Prolonging effects of Valeriana fauriei root extract on pentobarbital-induced sleep in caffeine-induced insomnia model mice and the pharmacokinetics of its active ingredients under conditions of glycerol fatty acid ester as emulsifiers.

ETHNOPHARMACOLOGICAL RELEVANCE: Valeriana plant roots have traditionally been used to treat central nervous system-related disorders in European countries. Among this genus, the Japanese Pharmacopoeia registers the dried roots of V. fauriei Briq. (VF). However, insufficient pharmacological data are available for this species. AIM OF THE STUDY: We investigated the sedative effects of VF extract in a murine caffeine-induced insomnia model as well as the active ingredients and their pharmacokinetics to determine its basic pharmacological action mechanisms under conditions glycerol fatty acid ester is used as emulsifiers. MATERIALS AND METHODS: A murine insomnia model was created by caffeine. Samples derived from the ethanol extract of VF were administered per oral (p.o.), and caffeine was injected intraperitoneally (i.p.). Pentobarbital was injected i.p. and the sleep latency and duration were measured. To confirm the mechanism of action of VF, flumazenil, a specific γ-aminobutyric acid receptor type A (GABAA receptor) antagonist, was administered (i.p.) immediately prior to the sample administration. We examined the pharmacokinetic profiles of the active ingredients in the plasma, brain, urine, and feces of mice after the administration (p.o and intravenous (i.v.)) of VF samples. RESULTS: VF extract (5 g as VF/kg, p.o.) significantly shorten sleep latency and prolonged pentobarbital-induced sleep in caffeine-induced insomnia mice, partially mediated via the GABAergic nervous system, although a higher dose (10 g as VF/kg, p.o.) was required to exhibit the significant effects in normal mice. Kessyl glycol diacetate (KGD), the main constitutive compound in VF, did not shorten sleep latency but exhibited the same sleep prolonged effect at a dose related to VF extract. The concentration of kessyl glycol 8-acetate (KG8) in the plasma was higher than that of KGD in mice treated (p.o.) with VF extract. The profiles of brain concentrations of KGD and KG8 were similar to those in the plasma, and approximately 20% of those in the plasma were distributed throughout the brain. The excretions of KGD and KG8 in urine and feces was slightly detected, and an unknown large peak related to KG8 was detected in the urine of mice administered with VF extract by HPLC-MS/MS analysis. CONCLUSIONS: VF exhibits more sedative effects under stressed conditions, such as insomnia, and the major active ingredients are KGD and its metabolite KG8, which are distributed from the blood circulation into the brain by simple diffusion. KG8 is further metabolized into other metabolites that are easily excreted in the urine.

Dual Orexin Receptor Antagonist Attenuates Increases in IOP, ICP, and Translaminar Pressure Difference After Stimulation of the Hypothalamus in Rats.

PURPOSE: Intraocular pressure (IOP) remains the only modifiable risk factor for glaucoma progression. Our previous discovery that stimulation of nuclei within the hypothalamus can modulate IOP, intracranial pressure (ICP), and translaminar pressure difference (TLPD) fluctuations led us to investigate this pathway further. Our purpose was to determine the role of orexin neurons, primarily located in the dorsomedial hypothalamus (DMH) and perifornical (PeF) regions of the hypothalamus, in modulating these pressures. METHODS: Sprague Dawley rats were pretreated systemically with a dual orexin receptor antagonist (DORA-12) at 30 mg/Kg (n = 8), 10 mg/Kg (n = 8), or vehicle control (n = 8). The IOP, ICP, heart rate (HR), and mean arterial pressure (MAP) were recorded prior to and following excitation of the DMH/PeF using microinjection of the gamma-aminobutyric acid (GABA)A receptor antagonist bicuculline methiodide (BMI). RESULTS: Administration of the DORA at 30 mg/Kg significantly attenuated peak IOP by 5.2 ± 3.6 mm Hg (P = 0.007). During the peak response period (8-40 minutes), the area under the curve (AUC) for the 30 mg/Kg DORA cohort was significantly lower than the control cohort during the same period (P = 0.04). IOP responses for peak AUC versus DORA dose, from 0 to 30 mg/Kg, were linear (R2 = 0.18, P = 0.04). The ICP responses during the peak response period (4-16 minutes) versus DORA dose were also linear (R2 = 0.24, P = 0.014). Pretreatment with DORA significantly decreased AUC for the TLPD following stimulation of the DMH/PeF (10 mg/kg, P = 0.045 and 30 mg/kg, P = 0.015). CONCLUSIONS: DORAs have the potential to attenuate asynchronous changes in IOP and in ICP and to lessen the extent of TLPDs that may result from central nervous system (CNS) activation.

GABAB Receptor Antagonism from Birth to Weaning Permanently Modifies Kiss1 Expression in the Hypothalamus and Gonads in Mice.

INTRODUCTION: The kisspeptin gene Kiss1 is expressed in two hypothalamic areas: anteroventral periventricular nucleus/periventricular nucleus (AVPV/PeN) and arcuate nucleus (ARC), and also in gonads. Several pieces of evidence suggests that gamma-amino butyric acid B receptors (GABAB) signaling can regulate Kiss1 expression. Here, we inhibited GABAB signaling from PND2 to PND21 and evaluated the hypothalamic-pituitary-gonadal (HPG) axis. METHODS: BALB/c mice were treated on postnatal days 2-21 (PND2-PND21) with CGP55845 (GABAB antagonist) and evaluated in PND21 and adulthood: gene expression (qPCR) in the hypothalamus and gonads, hormones by radioimmunoassay, gonad histochemistry (H&E), puberty onset, and estrous cycles. RESULTS: At PND21, CGP inhibited Kiss1 and Tac2 and increased Pdyn and Gabbr1 in the ARC of both sexes and decreased Th only in female AVPV/PeN. Serum follicle-stimulating hormone (FSH) and testis weight were decreased in CGP-males, and puberty onset was delayed. In adults, Kiss1, Tac2, Pdyn, Pgr, Cyp19a1, and Gad1 were downregulated, while Gabbr1 was upregulated in the ARC of both sexes. In the AVPV/PeN, Kiss1, Th, Cyp19a1, and Pgr were decreased while Gad1 was increased in CGP-females, whereas Cyp19a1 was increased in CGP-males. Serum FSH was increased in CGP-males while prolactin was increased in CGP-females. Testosterone and progesterone were increased in ovaries from CGP-females, in which Kiss1, Cyp19a1, and Esr1 were downregulated while Hsd3b2 was upregulated, together with increased atretic and decreased ovulatory follicles. Testes from CGP-males showed decreased progesterone, increased Gabbr1, Kiss1, Kiss1r, and Esr2 and decreased Cyp19a1, and clear signs of seminiferous tubules atrophy. CONCLUSION: These results demonstrate that appropriate GABAB signaling during this critical prepubertal period is necessary for the normal development of the HPG axis.

Behavioural impairments after exposure of neonatal mice to propofol are accompanied by reductions in neuronal activity in cortical circuitry.

BACKGROUND: Both animal and retrospective human studies have linked extended and repeated general anaesthesia during early development with cognitive and behavioural deficits later in life. However, the neuronal circuit mechanisms underlying this anaesthesia-induced behavioural impairment are poorly understood. METHODS: Neonatal mice were administered one or three doses of propofol, a commonly used i.v. general anaesthetic, over Postnatal days 7-11. Control mice received Intralipid® vehicle injections. At 4 months of age, the mice were subjected to a series of behavioural tests, including motor learning. During the process of motor learning, calcium activity of pyramidal neurones and three classes of inhibitory interneurones in the primary motor cortex were examined in vivo using two-photon microscopy. RESULTS: Repeated, but not a single, exposure of neonatal mice to propofol i.p. caused motor learning impairment in adulthood, which was accompanied by a reduction of pyramidal neurone number and activity in the motor cortex. The activity of local inhibitory interneurone networks was also altered: somatostatin-expressing and parvalbumin-expressing interneurones were hypoactive, whereas vasoactive intestinal peptide-expressing interneurones were hyperactive when the mice were performing a motor learning task. Administration of low-dose pentylenetetrazol to attenuate γ-aminobutyric acid A receptor-mediated inhibition or CX546 to potentiate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-subtype glutamate receptor function during emergence from anaesthesia ameliorated neuronal dysfunction in the cortex and prevented long-term behavioural deficits. CONCLUSIONS: Repeated exposure of neonatal mice to propofol anaesthesia during early development causes cortical circuit dysfunction and behavioural impairments in later life. Potentiation of neuronal activity during recovery from anaesthesia reduces these adverse effects of early-life anaesthesia.

An increase in dendritic plateau potentials is associated with experience-dependent cortical map reorganization.

The organization of sensory maps in the cerebral cortex depends on experience, which drives homeostatic and long-term synaptic plasticity of cortico-cortical circuits. In the mouse primary somatosensory cortex (S1) afferents from the higher-order, posterior medial thalamic nucleus (POm) gate synaptic plasticity in layer (L) 2/3 pyramidal neurons via disinhibition and the production of dendritic plateau potentials. Here we address whether these thalamocortically mediated responses play a role in whisker map plasticity in S1. We find that trimming all but two whiskers causes a partial fusion of the representations of the two spared whiskers, concomitantly with an increase in the occurrence of POm-driven N-methyl-D-aspartate receptor-dependent plateau potentials. Blocking the plateau potentials restores the archetypical organization of the sensory map. Our results reveal a mechanism for experience-dependent cortical map plasticity in which higher-order thalamocortically mediated plateau potentials facilitate the fusion of normally segregated cortical representations.

The effect of GABAergic neurotransmission on the seizure-related activity of the laterodorsal thalamic nuclei and the somatosensory cortex in a genetic model of absence epilepsy.

The present study aimed to investigate the alterations of the GABAergic system in the laterodorsal nucleus (LDN) of the thalamus and the somatosensory cortex (SC) in an experimental model of absence seizure. The effects of pharmacological manipulation of both GABAA and GABAB receptor subunits in the LDN on the generation of spike-wave discharges (SWD) were evaluated. The experiments were carried out in four groups of both WAG/Rij and Wistar rats with 2 and 6 months of age. The expressions of various GABA receptor subunits were studied in the LDN and SC. Furthermore, recordings of unit activity from the LDN and electrocorticography were simultaneously monitored before, during, and after the application of GABAA and GABAB antagonists in the LDN. The generation of SWD in the older WAG/Rij rats was associated with significant alterations in the expression of GABAARα1, GABAARß3, and GABABR2 subunits in the LDN as well as GABAARα1, GABAARß3, GABAARγ2, and GABABR2 subunits in the SC. Furthermore, the occurrence of SWD was associated with a significant reduction of gene expression of GABAARα1 and increase of GABAARß3 in the LDN as well as reduction of GABAARα1, GABAARß3, GABAARγ2, and GABABR2 in the SC. The microionthophoretic application of the GABAA antagonist bicuculline resulted in a significant increase in the population firing rate of LDN neurons as well as the mean number and duration of SWD. The application of the GABAB antagonist CGP35348 significantly increased the population firing rate of LDN neurons but decreased the mean number of SWD. Our data indicate the regulatory effect of the GABAergic system of the LDN and SC in absence seizures.

Valproate selectively suppresses adolescent anabolic/androgenic steroid-induced aggressive behavior: implications for a role of hypothalamic γ-aminobutyric acid neural signaling.

Pubertal male Syrian hamsters (Mesocricetus auratus) treated with anabolic/androgenic steroids (AASs) during adolescence (P27-P56) display a highly intense aggressive phenotype that shares many behavioral similarities with pathological aggression in youth. Anticonvulsant drugs like valproate that enhance the activity of the γ-aminobutyric acid (GABA) neural system in the brain have recently gained acceptance as a primary treatment for pathological aggression. This study examined whether valproate would selectively suppress adolescent AAS-induced aggressive behavior and whether GABA neural signaling through GABAA subtype receptors in the latero-anterior hypothalamus (LAH; an area of convergence for developmental and neuroplastic changes that underlie aggression in hamsters) modulate the aggression-suppressing effect of this anticonvulsant medication. Valproate (1.0-10.0 mg/kg, intraperitoneal) selectively suppressed the aggressive phenotype in a dose-dependent fashion, with the effective anti-aggressive effects beginning at 5 mg/kg, intraperitoneally. Microinfusion of the GABAA receptor antagonist bicuculline (7.0-700 ng) into the LAH reversed valproate's suppression of AAS-induced aggression in a dose-dependent fashion. At the 70 ng dose of bicuculline, animals expressed the highly aggressive baseline phenotype normally observed in AAS-treated animals. These studies provide preclinical evidence that the anticonvulsant valproate selectively suppresses adolescent, AAS-induced aggression and that this suppression is modulated, in part, by GABA neural signaling within the LAH.

High-Dose Benzodiazepines Positively Modulate GABAA Receptors via a Flumazenil-Insensitive Mechanism.

Benzodiazepines (BZDs) produce versatile pharmacological actions through positive modulation of GABAA receptors (GABAARs). A previous study has demonstrated that high concentrations of diazepam potentiate GABA currents on the α1ß2γ2 and α1ß2 GABAARs in a flumazenil-insensitive manner. In this study, the high-concentration effects of BZDs and their sensitivity to flumazenil were determined on synaptic (α1ß2γ2, α2ß2γ2, α5ß2γ2) and extra-synaptic (α4ß2δ) GABAARs using the voltage-clamp electrophysiology technique. The in vivo evaluation of flumazenil-insensitive BZD effects was conducted in mice via the loss of righting reflex (LORR) test. Diazepam induced biphasic potentiation on the α1ß2γ2, α2ß2γ2 and α5ß2γ2 GABAARs, but did not affect the α4ß2δ receptor. In contrast to the nanomolar component of potentiation, the second potentiation elicited by micromolar diazepam was insensitive to flumazenil. Midazolam, clonazepam, and lorazepam at 200 µM exhibited similar flumazenil-insensitive effects on the α1ß2γ2, α2ß2γ2 and α5ß2γ2 receptors, whereas the potentiation induced by 200 µM zolpidem or triazolam was abolished by flumazenil. Both the GABAAR antagonist pentylenetetrazol and Fa173, a proposed transmembrane site antagonist, abolished the potentiation induced by 200 µM diazepam. Consistent with the in vitro results, flumazenil antagonized the zolpidem-induced LORR, but not that induced by diazepam or midazolam. Pentylenetetrazol and Fa173 antagonized the diazepam-induced LORR. These findings support the existence of non-classical BZD binding sites on certain GABAAR subtypes and indicate that the flumazenil-insensitive effects depend on the chemical structures of BZD ligands.

An Etiological Foxp2 Mutation Impairs Neuronal Gain in Layer VI Cortico-Thalamic Cells through Increased GABAB/GIRK Signaling.

A rare mutation affecting the Forkhead-box protein P2 (FOXP2) transcription factor causes a severe monogenic speech and language disorder. Mice carrying an identical point mutation to that observed in affected patients (Foxp2+/R552H mice) display motor deficits and impaired synaptic plasticity in the striatum. However, the consequences of the mutation on neuronal function, in particular in the cerebral cortex, remain little studied. Foxp2 is expressed in a subset of Layer VI cortical neurons. Here, we used Ntsr1-EGFP mice to identify Foxp2+ neurons in the mouse auditory cortex ex vivo. We studied the functional impact of the R552H mutation on the morphologic and functional properties of Layer VI cortical neurons from Ntsr1-EGFP; Foxp2+/R552H male and female mice. The complexity of apical, but not basal dendrites was significantly lower in Foxp2+/R552H cortico-thalamic neurons than in control Foxp2+/+ neurons. Excitatory synaptic inputs, but not inhibitory synaptic inputs, were decreased in Foxp2+/R552H mice. In response, homeostatic mechanisms would be expected to increase neuronal gain, i.e., the conversion of a synaptic input into a firing output. However, the intrinsic excitability of Foxp2+ cortical neurons was lower in Foxp2+/R552H neurons. A-type and delayed-rectifier (DR) potassium currents, two putative transcriptional targets of Foxp2, were not affected by the mutation. In contrast, GABAB/GIRK signaling, another presumed target of Foxp2, was increased in mutant neurons. Blocking GIRK channels strongly attenuated the difference in intrinsic excitability between wild-type (WT) and Foxp2+/R552H neurons. Our results reveal a novel role for Foxp2 in the control of neuronal input/output homeostasis.SIGNIFICANCE STATEMENT Mutations of the Forkhead-box protein 2 (FOXP2) gene in humans are the first known monogenic cause of a speech and language disorder. The Foxp2 mutation may directly affect neuronal development and function in neocortex, where Foxp2 is expressed. Brain imaging studies in patients with a heterozygous mutation in FOXP2 showed abnormalities in cortical language-related regions relative to the unaffected members of the same family. However, the role of Foxp2 in neocortical neurons is poorly understood. Using mice with a Foxp2 mutation equivalent to that found in patients, we studied functional modifications in auditory cortex neurons ex vivo We found that mutant neurons exhibit alterations of synaptic input and GABAB/GIRK signaling, reflecting a loss of neuronal homeostasis.

Astrocytes Control Sensory Acuity via Tonic Inhibition in the Thalamus.

Sensory discrimination is essential for survival. However, how sensory information is finely controlled in the brain is not well defined. Here, we show that astrocytes control tactile acuity via tonic inhibition in the thalamus. Mechanistically, diamine oxidase (DAO) and the subsequent aldehyde dehydrogenase 1a1 (Aldh1a1) convert putrescine into GABA, which is released via Best1. The GABA from astrocytes inhibits synaptically evoked firing at the lemniscal synapses to fine-tune the dynamic range of the stimulation-response relationship, the precision of spike timing, and tactile discrimination. Our findings reveal a novel role of astrocytes in the control of sensory acuity through tonic GABA release.

Acteoside Isolated from Colebrookea oppositifolia Smith Attenuates Epilepsy in Mice Via Modulation of Gamma-Aminobutyric Acid Pathways.

The present study was aimed to evaluate the anticonvulsant activity of acteoside and explore its mechanism of action. Initially, the acteoside was evaluated in maximal electroshock (MES) and pentylenetetrazole (PTZ)-induced convulsions, and later it was evaluated against N-methyl-D-aspartic acid (NMDA)-induced mortality in Swiss albino mice. Based on the response in these models, further evaluations were performed to explore the mechanism of action. In the results, the acteoside (10, 25, and 50 mg/kg) has shown significant anticonvulsant activity in the PTZ model (p < 0.01 for all doses); however, there was no protection observed in MES and NMDA models. Therefore, further mechanism-based studies were performed on the PTZ model, and the outcomes have revealed that there was a significant reduction in GABA (p < 0.01 for both regions) and elevation of glutamate (p < 0.01 for both regions) in the cortex and hippocampus regions of PTZ-treated animals. Further, the antioxidant levels (SOD, catalase, GPx, GR, GSH, LPO) were altered significantly (p < 0.01 for all parameters), with reduced GABAA mRNA levels (p < 0.01) in the PTZ control compared with the normal control. Interestingly, co-administration of acteoside (25 mg/kg) (p < 0.01 for all parameters) has restored all the PTZ-induced alterations compared to PTZ-control. Moreover, the anti-PTZ action of acteoside was completely blocked in the presence of flumazenil, and thus confirmed the GABAergic mechanism behind the anticonvulsant activity of acteoside. Besides, actophotometer and rotarod tests have confirmed that the acteoside is free from central side effects like motor incoordination and locomotor deficits.

Dynorphin and GABAA Receptor Signaling Contribute to Progesterone's Inhibition of the LH Surge in Female Mice.

Progesterone can block estrogen-induced luteinising hormone (LH) surge secretion and can be used clinically to prevent premature LH surges. The blocking effect of progesterone on the LH surge is mediated through its receptor in the anteroventral periventricular nucleus (AVPV) of the hypothalamus. However, the underlying mechanisms are unclear. The preovulatory LH surge induced by estrogen is preceded by a significant reduction in hypothalamic dynorphin and gamma-aminobutyric acid (GABA) release. To test the detailed roles of dynorphin and GABA in an LH surge blockade by progesterone, ovariectomized and 17ß-estradiol capsule-implanted (OVX/E2) mice received simultaneous injections of estradiol benzoate (EB) and progesterone (P) or vehicle for 2 consecutive days. The LH level was monitored from 2:30 pm to 8:30 pm at 30-minute intervals. Progesterone coadministration resulted in the LH surge blockade. A continuous microinfusion of the dynorphin receptor antagonist nor-BNI or GABAA receptor antagonist bicuculline into the AVPV from 3:00 pm to 7:00 pm reversed the progesterone-mediated blockade of the LH surge in 7 of 9 and 6 of 10 mice, respectively. In addition, these LH surges started much earlier than the surge induced by estrogen alone. However, 5 of 7 progesterone-treated mice did not show LH surge secretion after microinfusion with the GABAB receptor antagonist CGP-35348. Additionally, peripheral administration of kisspeptin-54 promotes LH surge-like release in progesterone treated mice. These results demonstrated that the progesterone-mediated suppression of the LH surge is mediated by an increase in dynorphin and GABAA receptor signaling acting though kisspeptin neurons in the AVPV of the hypothalamus in female mice.

Neurochemical effects of motor cortex stimulation in the periaqueductal gray during neuropathic pain.

OBJECTIVE: Motor cortex stimulation (MCS) is a neurosurgical technique used to treat patients with refractory neuropathic pain syndromes. MCS activates the periaqueductal gray (PAG) matter, which is one of the major centers of the descending pain inhibitory system. However, the neurochemical mechanisms in the PAG that underlie the analgesic effect of MCS have not yet been described. The main goal of this study was to investigate the neurochemical mechanisms involved in the analgesic effect induced by MCS in neuropathic pain. Specifically, we investigated the release of γ-aminobutyric acid (GABA), glycine, and glutamate in the PAG and performed pharmacological antagonism experiments to validate of our findings. METHODS: Male Wistar rats with surgically induced chronic constriction of the sciatic nerve, along with sham-operated rats and naive rats, were implanted with both unilateral transdural electrodes in the motor cortex and a microdialysis guide cannula in the PAG and subjected to MCS. The MCS was delivered in single 15-minute sessions. Neurotransmitter release was evaluated in the PAG before, during, and after MCS. Quantification of the neurotransmitters GABA, glycine, and glutamate was performed using a high-performance liquid chromatography system. The mechanical nociceptive threshold was evaluated initially, on the 14th day following the surgery, and during the MCS. In another group of neuropathic rats, once the analgesic effect after MCS was confirmed by the mechanical nociceptive test, rats were microinjected with saline or a glycine antagonist (strychnine), a GABA antagonist (bicuculline), or a combination of glycine and GABA antagonists (strychnine+bicuculline) and reevaluated for the mechanical nociceptive threshold during MCS. RESULTS: MCS reversed the hyperalgesia induced by peripheral neuropathy in the rats with chronic sciatic nerve constriction and induced a significant increase in the glycine and GABA levels in the PAG in comparison with the naive and sham-treated rats. The glutamate levels remained stable under all conditions. The antagonism of glycine, GABA, and the combination of glycine and GABA reversed the MCS-induced analgesia. CONCLUSIONS: These results suggest that the neurotransmitters glycine and GABA released in the PAG may be involved in the analgesia induced by cortical stimulation in animals with neuropathic pain. Further investigation of the mechanisms involved in MCS-induced analgesia may contribute to clinical improvements for the treatment of persistent neuropathic pain syndromes.

Tannins from Terminalia chebula fruits attenuates GABA antagonist-induced anxiety-like behaviour via modulation of neurotransmitters.

OBJECTIVES: This article investigates the anxiolytic activity of Terminalia chebula tannin-rich extract against picrotoxin (PTX; GABA antagonist)-induced anxiety in mice model. METHODS: Anxiolytic activity was studied by elevated plus maze (EPM), open field test (OFT), light/dark box test (LDT) and Vogel's conflict test (VCT). Electroencephalogram (EEG) was performed to know the changes in brain activity instigated by GABA antagonist. 5-hydroxytryptamine (5-HT), dopamine and norepinephrine levels in brain tissues were estimated by HPLC. The mRNA (CREB, BDNF, GABA, and 5-HT1A ) and protein expression (CREB, p-CREB, BDNF, ERK ½, p-ERK ½, GABAA Rα1, 5-HT1A and GAPDH) levels in brain tissue were determined by RT-PCR and Western blot analysis, respectively. KEY FINDINGS: Terminalia chebula tannin-rich extract (TCHE) supplementation increased locomotion in mice towards open arm (EPM), time spent in illuminated area (LDT), rearing frequency (OFT) and number of shocks (VCT) compared to PTX (P < 0.05). Furthermore, TCHE down-regulated serum cortisol levels and showed increased levels of 5-HT, DA and NE. Gene expressions such as BDNF, CREB, GABAA and 5-HT1A were up-regulated by TCHE treatment compared to PTX. CONCLUSIONS: Terminalia chebula tannin-rich extract showed significant anxiolytic activity against picrotoxin and could be used as natural therapy in neurodegenerative disorders.

Anxiolytic actions of Nardostachys jatamansi via GABA benzodiazepine channel complex mechanism and its biodistribution studies.

Nardostachys jatamansi has profound applications against pharmacological interventions and is categorized as a hypno-sedative drug according to Ayurveda. In the present study probable mechanism of anxiolytic action of Nardostachys jatamansi extract (NJE) was studied using behavioral anxiolytic tests (Elevated plus maze, Open field test, Light dark box test, and Vogel's conflict test) in mice. Mice were treated orally with NJE (250 mg/kg) for 3, 7 and 14 days or diazepam (1 mg/kg) followed by behavioral assessment and estimation of monoamine neurotransmitters, GABA, and antioxidant enzymes. Treatment of mice for 7 days caused an increase in time spent in open arms in elevated plus maze, number of line crossings in open field test, increased time spent in lit compartment of light-dark box test, an increase in number of licks made and shocks accepted in Vogel's conflict test, with results comparable to diazepam and this treatment also caused a significant increase in monoamine neurotransmitters and GABA in brain and tissue antioxidant parameters. Co-treatment of NJE with flumazenil (GABA-benzodiazepine antagonist; 0.5 mg/kg i.p) or picrotoxin (GABAA gated chloride channel blocker; 1 mg/kg i.p) caused a blockage/antagonised anxiolytic actions of NJE by causing a significant reduction in time spent in open arms of elevated plus maze, an decrease in number of line crossing in open field test and also number of shocks and licks accepted in Vogel's conflict test. Further, NJE was radiolabelled with technetium99m at their hydroxyl groups following which purity as well as in vivo and in vitro stability of radiolabelled formulations was evaluated. The blood kinetics and in vivo bio-distribution studies were carried out in rabbits and mice respectively. Labeled formulation was found to be stable in vitro (96 to 93% stability) and in vivo (96 to 92% stability). The labeled compound was cleared rapidly from blood (within 24 h) and accumulated majorly in kidneys (11.65 ± 1.33), liver (6.07 ± 0.94), and blood (4.03 ± 0.63) after 1 h. However, a small amount was observed in brain (0.1 ± 0.02) probably because of its inability to cross blood-brain barrier. These results highlight biodistribution pattern of NJE, and also indicated that a 7-day treatment with NJE produced significant anxiolytic effects in mice and also a significant increase in brain monoamine and GABA neurotransmitter levels and suggests that anxiolytic effects of NJE are primarily and plausibly mediated by activating GABAergic receptor complex.

Pharmacological manipulation of GABA activity in nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS) impairs figure-ground discrimination in pigeons: Running head: SP/IPS in figure-ground segregation.

Figure-ground segregation is a fundamental visual ability that allows an organism to separate an object from its background. Our earlier research has shown that nucleus rotundus (Rt), a thalamic nucleus processing visual information in pigeons, together with its inhibitory complex, nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS), are critically involved in figure-ground discrimination (Acerbo et al., 2012; Scully et al., 2014). Here, we further investigated the role of SP/IPS by conducting bilateral microinjections of GABAergic receptor antagonist and agonists (bicuculline and muscimol, respectively) and non-NMDA glutamate receptor antagonist (CNQX) after the pigeons mastered figure-ground discrimination task. We used two doses of each drug (bicuculline: 0.1 mM and 0.05 mM; muscimol: 4.4 mM and 8.8 mM; CNQX: 2.15 mM and 4.6 mM) in a within-subject design, and alternated drug injections with baseline (ACSF). The order of injections was randomized across birds to reduce potential carryover effects. We found that a low dose of bicuculline produced a decrement on figure trials but not on background trials, whereas a high dose impaired performance on background trials but not on figure trials. Muscimol produced an equivalent, dose-dependent impairment on both types of trials. Finally, CNQX had no consistent effect at either dose. Together, these results further confirm our earlier hypothesis that inhibitory projections from SP to Rt modulate figure-ground discrimination, and suggest that the Rt and the SP/IPS provide a plausible substrate that could perform figure-ground segregation in avian brain.

Acupuncture suppresses intravenous methamphetamine self-administration through GABA receptor's mediation.

OBJECTIVES: Methamphetamine is one of the widely abused drugs. In spite of a number of studies, there is still little successful therapy to suppress the methamphetamine abuse. Acupuncture has shown to attenuate the reinforcing effects of psychostimulant. Based on, the present study investigated if acupuncture could suppress intravenous methamphetamine self-administration behavior. In addition, a possible neuronal mechanism was investigated. MATERIALS & METHODS: Male Sprague-Dawley rats weighing 270-300g were trained to intake food pellet. After catheter implantation, animal was trained to self-administer methamphetamine (0.05mg/kg) intravenously using fixed ratio 1 schedule in daily 2h session during 3 weeks. After training, rats who established baseline (infusion variation less than 20% of the mean for 3 consecutive days) received acupuncture treatment on the next day. Acupuncture was performed at each acupoint manually. In the second experiment, the selective antagonists of GABAA or GABAB receptor were given before acupuncture to investigate the possible neuronal involvement of GABA receptor pathway in the acupuncture effects. C-Fos expression was examined in the nucleus accumbens to support behavioral data. RESULTS: Acupuncture at HT7, but not at control acupoint LI5, reduced the self-administration behavior significantly. Also, the effects of acupuncture were blocked by the GABA receptor antagonists. C-Fos expression was shown to be parallel with the behavioral data. CONCLUSIONS: Results of this study have shown that acupuncture at HT7 suppressed methamphetamine self-administration through GABA receptor system, suggesting that acupuncture at HT7 can be a useful therapy for the treatment of methamphetamine abuse.

Anticonvulsant effect of the hydroethanolic leaf extract of Psydrax subcordata (DC.) Bridson in murine models.

ETHNOPHARMACOLOGICAL RELEVANCE: Psydrax subcordata (DC.) Bridson is a tropical medicinal plant used traditionally for the management of epilepsy. However, there is little scientific evidence to support its use. AIM OF STUDY: The current study investigated the anticonvulsant properties of the hydroethanolic leaf extract of Psydrax subcordata (PSE) in animal models. MATERIALS AND METHODS: The anticonvulsant effects were evaluated in mouse models of acute seizures (pentylenetetrazole-, picrotoxin-, 4-aminopyridine-, strychnine- and maximal electroshock-induced seizure tests) and status epilepticus (Lithium/pilocarpine-induced SE). The role of GABAergic mechanisms in the actions of the extract was also examined by pre-treatment of animals with flumazenil in the pentylenetetrazole test. RESULTS: The extract (30, 100 and 300mg/kg, p.o.) significantly delayed the onset and decreased the duration and frequency of pentylenetetrazole- and picrotoxin-convulsions. PSE also reduced the duration of tonic hind limb extensions in the maximal electroshock-induced seizure test. Furthermore, PSE pre-treatment significantly delayed the onset of seizures and improved survival in the 4-aminopyridine-induced seizure test. In the strychnine-induced seizure test, PSE treatment did not significantly affect the latency to convulsions and time until death when compared to controls. PSE exhibited anticonvulsant effects in the lithium/pilocarpine test by delaying the onset of seizures and status epilepticus as well as reducing the severity of seizures and mortality of mice. Again, the anticonvulsant effect of PSE (100mg/kg, p.o.) was blocked by pre-treatment with flumazenil in the PTZ test. CONCLUSION: PSE has anticonvulsant activity in animal models, and this effect may be mediated, at least partly, through GABAergic mechanisms.

Inhibitory Modulation of Orbitofrontal Cortex on Medial Prefrontal Cortex-Amygdala Information Flow.

The amygdala receives cortical inputs from the medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC) that are believed to affect emotional control and cue-outcome contingencies, respectively. Although mPFC impact on the amygdala has been studied, how the OFC modulates mPFC-amygdala information flow, specifically the infralimbic (IL) division of mPFC, is largely unknown. In this study, combined in vivo extracellular single-unit recordings and pharmacological manipulations were used in anesthetized rats to examine how OFC modulates amygdala neurons responsive to mPFC activation. Compared with basal condition, pharmacological (N-Methyl-D-aspartate) or electrical activation of the OFC exerted an inhibitory modulation of the mPFC-amygdala pathway, which was reversed with intra-amygdala blockade of GABAergic receptors with combined GABAA and GABAB antagonists (bicuculline and saclofen). Moreover, potentiation of the OFC-related pathways resulted in a loss of OFC control over the mPFC-amygdala pathway. These results show that the OFC potently inhibits mPFC drive of the amygdala in a GABA-dependent manner; but with extended OFC pathway activation this modulation is lost. Our results provide a circuit-level basis for this interaction at the level of the amygdala, which would be critical in understanding the normal and pathophysiological control of emotion and contingency associations regulating behavior.

Regulation of sustained attention, false alarm responding and implementation of conditional rules by prefrontal GABAA transmission: comparison with NMDA transmission.

RATIONALE: Both prefrontal cortex (PFC) GABAA and NMDA transmission regulate attentional processes, yet how they may differentially regulate signal detection or other aspects of attention is unclear. OBJECTIVES: We examined PFC GABAA and NMDA receptor regulation of attention using a sustained attention task (SAT) permitting identification of distinct forms of impairments. As this task requires implementation of conditional rules, we also investigated how reducing PFC GABA transmission affected performance of visual and auditory conditional discriminations. METHODS: Male rats were well-trained on the SAT that required identifying whether a brief visual stimulus (500-50 ms) was present/absent by pressing one of two levers. They then received intra-PFC infusions of the GABAA antagonist bicuculline (12.5-50 ng), the NMDA antagonist MK-801 (6 µg), and i.p. injections of MK-801 (0.1-0.3 mg/kg) prior to testing. Separate groups were trained either on a similar task where the visual stimulus was presented for 2.5 s, or a task where presentation of one of two auditory cues required responding on a left or right lever. RESULTS: Both doses of bicuculline impaired vigilance, selectively increasing errors during nonsignal trials. Intra-PFC MK-801 induced subtle impairments at short signal durations. Systemic MK-801 impaired performance and increased response latencies. Visual and auditory conditional discrimination was impaired by 50 ng, but not 12.5 ng of bicuculline. CONCLUSIONS: These findings highlight a key role for PFC GABA transmission in reducing sensitivity to distractors during attentional performance. Furthermore, they reveal that disruption of GABA signaling can interfere with the ability to implement conditional rules.