFM032 did not alter mnemonic activity. Moreover, the anxiolytic-like activity of LQFM032 was antagonized by mecamylamine. In summary, LQFM032 showed benzodiazepine and nicotinic pathways mediated anxiolytic-like activity without altering the mnemonic activity.

Tolerance to the sedative and anxiolytic effects of diazepam is associated with different alterations of GABAA receptors in rat cerebral cortex.

The clinical use of benzodiazepines is limited by the development of tolerance to their pharmacological effects. Tolerance to each of the pharmacological actions of benzodiazepines develops at different rates. The aim of this work was to investigate the mechanism of tolerance by performing behavioral tests in combination with biochemical studies. To this end, we administered prolonged treatments of diazepam to rats for 7 or 14 days. Tolerance to the sedative effects of diazepam was detected by means of the open field test after the 7- and 14-day treatments, whereas tolerance to the anxiolytic actions of benzodiazepine manifested following only the 14-day treatment in the elevated plus maze. The cerebral cortical concentrations of diazepam did not decline after the diazepam treatments, indicating that tolerance was not due to alterations in pharmacokinetic factors. The uncoupling of GABA/benzodiazepine site interactions and an increase in the degree of phosphorylation of the GABAA receptor γ2 subunit at serine 327 in the cerebral cortex were produced by day 7 of diazepam treatment and persisted after 14 days of exposure to benzodiazepine. Thus, these alterations could be part of the mechanism of tolerance to the sedative effects of diazepam. An increase in the percentage of α1-containing GABAA receptors in the cerebral cortex was observed following the 14-day treatment with diazepam but not the 7-day treatment, suggesting that tolerance to the anxiolytic effects is associated with a change in receptor subunit composition. The understanding of the molecular bases of tolerance could be important for the development of new drugs that maintain their efficacies over long-term treatments.

Age-dependent relevance of endogenous 5-lipoxygenase derivatives in anxiety-like behavior in mice.

When 5-lipoxygenase (5-LO) is inhibited, roughly half of the CNS effect of the prototypic endocannabinoid anandamide (AEA) is lost. Therefore, we decided to investigate whether inhibiting this enzyme would influence physiological functions classically described as being under control of the endocannabinoid system. Although 5-LO inhibition by MK-886 reduced lipoxin A4 levels in the brain, no effect was found in the elevated plus maze (EPM), even at the highest possible doses, via i.p. (10 mg/kg,) or i.c.v. (500 pmol/2 µl) routes. Accordingly, no alterations in anxiety-like behavior in the EPM test were observed in 5-LO KO mice. Interestingly, aged mice, which show reduced circulating lipoxin A4 levels, were sensitive to MK-886, displaying an anxiogenic-like state in response to treatment. Moreover, exogenous lipoxin A4 induced an anxiolytic-like profile in the EPM test. Our findings are in line with other reports showing no difference between FLAP KO or 5-LO KO and their control strains in adult mice, but increased anxiety-like behavior in aged mice. We also show for the first time that lipoxin A4 affects mouse behavior. In conclusion, we propose an age-dependent relevancy of endogenous 5-LO derivatives in the modulation of anxiety-like behavior, in addition to a potential for exogenous lipoxin A4 in producing an anxiolytic-like state.

N,N'-dicyclohexylsulfamide and N,N'-diphenethylsulfamide are anticonvulsant sulfamides with affinity for the benzodiazepine binding site of the GABA(A) receptor and anxiolytic activity in mice.

A set of sulfamides designed, synthesized and evaluated against maximal electroshock seizure (MES) and pentilenetetrazol (PTZ) tests with promising results, were tested for their affinity for the benzodiazepine binding site of the GABA(A) receptor. The most active compounds, N,N'-dicyclohexylsulfamide (7) and N,N'-diphenethylsulfamide (10), competitively inhibited the binding of [(3)H]-flunitrazepam to the benzodiazepine binding site with K(i)±SEM values of 27.7±4.5µM (n=3) and 6.0±1.2µM (n=3), respectively. The behavioral actions of these sulfamides, i.p. administered in mice, were examined in the plus-maze, hole-board and locomotor activity assays. Compound 7 exhibited anxiolytic-like effects in mice evidenced by a significant increase of the parameters measured in the hole-board test (at 1 and 3mg/kg) and the plus-maze assay (at 1 and 3mg/kg). Compound 10 evidenced anxiolytic activity in the plus-maze and the hole-board tests at 1mg/kg. Locomotor activity of mice was not modified by compound 7 or 10 at the doses tested. Flumazenil, a non selective benzodiazepine binding site antagonist, was able to completely reverse the anxiolytic-like effects of these sulfamides, proving that the GABA(A) receptor is implicated in this action. Anxiety represents a major problem for people with epilepsy. The use of anxiolytic and anticonvulsant sulfamides would be beneficial to individuals who suffer from both disorders.

Central nervous system activities of two diterpenes isolated from Aloysia virgata.

Using the guide of a competitive assay for the benzodiazepine binding site in the γ-aminobutyric acid type A receptor (GABA(A)), two active diterpenes were isolated from the aerial parts of Aloysia virgata (Ruíz & Pavón) A.L. Jussieu var. platyphylla (Briquet) Moldenke. These compounds, identified as (16R)-16,17,18-trihydroxyphyllocladan-3-one (1) and (16R)-16,17-dihydroxyphyllocladan-3-one (2) on the basis of spectral data, competitively inhibited the binding of [(3)H]-FNZ to the benzodiazepine binding site with K(i)±S.E.M. values of 56±19 µM and 111±13 µM, respectively. The behavioral actions of these diterpenes, intraperitoneally (i.p.) administered in mice, were examined in the plus-maze, holeboard, locomotor activity and light/dark tests. Compound 1 exhibited anxiolytic-like effects in mice evidenced by a significant increase of the parameters measured in the holeboard test (the number of head dips at 0.3 mg/kg and 3 mg/kg, the rears at 1 mg/kg and the time spent head-dipping at 3 mg/kg), in the plus-maze assay (the percentage of open arm entries at 1 mg/kg) and in the light/dark test (the time in light and the number of transitions at 1 mg/kg). Compound 2 augmented the number of rearings in the holeboard apparatus (at 0.3 mg/kg and 1 mg/kg) and the locomotor activity (at 1 mg/kg). These results reveal the presence of neuroactive compounds in Aloysia virgata.

Wiring and volume transmission in rat amygdala. Implications for fear and anxiety.

The amygdala plays a key role in anxiety. Information from the environment reaches the amygdaloid basolateral nucleus and after its processing is relayed to the amygdaloid central nucleus where a proper anxiogenic response is implemented. Experimental evidence indicates that in this information transfer a GABAergic interface controls the trafficking of impulses between the two nuclei. Recent work indicates that interneuronal communication can take place by classical synaptic transmission (wiring transmission) and by volume transmission in which the neurotransmitter diffuses and flows through the extracellular space from its site of release and binds to extrasynaptic receptors at various distances from the source. Based on evidence from our laboratory the concept is introduced that neurotransmitters in the amygdala can modulate anxiety involving changes in fear learning and memories by effects on receptor mosaics in the fear circuits through wiring and volume transmission modes of communication.

Transmissäo pelo glutamato como alvo molecular na ansiedade / Glutamatergic neurotransmission as molecular target in anxiety

O glutamato (GLU) é o principal neurotransmissor excitatório do cérebro de mamíferos. Os receptores do GLU säo classificados em ionotrópicos ou metabotrópicos. A interferência do GLU no desenvolvimento neural, na plasticidade sináptica, no aprendizado e na memória, na epilepsia, na isquemia neural, na tolerância e na dependência a drogas, na dor neuropática, na ansiedade e na depressäo tem limitado o uso de compostos que agem nos receptores de GLU, quando existe a necessidade de açöes mais seletivas dessas drogas. Dados pré-clínicos em roedores e humanos têm mostrado que compostos que reduzem a ativaçäo do GLU, pelo bloqueio dos seus receptores ou através da reduçäo da sua liberaçäo dos terminais, produzem um perfil ansiolítico em modelos de ansiedade. A aplicaçäo desses compostos em áreas específicas do cérebro, envolvidas na mediaçäo do comportamento defensivo, tal como a substância cinzenta periaquedutal dorsal, também reproduzem o mesmo perfil ansiolítico de açäo. O conhecimento crescente acerca da neurotransmissäo pelo GLU e o desenvolvimento de compostos mais seletivos atuantes nesta neurotransmissäo, renovaram a atençäo para esse sistema neurotransmissor como alvo molecular possível para uma nova classe de drogas no tratamento de condiçöes neuropsiquiátricas. Embora incompleta, esta revisäo tenta atrair a atençäo para a importância de estudos colaborativos entre clínicos e pesquisadores de ciências básicas na geraçäo de idéias para alvos potenciais no desenvolvimento de novos compostos ansiolíticos. e desta maneira contribuir para a compreensäo das bases biológicas da ansiedade

Prolonged exposure to hypobaric hypoxia transiently reduces GABA(A) receptor number in mice cerebral cortex.

The central nervous system is severely affected by hypoxic conditions, which produce alterations in neural cytoarchitecture and neurotransmission, resulting in a variety of neuropathological conditions such as convulsive states, neurobehavioral impairment and motor CNS alterations. Some of the neuropathologies observed in hypobaric hypoxia, corresponding to high altitude conditions, have been correlated with a loss of balance between excitatory and inhibitory neurotransmission, produced by alterations in glutamatergic and GABAergic receptors. In the present work, we have studied the effect of chronic hypobaric hypoxia (506 hPa, 18 h/day x 21 days) applied to adult male mice on GABA(A) receptors from cerebral cortex, to determine whether hypoxic exposure may irreversibly affect central inhibitory neurotransmission. Saturation curves for [3H]GABA specifically bound to GABA(A) receptors in isolated synaptic membranes showed a 30% decrease in maximal binding capacity after hypoxic exposure (Bmax control, 4.70+/-0.19, hypoxic, 3.33+/-0.10 pmol/mg protein), with no effect on GABA binding sites affinity (Kd control: 159.3+/-13.3 nM, hypoxic: 164.2+/-15.1 nM). Decreased B(max) values were observed up to the 10th post-hypoxic day, returning to control values by the 15th post-hypoxic day. Pharmacological properties of GABA(A) receptor were also affected by hypoxic exposure, with a 45 to 51% increase in the maximal effect by positive allosteric modulators (pentobarbital and 5alpha-pregnan-3alpha-ol-20-one). We conclude that long-term hypoxia produces a significant but reversible reduction on GABA binding to GABA(A) receptor sites in cerebral cortex, which may reflect an adaptive response to this sustained pathophysiological state.

Molecular modeling and QSAR analysis of the interaction of flavone derivatives with the benzodiazepine binding site of the GABA(A) receptor complex.

A large number of structurally different classes of ligands, many of them sharing the main characteristics of the benzodiazepine (BDZ) nucleus, are active in the modulation of anxiety, sedation, convulsion, myorelaxation, hypnotic and amnesic states in mammals. These compounds have high affinity for the benzodiazepine binding site (BDZ-bs) of the GABA(A) receptor complex. Since 1989 onwards our laboratories established that some natural flavonoids were ligands for the BDZ-bs which exhibit medium to high affinity in vitro and anxiolytic activity in vivo. Further research resulted in the production of synthetic flavonoid derivatives with increased biochemical and pharmacological activities. The currently accepted receptor/pharmacophore model of the BDZ-bs (Zhang, W.; Koeler, K. F.; Zhang, P.; Cook, J. M. Drug Des. Dev. 1995, 12, 193) accounts for the general requirements that should be met by this receptor for ligand recognition. In this paper we present a model pharmacophore which defines the characteristics for a ligand to be able to interact and bind to a flavone site, in the GABA(A) receptor. closely related to the BDZ-bs. A model of a flavone binding site has already been described (Dekermendjian, K.; Kahnberg, P.; Witt, M. R.; Sterner, O.; Nielsen, M.; Liljerfors, T. J. Med. Chem. 1999, 42, 4343). However, this alternative model is based only on graphic superposition techniques using as template a non-BDZ agonist. In this investigation all the natural and synthetic flavonoids found to be ligands for the BDZ-bs have been compared with the classical BDZ diazepam. A QSAR regression analysis of the parameters that describe the interaction demonstrates the relevance of the electronic effects for the ligand binding, and shows that they are associated with the negatively charged oxygen atom of the carbonyl group of the flavonoids and with the nature of the substituent in position 3'.

Synthesis and preliminary pharmacological evaluation of coumestans with different patterns of oxygenation.

Five coumestans with different patterns of oxygenation in rings A and D were synthesized from resorcinol and aromatic aldehydes, and screened for their antimyotoxic activity. The most potent compound (2b, IC50 = 1 microM) was selected for study of its pharmacological profile.

Benzodiazepínicos: atualidades / Benzodiazepines: up-to-date

Este trabalho tem como objetivo fazer uma revisão dos mecanismos de ação, metabolismo, excreção, indicações, efeitos colaterais, interações medicamentosas, tolerância, dependência e síndrome de obstinência dos benzodiazepínicos, atualmente um dos fármacos mais prescritos. O conhecimento desses parâmetros torna mais segura a sua utilização, com melhor e mais eficaz resposta terapêutica.

Anxiogenic-like effects of Tagetes minuta L essential oil on T-maze and tonic immobility behaviour in domestic chicks.

In a first experiment, four doses (ranging between 0.04 and 0.45 mg/kg of body weight) of the essential oil from Tagetes minuta L. were subcutaneously injected in two-day-old chicks and a dose-response curve assessed for escape performance in a T-maze test. The 0.1, 0.25 and 0.45 mg/kg doses impaired the first escape performance suggesting an anxiogenic-like effect of the essential oil. After 3 h the same chicks were tested for a second escape performance, without being injected again, and no differences were observed compared to controls, suggesting that the essential oil did not affect retention. Furthermore, the effects of the essential oil were observed in the three sections of the T-maze apparatus. So, the performance was impaired in the isolation chamber section, suggesting the induction of increased anxiogenic behaviour, and also in the mirror section, suggesting that the social reinstatement behaviour was modified by an increased anxiety level. Changes in the principal corridor section were not observed, suggesting that the locomotor activity was not affected by these oil doses. The second escape performance was not affected in any of the T-maze sections, confirming that these doses did not affect learning ability. In a second experiment, a middle dose of the essential oil (0.25 mg/kg) increased the tonic immobility reaction in 15 days old chicks similarly to an anxiogenic dose of FG 7142 (1 mg/kg), while an anxiolytic dose of diazepam (0.08 mg/kg) did not affect this behaviour. Taken together, the present results suggest that the essential oil from Tagetes minuta L. may exert a negative modulation on the GABAergic function without affecting the learning ability.

(+/-)-1-(2,5-Dimethoxy-4-ethylthiophenyl)-2-aminopropane (ALEPH-2), a novel putative anxiolytic agent lacking affinity for benzodiazepine sites and serotonin-1A receptors.

Serotonergic behavioral responses, effects on motor activity and core temperature, and binding properties of the novel putative anxiolytic amphetamine derivative (+/-)1-(2,5-dimethoxy-4-ethylthio-phenyl)-2-aminopropane (ALEPH-2), were examined in rodents in order to elucidate the mechanism underlying its anxiolytic-like effect. After peripheral administration in rats, ALEPH-2 induced some symptoms of the serotonergic syndrome, e.g. forepaw treading and flat body posture. Additionally, a decrease in motor activity was observed. No significant effects on the number of head shakes were observed after injection, although high inter-subject variability was noted. Higher doses of ALEPH-2, in the range exhibiting anxiolytic properties (4mg/kg), elicited significant hypothermia in mice. The affinity of the drug for 5-HT2A/2C receptors ([3H]ketanserin sites) was in the nanomolar range (Ki = 173 nM), whereas for 5-HT1A, benzodiazepine sites, and GABAA receptors, the affinity was micromolar of lower. Based on these results the mechanism of action and the anxiolytic-like properties of ALEPH-2 are discussed.