A cycloartane glycoside derived from Actaea racemosa L. modulates GABAA receptors and induces pronounced sedation in mice.

23-O-Acetylshengmanol 3-O-ß-D-xylopyranoside (Ac-SM) isolated from Actaea racemosa L.-an herbal remedy for the treatment of mild menopausal disorders-has been recently identified as a novel efficacious modulator of GABAA receptors composed of α1-, ß2-, and γ2S-subunits. In the present study, we analyzed a potential subunit-selective modulation of GABA-induced chloride currents (IGABA) at GABA concentrations eliciting 3-8% of the maximal GABA response (EC3-8) through nine GABAA receptor isoforms expressed in Xenopus laevis oocytes by Ac-SM with two-microelectrode voltage clamp and behavioral effects 30 minutes after intraperitoneal application in a mouse model. Efficacy of IGABA enhancement by Ac-SM displayed a mild α-subunit dependence with α2ß2γ2S (maximal IGABA potentiation [Emax] = 1454 ± 97%) and α5ß2γ2S (Emax = 1408 ± 87%) receptors being most efficaciously modulated, followed by slightly weaker IGABA enhancement through α1ß2γ2S (Emax = 1187 ± 166%), α3ß2γ2S (Emax = 1174 ± 218%), and α6ß2γ2S (Emax = 1171 ± 274%) receptors and less pronounced effects on receptors composed of α4ß2γ2S (Emax = 752 ± 53%) subunits, whereas potency was not affected by the subunit composition (EC50 values ranging from α1ß2γ2S = 35.4 ± 12.3 µM to α5ß2γ2S = 50.9 ± 11.8 µM). Replacing ß2- with ß1- or ß3-subunits as well as omitting the γ2S-subunit affected neither efficacy nor potency of IGABA enhancement by Ac-SM. Ac-SM shifted the GABA concentration-response curve toward higher GABA sensitivity (about 3-fold) and significantly increased the maximal GABA response by 44 ± 13%, indicating a pharmacological profile distinct from a pure allosteric GABAA receptor modulator. In mice, Ac-SM significantly reduced anxiety-related behavior in the elevated plus maze test at a dose of 0.6 mg/kg, total ambulation in the open field test at doses ≥6 mg/kg, stress-induced hyperthermia at doses ≥0.6 mg/kg, and significantly elevated seizure threshold at doses ≥20 mg/kg body weight. High efficacy and long biologic half-life of Ac-SM suggest that potential cumulative sedative side effects upon repetitive intake of A. racemosa L. preparations might not be negligible.

GPER1 (GPR30) knockout mice display reduced anxiety and altered stress response in a sex and paradigm dependent manner.

The putative estrogen receptor GPER1 (the former orphan receptor GPR30) is discussed to be involved in emotional and cognitive functions and stress control. We recently described the induction of anxiety-like effects by the GPER1 agonist G-1 upon systemic injection into mice. To contribute to a better understanding of the role of GPER1 in anxiety and stress, we investigated germ-line GPER1 deficient mice. Our experiments revealed marked differences between the sexes. A mild but consistent phenotype of increased exploratory drive was observed in the home cage, the elevated plus maze and the light-dark choice test in male GPER1 KO mice. In contrast, female GPER1-KO mice displayed a less pronounced phenotype in these tests. Estrous-stage dependent mild anxiolytic-like effects were observed solely in the open field test. Notably, we observed a strong shift in acute stress coping behavior in the tail suspension test and basal corticosterone levels in different phases of the estrous cycle in female GPER1-KO mice. Our data, in line with previous reports, suggest that GPER1 is involved in anxiety and stress control. Surprisingly, its effects appear to be stronger in male than female mice.

Ablation of Sphingosine 1-Phosphate Receptor Subtype 3 Impairs Hippocampal Neuron Excitability In vitro and Spatial Working Memory In vivo.

Understanding the role of the bioactive lipid mediator sphingosine 1-phosphate (S1P) within the central nervous system has recently gained more and more attention, as it has been connected to major diseases such as multiple sclerosis and Alzheimer's disease. Even though much data about the functions of the five S1P receptors has been collected for other organ systems, we still lack a complete understanding for their specific roles, in particular within the brain. Therefore, it was the aim of this study to further elucidate the role of S1P receptor subtype 3 (S1P3) in vivo and in vitro with a special focus on the hippocampus. Using an S1P3 knock-out mouse model we applied a range of behavioral tests, performed expression studies, and whole cell patch clamp recordings in acute hippocampal slices. We were able to show that S1P3 deficient mice display a significant spatial working memory deficit within the T-maze test, but not in anxiety related tests. Furthermore, S1p3 mRNA was expressed throughout the hippocampal formation. Principal neurons in area CA3 lacking S1P3 showed significantly increased interspike intervals and a significantly decreased input resistance. Upon stimulation with S1P CA3 principal neurons from both wildtype and [Formula: see text] mice displayed significantly increased evoked EPSC amplitudes and decay times, whereas rise times remained unchanged. These results suggest a specific involvement of S1P3 for the establishment of spatial working memory and neuronal excitability within the hippocampus.

Activation of the G-protein-coupled receptor GPR30 induces anxiogenic effects in mice, similar to oestradiol.

RATIONALE: The influence of ovarian hormones on behaviour is well accepted, and oestrogen replacement therapy has proven to be beneficial in several cases of menopausal mood disorders. However, there are also some adverse effects of such a therapy, like anxiety and dysphoria. In fact, some women feel better at low levels of oestrogen and worse when levels fluctuate. Still, it is unclear which receptors might mediate negative emotional effects. OBJECTIVES: The aim of this study was to identify which oestrogen receptor(s) are capable of mediating negative emotional effects and, therefore, may represent candidates responsible for the adverse side effects observed in oestrogen replacement therapy. RESULTS: We provide evidence from mouse behavioural tests that oestrogen-induced anxiogenic-like effects might be mediated, at least in part, by the G protein-coupled receptor GPR30. The short-term application of specific agonists against the alpha and beta oestrogen receptors did not result in marked behavioural changes. In contrast, the specific stimulation of GPR30 in male and ovariectomized female mice induced anxiogenic effects. The anxiogenic effects induced by the specific GPR30 agonist G-1 were comparable (and non-accumulative) to those observed after low doses of the general oestrogen receptor agonist 17b-oestradiol in male mice, thereby reflecting the behavioural changes observed in intact female mice during early pro-oestrus. CONCLUSIONS: Our data suggest that GPR30 induces acute anxiogenic effects of oestrogen in rodents. It is tempting to speculate that a potential imbalance in the expression of the anxiolytic beta oestrogen receptor and the anxiogenic GPR30 may also be involved in the negative symptoms of oestrogen replacement therapy in humans.

Influence of sex and genetic background on anxiety-related and stress-induced behaviour of prodynorphin-deficient mice.

The role of dynorphin/kappa opioid receptors in epilepsy and addiction are well accepted, but their function in emotional control is not yet fully understood. Data obtained from different strains of prodynorphin (Pdyn)- and kappa opioid receptor (KOP)-deficient mice do not provide a consistent picture of the functions of Dyn/KOP in anxiety, suggesting the influence of testing conditions and/or genetic background. Therefore, we investigated the behaviour and neurochemistry of male and female Pdyn KO mice on the balb/c and C57Bl/6N background. Consistent with our results obtained from male mice on the C57bl/6N background, we observed a less anxious phenotype in the elevated plus maze, open-field and light-dark test in male mice on the balb/c background. Female mice on the balb/c background also displayed less anxiety like behaviour; however these data reflect high trait anxiety and inter-individual differences. In contrast, female mice on the C57Bl/6N background displayed low trait anxiety and a paradigm-dependent reduction of anxiety. No differences were observed in the forced swim test, while balb/c Pdyn KO mice displayed prolonged immobility in the tail suspension test. In line with our previous results, we observed reduced CRH mRNA in the central amygdala in all groups of mice. In contrast, the recently observed CRH mRNA reduction in the hypothalamic paraventricular nucleus appears restricted to male, but not female mice. Our data support previous data suggesting a pronounced impact of endogenous prodynorphin-derived peptides on anxiety. Moreover, our data support the idea that the less anxious phenotype manifests only at elevated stress levels.