Milestone review: GABA, from chemistry, conformations, ionotropic receptors, modulators, epilepsy, flavonoids, and stress to neuro-nutraceuticals.

Arising out of a PhD project more than 50 years ago to synthesise analogues of the neurotransmitter GABA, a series of new chemical entities were found to have selective actions on ionotropic GABA receptors. Several of these neurochemicals are now commercially available. A new subtype of these receptors was discovered that could be a target for the treatment of myopia, the facilitation of learning and memory, and the improvement of post-stroke motor recovery. The development of these new chemical entities over many years demonstrates the importance of neurochemicals with which to investigate selective aspects of GABA receptors and illustrates the significance of collaboration between chemists and biologists in neurochemistry. Vital were the improvements in synthetic organic chemistry and the use of functional human receptors expressed in oocytes. Current interest in ionotropic GABA receptors includes the clinical development of subtype-specific agents and the role of gain-of-function receptor variants in epilepsy. Dietary flavonoids were found to cross the blood-brain barrier to influence brain function. Natural and synthetic flavonoids had a range of effects on GABA receptors, ranging from positive, silent, and negative allosteric modulators, to even second-order modulation of first-order modulators. Flavonoids have been called "a new family of benzodiazepines." Like benzodiazepines, flavonoids reduce stress. Stress produces changes in GABA receptors in the brain that may be because of changes in endogenous modulators, such as neurosteroids and corticosteroids. GABA also occurs naturally in the diet leading to studies of the effects of oral GABA on brain function. This finding has resulted in studies of GABA and related neurochemicals as neuro-nutraceuticals. GABA systems in the gut microbiome are essential to such studies. The actions of oral GABA and of GABA-enriched beverages and foodstuffs are now an area of considerable scientific and commercial interest. GABA is a deceptively simple chemical that can take up many shapes, which may underlie its complex functions. The need for new chemical entities with selective actions for further studies highlights the need for continuing collaboration between chemists and biologists.

A prospective observational cohort study comparing the treatment effectiveness and safety of ciclosporin, dupilumab and methotrexate in adult and paediatric patients with atopic dermatitis: results from the UK-Irish A-STAR register.

BACKGROUND: The main conventional systemic atopic dermatitis (AD) treatments are methotrexate (MTX) and ciclosporin (CyA). Dupilumab was the first novel systemic agent to enter routine clinical practice. There are no head-to-head randomised controlled trials or real-world studies comparing these agents directly. Network meta-analyses provide indirect comparative efficacy and safety data and have shown strong evidence for dupilumab and CyA. OBJECTIVES: The aim of this study was to compare the real-world clinical effectiveness and safety of CyA, dupilumab and MTX in AD. METHODS: We compared the effectiveness and safety of these systemic agents in a prospective observational cohort study of adult and paediatric patients recruited into the UK-Irish Atopic eczema Systemic TherApy Register (A-STAR). Treatment effectiveness measures included Eczema Area and Severity Index (EASI), Patient-Oriented Eczema Measure (POEM), Peak Pruritus Numerical Rating Scale (PP-NRS), Dermatology Life Quality Index (DLQI) and children's DLQI (cDLQI). Minimum duration of treatment was 28 days and follow-up was 12 months. Adjusted Cox-regression was used to compare the hazards of achieving EASI-50, EASI-75 and EASI-90 over time, and linear mixed-effects models were used to estimate changes in efficacy scores. Treatment safety was assessed by examining adverse events (AEs) at follow-up visits. RESULTS: 488 patients (n=311 adults and n=177 children/adolescents) on dupilumab (n=282), methotrexate (n=149), or CyA (n=57) were included. CyA and MTX were primarily used first line, while dupilumab was mainly a second line systemic as per UK National Institute of Clinical and Care Excellence (NICE) recommendations. EASI-50, EASI-75 and EASI-90 were achieved more rapidly in the dupilumab and CyA groups compared to MTX. After adjustment for previous severity, the reduction in EASI, POEM, PP-NRS and DLQI was greater for patients treated with dupilumab compared to MTX. In severe patients the reduction in EASI, POEM, and PP-NRS was even greater with CyA. The incidence of AEs was similar across groups (734, 654 and 594 per 10,000 person-month on CyA, dupilumab and MTX respectively). CONCLUSIONS: This real-world comparison of CyA, dupilumab and MTX in AD suggests that dupilumab is consistently more effective than MTX and that CyA is most effective in very severe disease within one follow-up year.

An expert consensus on managing dupilumab-related ocular surface disorders in people with atopic dermatitis 2024.

BACKGROUND: Atopic dermatitis (AD) is the most common inflammatory skin condition which affects all ages. New therapies, including the monoclonal antibody therapy dupilumab, offer excellent efficacy. However, in clinical trials, and emphasised in real-world observations, the unexpected increased frequency of ocular adverse effects became apparent. The effectiveness of dupilumab and the unpredictability of ocular adverse effects mean that clinicians need guidance on counselling patients prior to treatment and on managing them if they arise. OBJECTIVES: The British Association of Dermatologists (BAD) and Royal College of Ophthalmologists collaborated on this consensus guidance on managing dupilumab-related ocular surface disorders (DROSD). METHODS: A multidisciplinary group was formed of adult and paediatric dermatologists and ophthalmologists with DROSD expertise, patient representation, and BAD Clinical Standards Unit. A literature search was conducted, and the results reviewed. All recommendations were reviewed, discussed and voted on. RESULTS: The recommendations pertain to dermatology and ophthalmology management, and apply to all ages, unless otherwise stated. Importantly, initiation of dupilumab for AD should not be delayed for most eye disorders except acute new problems, e.g. infections, or potentially severe conditions, e.g. a history of corneal transplant (ophthalmology advice should be sought first). There is insufficient evidence to recommend lubricant drops prophylactically. Dermatologists should assess eye complaints to diagnose DROSD; a severity grading system is provided. DROSD management differs slightly in those aged <7 years as ocular complications may affect neuro-ocular development; therefore, irrespective of DROSD severity, this population should be referred for ophthalmology advice. In those aged ≥7 years, dermatologists should feel confident to trial treatment and reserve ophthalmology advice for severe or non-responding cases. Discussion about dupilumab withdrawal should be prompted by a significant impact on quality of life, threat to sight, or other complications. CONCLUSIONS: Although dupilumab is a highly effective agent for treating AD, the risk of ocular adverse effects should not inhibit clinicians or patients from using it, but clinicians should be aware of them. If a patient develops DROSD, there are clear pathways to assess severity and offer initial management; where ineffective, dermatologists should assess the urgency and seek advice from or initiate referral to ophthalmology. While the evidence reviewed for these guidelines reflects the extensive literature on dupilumab, we believe our advice has relevance for ocular surface disorders in atopic dermatitis (AD) patients treated with tralokinumab and lebrikizumab.

Sensitisation to the acrylate co-polymers glyceryl acrylate/acrylic acid co-polymer, sodium polyacrylate and acrylates/C10-30 alkyl acrylate cross-polymer (Carbopol®) is rare.

BACKGROUND: Acrylate polymers and cross-polymers (ACPs) are frequently used cosmetic ingredients. The British Society for Cutaneous Allergy (BSCA) and the UK Cosmetic, Toiletry and Perfumery Association (CTPA) collaborated to investigate the allergenic potential of three commonly-used ACPs. OBJECTIVES: The objective of this study is to determine the prevalence of allergic contact dermatitis (ACD) to three ACPs: glyceryl acrylate/acrylic acid co-polymer, sodium polyacrylate, and acrylates/C10-30 alkyl acrylate cross-polymer (Carbopol®). MATERIALS AND METHODS: The BSCA prospectively audited data collected from 20 centres in the UK and Ireland between 1st September 2021 and 1st September 2022. Patients with suspected ACD to (meth)acrylates, with facial dermatitis, or consecutive patients, were patch tested to glyceryl acrylate/acrylic acid co-polymer 10% aqueous (aq.) sodium polyacrylate 2% aq., and to acrylates/C10-30 alkyl acrylate cross-polymer 2% aq. (Carbopol®). The frequencies of positive, irritant, and doubtful reactions were recorded. RESULTS: In total, 1302 patients were patch tested. To glyceryl acrylate/acrylic acid co-polymer, there was one doubtful reaction in a patient allergic to multiple (meth)acrylates, and one irritant. To sodium polyacrylate, there were four irritant reactions, one doubtful, and one positive reaction; in all cases, relevance was unknown and there was no demonstrable (meth)acrylate allergy. There were no reactions to Carbopol®. CONCLUSIONS: Sensitisation to these concentrations of the three tested ACPs is rare. Elicitation of dermatitis in (meth)acrylate-sensitised patients by exposure to these three ACPs appears unlikely.

In memoriam: Frode Fonnum (1937-2023).

Frode Fonnum died unexpectedly on 26th April 2023, at 86 years of age. He was a tower of strength-a primeval force-in neuroscience, neurochemistry and toxicology. His highly cited publications, comprised salient evidence for GABA and glutamate as brain neurotransmitters. He served as an expert, and as an organizer, including of European research cooperation and as President of the International Society for Neurochemistry (ISN). Photo credit: Per Kristian Opstad.

Recommendation to update the British Society for Cutaneous Allergy corticosteroid series.

BACKGROUND: Patch testing is an important investigation when dermatitis is unresponsive to, or worsened by, topical corticosteroid treatment. There is a balance to be struck between testing too many allergens, which is expensive, time consuming and risks causing sensitization, and testing too few, which risks missing the diagnosis. The current British Society for Cutaneous Allergy (BSCA) corticosteroid series comprises eight allergens and was last updated in February 2007. AIM: To review and update the BSCA corticosteroid series. METHODS: We retrospectively analysed data from 16 patch test centres in the UK and Ireland for all patients who were patch tested to a corticosteroid series between August 2017 and July 2019. We recorded the allergens tested, the number and percentage tested to a corticosteroid series and the number of positive results for each allergen. We identified the allergens that test positive in ≥ 0.1% of selectively tested patients. RESULTS: Overall, 3531 patients were tested to a corticosteroid series in the 16 centres. The number of allergens tested ranged from 7 to 18 (mean 10). The proportion of patch test patients who were tested to a corticosteroid series ranged from 1% to 99%. Six allergens in the 2017 BSCA series tested positive in ≥ 0.1% of patients. Nine allergens not in the BSCA corticosteroid series tested positive in ≥ 0.1% of patients. CONCLUSION: This audit demonstrates the importance of regular review of recommended series and the significant variations in practice. The new BSCA corticosteroid series that we recommend contains 13 haptens, with the addition of the patient's own steroid creams as appropriate.

Ideal proportion of the population to be patch tested: How many should we be doing?

BACKGROUND: How many patients should we be patch testing? A previous study suggested that the minimum proportion of a population to be patch tested for allergic contact dermatitis was 1:700 annually. OBJECTIVES: To evaluate if the current minimum rate for patch testing has changed over the 20 years since the previous study in order to maximize the value. METHODS: In cooperation with the British Society for Cutaneous Allergy, a proforma for collation of retrospective data between January 2015 and December 2017 was sent to patch-test centers in the United Kingdom (UK) and the Republic of Ireland (ROI). The number of positive tests was analyzed against the proportion of population tested to see what proportion of the population would yield the greatest number of positive results. RESULTS: Responses from 11 centers showed that the minimum number needed to patch test had increased to 1:550 per head of population per year using the current criteria. CONCLUSIONS: In agreement with previous studies, we should be patch testing more people than we are. We could reduce the threshold for referral of patients we patch test to derive the most benefit from this investigation.

Formaldehyde 2% is not a useful means of detecting allergy to formaldehyde releasers- results of the ESSCA network, 2015-2018.

BACKGROUND: Studies suggest that patch testing with formaldehyde releasers (FRs) gives significant additional information to formaldehyde 1% aq. and should be considered for addition to the European baseline series (EBS). It is not known if this is also true for formaldehyde 2% aq. OBJECTIVES: To determine the frequency of sensitization to formaldehyde 2% aq. and co-reactivity with FRs. To establish whether there is justification for including FRs in the EBS. MATERIALS AND METHODS: A 4-year, multi-center retrospective analysis of patients with positive patch test reactions to formaldehyde 2% aq. and five FRs. RESULTS: A maximum of 15 067 patients were tested to formaldehyde 2% aq. and at least one FR. The percentage of isolated reactions to FR, without co-reactivity to, formaldehyde 2% aq. for each FR were: 46.8% for quarternium-15 1% pet.; 67.4% imidazolidinyl urea 2% pet.; 64% diazolidinyl urea 2% pet.; 83.3% 1,3-dimethylol-5, 5-dimethyl hydantoin (DMDM) hydantoin 2% pet. and 96.3% 2-bromo-2-nitropropane-1,3-diol 0.5% pet. This demonstrates that co-reactivity varies between FRs and formaldehyde, from being virtually non-existent in 2-bromo-2-nitropropane-1,3-diol 0.5% pet. (Cohen's kappa: 0, 95% confidence interval [CI] -0.02 to 0.02)], to only weak concordance for quaternium-15 [Cohen's kappa: 0.22, 95%CI 0.16 to 0.28)], where Cohen's kappa value of 1 would indicate full concordance. CONCLUSIONS: Formaldehyde 2% aq. is an inadequate screen for contact allergy to the formaldehyde releasers, which should be considered for inclusion in any series dependant on the frequency of reactions to and relevance of each individual allergen.

Patch test results with the European baseline series and additions thereof in the ESSCA network, 2015-2018.

BACKGROUND: Clinical surveillance of the prevalence of contact allergy in consecutively patch tested patients is a proven instrument to continually assess the importance of contact allergens (haptens) assembled in a baseline series. OBJECTIVES: To present current results from the European Surveillance System on Contact Allergies, including 13 countries represented by 1 to 11 departments. METHODS: Anonymized or pseudonymized patch test and clinical data from various data capture systems used locally or nationally as transferred to the Erlangen data centre were pooled and descriptively analysed after quality control. RESULTS: In the 4 years (2015-2018), data from 51 914 patients patch tested with the European baseline series (EBS) of contact allergens were analysed. Contact allergy to nickel was most frequent (17.6% positive), followed by contact allergy to fragrance mix I (6.9%), methylisothiazolinone (MI; 6.2%), and Myroxylon pereirae resin (balsam of Peru; 5.8%). CONCLUSIONS: While the prevalence of MI contact allergy decreased substantially following regulatory intervention, the persistently high levels of allergy to metals, fragrances, other preservatives, and rubber chemicals point to problems needing further research and, potentially, preventive efforts. Results with national additions to the baseline series provide important information on substances possibly to be considered for inclusion in the EBS.

The origins and early history of neurochemistry and its societies.

At the 2017 joint meeting of the International Society for Neurochemistry (ISN) and the European Society for Neurochemistry, 150 years of neurochemistry - the 50th anniversary of ISN, 40 years of European Society for Neurochemistry, and 60 years of the Journal of Neurochemistry (JNC) - was celebrated with a historical symposium that explored the foundations of neurochemical societies, key international figures in the discipline of neurochemistry, and the pre-eminent role of the JNC. The foundations of neurochemistry were laid in Europe, notably France and Germany, in the late 18th and early 19th centuries. Neurochemists in the United Kingdom made globally relevant contributions before and after the Second World War, and Swedish contributions were especially prominent in the 1950s and 1960s. As neurochemistry is a truly international branch of neuroscience, the important contributions of neurochemists in the Americas and the Asia-Pacific were also recognized, as were the seminal roles of the American, Asia-Pacific, and Japanese Societies of Neurochemistry. Although ISN was only formed in 1967, earlier international meetings in Europe and the Americas reflected the growing recognition of the importance of chemistry and biochemistry for understanding and responding to the pathophysiology of clinical conditions and diseases of the central and peripheral nervous systems. JNC was first published in 1956, but the ISN only assumed complete ownership of the journal under tempestuous circumstances in 1970. The ISN-JNC interface and the sterling work of the JNC Editors has meant that the income generated by the journal has allowed the ISN Council to implement diverse programs for supporting neurochemistry internationally, including sustaining regional neurochemical societies, and supporting neurochemists in the developing world and schools of neurochemistry.

A survey of members of the European Surveillance System on Contact Allergy and the EU project "StanDerm" to identify allergens tested in cosmetic series across Europe.

BACKGROUND: There is currently no agreed cosmetic series for use across Europe. OBJECTIVES: To establish allergens currently tested in local and national cosmetic series. METHOD: Members of the European Surveillance System on Contact Allergy and the European Cooperation in Science and Technology project TD1206 ("StanDerm") were surveyed to establish their current practice. RESULTS: A wide range of allergens was tested but there was significant variation between centres on the allergens considered to be important in screening for allergy to cosmetics. The number of allergens tested in addition to the baseline series varied between 2 and 50. CONCLUSIONS: There is a need for further investigation to establish the frequency and relevance of reactions to cosmetic allergens to enable an agreed evidence-based cosmetic series to be produced. Criteria for inclusion need to be established.

Optimising the transient expression of GABA(A) receptors in adherent HEK293 cells.

Owing to their therapeutic relevance, considerable efforts are devoted to the structural characterisation of membrane proteins. Such studies are limited by the availability of high quality protein due to the difficulty of overexpression in recombinant mammalian systems. We sought to systematically optimise multiple aspects in the process of transiently transfecting HEK293 cells, to allow the rapid expression of membrane proteins, without the lengthy process of stable clone formation. We assessed the impact of medium formulation, cell line, and harvest time on the expression of GABAA receptors, as determined by [3H]muscimol binding in cell membranes. Furthermore, transfection with the use of calcium phosphate/polyethyleneimine multishell nanoparticles was optimised, and a dual vector system utilising viral enhancing elements was designed and implemented. These efforts resulted in a 40-fold improvement in GABAA α1ß3 receptor expression, providing final yields of 22 fmol/cm2. The findings from this work provide a guide to the optimisation of transient expression of proteins in mammalian cells and should assist in the structural characterisation of membrane proteins.

Long-lasting effects of early-life intervention in mice on adulthood behaviour, GABAA receptor subunit expression and synaptic clustering.

Variations in the early postnatal environment of rodents produce long-term changes in responses to stress that may underlie neuropsychiatric diseases such as anxiety, depression and schizophrenia. GABAA receptors undergo marked changes in their subunit composition during this period, involving a regionally-dependent replacement of α2 with α1 subunits, the so-called α-subunit switch. In this study we examined the effects of early-life environment on adulthood GABAA receptor α1 and α2 subunit expression and the synaptic clustering of GABAA receptors. Male and female mice were exposed to either 15min daily handling sessions (EH) or no intervention (NH) over postnatal day (PND) 1-14. Adulthood behavioural differences in anxiety were assessed on the elevated plus-maze. Immunoperoxidase histochemistry was used to examine the density of the α1 and α2 subunit proteins. Double-labelling immunofluorescence and confocal microscopy were used to study GABAA receptor synaptic clustering. NH animals showed increased anxiety-type behaviours in the elevated plus maze relative to EH mice. NH males showed a loss of α2 subunits from the thalamus and lower layers of the somatosensory cortex, whilst NH females showed a reduction of α2 but increase in α1 protein in lower layers of the primary somatosensory cortex only. The NH condition also reduced α1 subunit expression in dentate gyrus (DG) in both males and females. Regardless of sex, NH mice showed reduced colocalisation of GABAA receptor α2 subunits with the synaptic marker gephyrin relative to the control condition. These findings suggest that early-life environment has long-lasting effects on GABAA receptors, leading to long-term changes in adulthood behaviour, and are of relevance to neurodevelopmental explanations of stress-augmented neuropsychiatric disorders.

European Surveillance System on Contact Allergies (ESSCA): polysensitization, 2009-2014.

BACKGROUND: Polysensitization, defined as being allergic to three or more haptens from the European baseline series, is considered to reflect increased susceptibility to developing a contact allergy, and is likely to be associated with an impaired quality of life. OBJECTIVES: To evaluate the prevalences of polysensitization across Europe and to analyse factors associated with polysensitization. METHODS: Patch test data collected by the European Surveillance System on Contact Allergies (ESSCA; www.essca-dc.org) in consecutively patch tested patients from January 2009 to December 2014, comprising 11 countries and 57 departments, were retrospectively analysed. RESULTS: A total of 86 416 patients were available for analysis, showing a standardized prevalence of polysensitization of 7.02%, ranging from 12.7% (Austria) to 4.6% (Italy). Allergen pairs with the strongest association are reported for the total population, for South Europe, and for North/Central Europe. Overall, polysensitized patients showed a higher percentage of extreme (+++) positive patch test reactions than oligosensitized patients. Female sex, occupational dermatitis and age > 40 years were risk factors for polysensitization. CONCLUSIONS: The varying prevalences of polysensitization across Europe most likely reflect differences in patient characteristics and referral patterns between departments. Known risk factors for polysensitization are confirmed in a European dermatitis population.

Some personal thoughts on the Australasian Society of Clinical and Experimental Pharmacologists in the 1980s.

There were a number of highly significant events regarding ASCEP in the 1980s: a tour of China by ASCEP pharmacologists; the Sydney IUPHAR Congress; and the initiation of the Australasian Visitor to the BPS scheme. ASCEP appointed a professional secretariat, established an investment portfolio, and initiated Special Interest Groups. The Society entered the 1990s welcoming toxicologists into the new ASCEPT.

GABA Australis, some reflections on the history of GABA receptor research in Australia.

Research on GABA receptors has a long history in Australia dating from 1958 with David Curtis and his colleagues in Canberra. This review traces many of the advances made in Australia guided by highly cited publications and some obscure ones. It covers the discovery of key chemicals with which to investigate GABA receptor function including bicuculline, muscimol, phaclofen, THIP and (+)-CAMP. Also described are findings relevant to the involvement of mutant GABA receptors in inherited epilepsy. The modulation of GABA receptors by a bewildering range of chemicals, especially by flavonoids and terpenoids, is discussed.

Unsaturated Analogues of the Neurotransmitter GABA: trans-4-Aminocrotonic, cis-4-Aminocrotonic and 4-Aminotetrolic Acids.

Analogues of the neurotransmitter GABA containing unsaturated bonds are restricted in the conformations they can attain. This review traces three such analogues from their synthesis to their use as neurochemicals. trans-4-Aminocrotonic acid was the first conformationally restricted analogue to be extensively studied. It acts like GABA across a range of macromolecules from receptors to transporters. It acts similarly to GABA on ionotropic receptors. cis-4-Aminocrotonic acid selectively activates bicuculline-insensitive GABAC receptors. 4-Aminotetrolic acid, containing a triple bond, activates bicuculline-sensitive GABAA receptors. These findings indicate that GABA activates GABAA receptors in extended conformations and GABAC receptors in folded conformations. These and related analogues are important for the molecular modelling of ionotropic GABA receptors and to the development of new agents acting selectively on these receptors.

Clinical outcomes and response of patients applying topical therapy for pyoderma gangrenosum: A prospective cohort study.

BACKGROUND: Pyoderma gangrenosum (PG) is an uncommon dermatosis with a limited evidence base for treatment. OBJECTIVE: We sought to estimate the effectiveness of topical therapies in the treatment of patients with PG. METHODS: This was a prospective cohort study of UK secondary care patients with a clinical diagnosis of PG that was suitable for topical treatment (recruited between July 2009 and June 2012). Participants received topical therapy after normal clinical practice (primarily topical corticosteroids [classes I-III] and tacrolimus 0.03% or 0.1%). The primary outcome was speed of healing at 6 weeks. Secondary outcomes included the following: proportion healed by 6 months; time to healing; global assessment; inflammation; pain; quality of life; treatment failure; and recurrence. RESULTS: Sixty-six patients (22-85 years of age) were enrolled. Clobetasol propionate 0.05% was the most commonly prescribed therapy. Overall, 28 of 66 (43.8%) ulcers healed by 6 months. The median time to healing was 145 days (95% confidence interval, 96 days to ∞). Initial ulcer size was a significant predictor of time to healing (hazard ratio, 0.94 [95% confidence interval, 0.88-1.00); P = .043). Four patients (15%) had a recurrence. LIMITATIONS: Our study did not include a randomized comparator. CONCLUSION: Topical therapy is potentially an effective first-line treatment for PG that avoids the possible side effects associated with systemic therapy. It remains unclear whether more severe disease will respond adequately to topical therapy alone.

Antidepressant, Anxiolytic and Antinociceptive Activities of Constituents from Rosmarinus Officinalis.

PURPOSE: Rosmarinus officinalis, traditionally known as rosemary, has been widely used in traditional medicines and has long been known as the herb of remembrance. However, few studies have investigated the effects of non-volatile components of rosemary on central nervous system function. METHODS: Fractionation of R. officinalis led to the isolation of salvigenin, rosmanol and cirsimaritin, which were investigated in mouse models of acute toxicity, antinociception (tail immersion and hot plate tests), depression (tail suspension and forced swim tests) and anxiety (elevated plus maze and light/dark box paradigms). RESULTS: Rosmanol, cirsimaritin and salvigenin were not found to exhibit any signs of acute toxicity (50-200 mg/kg), but elicited antinociceptive, antidepressant and anxiolytic activities. CONCLUSION: Rosmanol, cirsimaritin and salvigenin, all previously shown to have biphasic modulation of GABAA receptors, demonstrated CNS activity in mouse models of antinociception, antidepressant and anxiolysis. The anxiolytic activity of all three compounds was not ameliorated by flumazenil, but was inhibited by pentylenetetrazol, suggesting a mode of action via GABAA receptors at a site other than the high affinity benzodiazepine binding site. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Muscimol as an ionotropic GABA receptor agonist.

Muscimol, a psychoactive isoxazole from Amanita muscaria and related mushrooms, has proved to be a remarkably selective agonist at ionotropic receptors for the inhibitory neurotransmitter GABA. This historic overview highlights the discovery and development of muscimol and related compounds as a GABA agonist by Danish and Australian neurochemists. Muscimol is widely used as a ligand to probe GABA receptors and was the lead compound in the development of a range of GABAergic agents including nipecotic acid, tiagabine, 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol, (Gaboxadol(®)) and 4-PIOL.