Comparing impacts of the COVID-19 pandemic on training of public health Specialty Registrars starting before or after its onset.

Objectives: To capture and compare the differences in experiences of public health Specialty Registrars who commenced training prior to the COVID-19 pandemic (pre-pandemic Registrars) and those who commenced training during the pandemic (post-pandemic Registrars). Study design: This is a mixed methods study comprising a cross-sectional survey and participatory action research. Methods: A questionnaire of 10 open and 5 closed questions exploring participants experience of training during the pandemic was sent to East Midlands Specialty Registrars. Thematic analysis and double coding were undertaken, coded based on pre- or post-pandemic Registrar status. Participatory action research was then undertaken in 2 rounds with 2 groups, based on pre/post-pandemic status to consolidate themes. Results: The survey was completed by 17 Registrars (8 pre-pandemic, and 9 post-pandemic) and 19 Registrars took part in participatory action research. The findings showed pre-pandemic Registrars noted the importance of negative impacts on their mental health whilst post-pandemic Registrars were more positive and felt well supported in their training. Conclusions: There is a stark difference in the impact of the pandemic for Registrars who started training before compared to during the pandemic. The training programme was not resilient to the impact of the pandemic. Robustness could be increased by encouraging early leadership experience and providing wellbeing support, particularly for post pandemic Registrars now and in future.

Forage fish and polycyclic aromatic compounds in the Fort McMurray oil sands area: Body burden comparisons with environmental distributions and consumption guidelines.

The Fort McMurray region in northeastern Alberta (Canada) is rich in natural sources of polycyclic aromatic compounds (PACs) from exposed bitumen beds; anthropogenic sources are being released with increased oil sands industry expansion. Here we report on investigations of PACs (47 compounds) in three species of forage fish collected during the 2012-2013 Joint Oil Sands Monitoring Program (JOSMP) fish health investigations and compare results with PAC data for sediment and water collected under JOSMP and earlier programs. PAC concentrations in sediments varied three orders in magnitude and were highest at downstream tributary mouths, which flowed through the exposed McMurray Formation, and along reaches of the Athabasca River where the formation was exposed. PAC concentrations in water were less variable but with higher concentrations near exposed bitumen beds. Forage fish exhibited the weakest spatial gradients in ΣPACs concentration, which averaged 102 ±â€¯32 ng/g in trout-perch from the Athabasca River, 125 ±â€¯22 ng/g in lake chub from the Ells River, and 278 ±â€¯267 ng/g in slimy sculpin from the Steepbank, Firebag, and Dunkirk Rivers. Low-molecular weight compounds, particularly naphthalenes and fluorenes, dominated fish PACs. Phenanthrenes occurred in greater percent composition in fish caught in areas where PAC concentrations in sediments were higher due to the proximity of bitumen sources than in other areas. Dibenzothiophene, a major component of bitumen PAC, was a minor component of fish ΣPACs. Forage fish PAC concentrations were below fish consumption guidelines established by the European Commission (2011) and for the reopening of the commercial fisheries closed by the Deepwater Horizon oil spill. PAC concentrations in forage fish were similar to concentrations observed in many other studies (fish market surveys, estuaries, and marine waters) and lower than in fish sampled from highly impacted areas (near refineries, harbors, and other industrialized areas).

Development of a novel automated screening method for detection of FVIII Inhibitors.

INTRODUCTION: Factor VIII activity is routinely determined by measuring the activated partial thromboplastin time (aPTT) of a patient plasma sample and determining percent activity from a standard curve. To maximize the detection of a clotting factor inhibitor, a subjective assessment of parallelism of a patient curve compared with a standard curve is performed. We developed and validated an automated objective method to assess parallelism as a rapid screening tool for detection of an inhibitor to factor VIII during routine FVIII assays. METHODS: We performed FVIII assays on a subset of FVIII-deficient patients with hemophilia A with and without inhibitors. Utilizing a ratio of the slopes from parallelism curves obtained by an independent Microsoft excel program in patients compared with a normal standard curve, we determined a cutoff ratio predictive for presence of an inhibitor. RESULTS: A cutoff ratio of patient to control slopes of <0.45 for the detection of an inhibitor to FVIII was 100% sensitive and 91.6% specific, with a positive predictive value of 92.3% and a negative predictive value of 100%. CONCLUSION: Utilizing a ratio of the slopes from parallelism curves in patients with and without an inhibitor, we developed and validated a rapid, automated, and objective method to assess parallelism as an added screening tool for detection of an inhibitor to factor VIII during routine FVIII assays on a STAGO-based coagulation platform. This simple automated method has the potential to detect inhibitors to other clotting factors.

Comparative analysis of total mercury concentrations in anadromous and non-anadromous Arctic charr (Salvelinus alpinus) from eastern Canada.

Previous research has documented that total mercury concentrations ([THg]) are lower in anadromous Arctic charr than in non-anadromous conspecifics, but the two life-history forms have rarely been studied together. Here, data from nine pairs of closely-located anadromous and non-anadromous Arctic charr populations were used to explore the impact of biological and life-history factors on individual [THg] across a range of latitudes (49-81° N) in eastern Canada. Unadjusted mean [THg] ranged from 20 to 114 ng/g wet weight (ww) in anadromous populations, and was significantly higher in non-anadromous populations, ranging from 111 to 227 ng/g ww. Within-population variations in [THg] were best explained by fish age, and were often positively related to fork-length and δN-inferred trophic level. Differences in [THg] were not related to differences in length-at-age (i.e., average somatic growth rate) among populations of either life-history type. Mercury concentrations were not related to site latitude in either the anadromous or non-anadromous fish. We conclude that the difference in Arctic charr [THg] with life-history type could not be explained by differences in fish age, fork-length, trophic position, or length-at-age, and discuss possible factors contributing to low mercury concentrations in anadromous, relative to freshwater, fish.

Basal mercury concentrations and biomagnification rates in freshwater and marine food webs: effects on Arctic charr (Salvelinus alpinus) from eastern Canada.

Patterns of total Hg (THg) and methyl Hg (MeHg) biomagnification were investigated in six pairs of co-located lacustrine and marine food webs supporting a common predator, Arctic charr. Mercury biomagnification rates (the slope of log Hg concentration versus δ(15)N-inferred trophic level) did not differ significantly between the two feeding habitats for either THg or MeHg, but THg and MeHg concentrations at the base of the food web were higher in the lacustrine environment than in the marine environment. The proportion of THg as MeHg was related to trophic level, and the relationship was statistically similar in the lacustrine and marine habitats. The biomagnification rate of MeHg exceeded that of THg in both habitats. We conclude that the known difference in Hg concentration between anadromous and non-anadromous Arctic charr is driven by differential Hg concentrations at the base of the lacustrine and marine foodwebs, and not by differential biomagnification rates.

Spatial trends and historical deposition of mercury in eastern and northern Canada inferred from lake sediment cores.

Recent and historical deposition of mercury (Hg) was examined over a broad geographic area from southwestern Northwest Territories to Labrador and from the U.S. Northeast to northern Ellesmere Island using dated sediment cores from 50 lakes (18 in midlatitudes (41-50 degrees N), 14 subarctic (51-64 degrees N) and 18 in the Arctic (65-83 degrees N)). Distinct increases of Hg overtime were observed in 76% of Arctic, 86% of subarctic and 100% of midlatitude cores. Subsurface maxima in Hg depositional fluxes (microg m(-2) y(-1)) were observed in only 28% of midlatitude lakes and 18% of arctic lakes, indicating little recent reduction of inputs. Anthropogenic Hg fluxes adjusted for sediment focusing and changes in sedimentation rates (deltaF(adj,F)) ranged from -22.9 to 61 microg m(-2) y(-1) and were negatively correlated (r = -0.57, P < 0.001) with latitude. Hg flux ratios (FRs; post-1990)/pre-1850) ranged from 0.5 to 7.7. The latitudinal trend for Hg deltaF(adj,F) values showed excellent agreement with predictions of the global mercury model, GRAHM for the geographic location of each lake (r = 0.933, P < 0.001). The results are consistent with a scenario of slow atmospheric oxidation of mercury, and slow deposition of reactive mercury emissions, declining with increasing latitude away from emission sources in the midlatitudes, and support the view that there are significant anthropogenic Hg inputs in the Arctic.

PCB concentrations in lake trout (Salvelinus namaycush) are correlated to habitat use and lake characteristics.

This study considers the importance of lake trout habitat as a factor determining persistent organochlorine (OC) concentration. Lake trout is a stenothermal, cold water species and sensitive to hypoxia. Thus, factors such as lake depth, thermal stratification, and phosphorus enrichment may determine not only which lakes can support lake trout but may also influence among-lake variability in lake trout population characteristics including bioaccumulation of OCs. A survey of 23 lakes spanning much of the natural latitudinal distribution of lake trout provided a range of lake trout habitat to test the hypothesis that lake trout with greater access to littoral habitat for feeding will have lower concentrations of OCs than lake trout that are more restricted to pelagic habitat. Using the delta13C stable isotope signature in lake trout as an indicator of influence of benthic littoral feeding, we found a negative correlation between lipid-corrected delta13C and sigmaPCB concentrations supporting the hypothesis that increasing accessto littoral habitat results in lower OCs in lake trout. The prominence of mixotrophic phytoplankton in lakes with more contaminated lake trout indicated the pelagic microbial food web may exacerbate the biomagnification of OCs when lake trout are restricted to pelagic feeding. A model that predicted sigmaPCB in lake trout based on lake area and latitude (used as proximate variables for proportion of littoral versus pelagic habitat and accessibility to littoral habitat respectively) explained 73% of the variability in sigmaPCBs in lake trout in the 23 lakes surveyed.

Nefopam for the prevention of postoperative pain: quantitative systematic review.

Nefopam, a centrally acting analgesic, has been used in the surgical setting in many countries since the mid-1970s. However, clinical trials provide contflicting results for its analgesic potency. We performed a systematic search (multiple databases, bibliographies, any language, to January 2008) for randomized, placebo-controlled trials of nefopam for the prevention of postoperative pain. Data were combined using classic methods of meta-analyses and were expressed as weighted mean difference (WMD), relative risk (RR), and number needed to treat/harm (NNT/H) with 95% confidence interval (CI). Nine trials (847 adult patients, 359 received nefopam) were included. Nefopam (cumulative doses, 20-160 mg) was given orally or i.v., as single or multiple doses, or as a continuous infusion. Compared with placebo, cumulative 24 h morphine consumption was decreased with nefopam: WMD -13 mg (95% CI -17.9 to -8.15). Pain intensity at 24 h was also decreased: on a 100 mm visual analogue scale, WMD -11.5 mm (95% CI -15.1 to -7.85). The incidence of tachycardia was increased with nefopam (RR 3.12, 95% CI 1.11-8.79; NNH 7), as was the incidence of sweating (RR 4.92, 95% CI 2.0-12.1; NNH 13). There is limited evidence from the published literature that nefopam may be a useful non-opioid analgesic in surgical patients. The analgesic potency seems to be similar to non-steroidal anti-inflammatory drugs. However, dose responsiveness and adverse effect profile remain unclear, and the role of nefopam as part of multimodal analgesia needs to be established. Data in children are lacking.

Northern Rivers Ecosystem Initiative: distribution and effects of contaminants.

In response to a number of recommendations following the Northern Rivers Basin Studies (NRBS) contaminant program, the Northern Rivers Ecosystem Initiative (NREI) focused considerable attention on assessing contaminants from specific sources including pulp mill effluents, atmospheric transport of mercury and the Alberta oil sands operations. NRBS identified a number of major contaminants of concern including polychlorinated biphenyls, dioxins and furans, mercury and various hydrocarbons. Together, the NRBS and the NREI studies have demonstrated major declines in the levels of dioxins and furans over the last decade as pulp and paper mills have changed their process and treatment strategies in response to new Federal regulations. Polychlorinated biphenyls however, continue to be a concern for the region as their levels have not declined in fish and sediments over the course of these studies. Higher levels in sediments downstream of Grande Prairie and Hinton were identified, but the source of these contaminants remains unknown. Chlorinated pesticides were also investigated, and although toxaphene, DDT and other chlorinated organic pesticides were detected in fish tissue, they were present at very low levels. Studies on the oil sands industry in northern Alberta demonstrated limited impacts on the Athabasca River to date, although studies did identify slight to moderate impacts of natural oil seeps on fish and benthic communities in tributary streams. NREI studies also identified endocrine active compounds in the three pulp and paper mill effluents tested, but endocrine disruptive effects in wild fish were minimal. Municipal sewage effluents also contain endocrine active compounds and it is recommended that monitoring continue around these point sources.

Elevated mercury concentrations in fish in lakes in the Mackenzie River Basin: the role of physical, chemical, and biological factors.

During the mid-1990s and through the early 2000s, researchers determined that elevated mercury concentrations were a common occurrence in predatory fish in many lakes in the Mackenzie River Basin (MRB), located in northern Canada. Here we present the results of studies investigating factors contributing to higher mercury concentrations in fish in many of these lakes. Twenty-two percent of lake trout, 33% of northern pike, and 50% of walleye populations had mean mercury concentrations >0.5 microg/g, the guideline for the commercial sale of fish. Higher mercury concentrations were strongly associated with the relatively old age of MRB predatory fish; mean age ranged from 7.6 to 24.9 years for the three species. In contrast, none of the lake trout sampled in eight lakes further south in northern Saskatchewan and Alberta had mean mercury concentrations >0.5 microg/g; fish also were younger (mean age 6 years for the 8 lakes). Mercury concentrations in MRB fish generally increased with fish length, age, and trophic feeding although the nature of these relationships varied with the lake. Mean length was a good predictor of mean mercury concentrations in walleye populations across the study lakes but not for whitefish, lake trout, and pike; age was a good predictor for lake trout and walleye. Mercury concentrations in water and invertebrates were similar to those observed in more southerly regions where fish do not have elevated mercury concentrations. Mercury concentrations tended to be higher in fish in smaller vs. larger lakes and as a probable consequence of higher summer epilimnion temperatures, which favour a higher net methylation rate, and higher mercury and methyl mercury concentrations in water which enter these lakes from the watershed. Increasing fishing pressures on MRB lakes may be a means of reducing mean fish age, improving growth rates, and decreasing mercury body burdens. Increased global warming may result in higher mercury concentrations in fish through increased water temperatures, a longer ice free season, and increased release of stored mercury from the watershed into these lakes.

A history of total mercury in edible muscle of fish from lakes in northern Canada.

Subsistence fishing has been an important source of food for Native People in northern Canada since prehistoric time. Measurements of the levels of mercury in edible muscle of northern fish have been undertaken for over three decades in efforts to evaluate the risks of consuming northern fish. This report summarizes the data obtained from 7974 fish of 25 species from sites distributed from the Yukon to Labrador. The most abundant species were lake trout, lake whitefish, arctic char, walleye, northern pike and burbot. The question being asked was essentially "Are the fish safe to eat?" The results were used to support decisions on fishing and consumption of fish. They were sorted in several ways, into concentration ranges corresponding to human consumption guidelines, into political jurisdictions and into types of bedrock geology. Overall walleye, northern pike and lake trout, usually exceeded the subsistence consumption guideline of 0.2 microg g-1 total mercury and often exceeded the higher guideline of 0.5 microg g-1 total mercury for commercial sales of fish. Mercury in burbot, another facultative predator, was often lower but several still exceeding a guideline. Arctic char collections were mostly from anadromous populations and these had very low levels of mercury, presumably reflecting marine food sources. Lake whitefish were among the cleanest fish examined with 69 of 81 collections falling in the lowest range. Most collections were from sites in sedimentary rock. However a few sites were in metamorphic, intrusive or volcanic rocks and these, taken together, tended to have a higher proportion of sites in the higher ranges of mercury. These results indicate a widespread problem with mercury in subsistence fisheries for predator species of fish with the problem being most problematic for Nunavut.

Intraoperative human vagus nerve compound action potentials.

OBJECTIVE: Although electrical stimulation of vagus nerve is used widely for treatment of epilepsy the electrophysiological properties of human vagus nerve are not well characterized. Our objective was to measure compound action potentials of human vagus nerve fiber groups intraoperatively by stimulation using a commercially available generator and electrode system (Neurocybernetic Prosthesis System, NCP). MATERIAL AND METHODS: During NCP implantation we recorded compound action potentials evoked by stimulating the left vagus nerve through the NCP bipolar lead. Current intensities were varied from 0.25 to 3.0 mA. RESULTS: Vagus nerve compound action potential components conducting in the A, Adelta, and C velocity ranges could be elicited using either the NCP pulse generator or by a standard evoked potential instrument. A fiber potentials were recordable in all nerves, and were activated by very low stimulus currents. Adelta and C fibers were less reliably elicited, with C fibers requiring the highest currents. CONCLUSIONS: Three clearly identified fiber populations can be identified using therapeutic electrical stimulation of the human vagus. Intraoperative measurements of NCP-induced action potentials may potentially provide a marker for therapeutic stimulation and better insight into mechanisms of vagus nerve stimulation (VNS) efficacy.

Presynaptic muscarinic M(2)-receptor-mediated inhibition of N-type Ca(2+) channels in cultured sphenopalatine ganglion: direct evidence for acetylcholine inhibition of cerebral nitrergic neurogenic vasodilation.

Results of previous pharmacological studies suggested that presynaptic muscarinic M(2) receptors on cerebral perivascular nitric oxidergic (nitrergic) nerves mediated inhibition of nitric oxide release from these nerves. The inhibition was thought to be primarily attributable to a decreased Ca(2+) influx through N-type Ca(2+) channels on nitrergic nerves, but direct evidence supporting this hypothesis was not presented. In the present study, we used cultured rat sphenopalatine ganglion (SPG), a major source of nitrergic nerves to cerebral blood vessels, to investigate the role of muscarinic M(2) receptors in modulating voltage-dependent Ca(2+) channels. SPG neuronal soma and dendrites were immunoreactive for both N-type Ca(2+) channels and muscarinic M(2) receptors, indicating that muscarinic M(2) receptors were colocalized with N-type Ca(2+) channels. Using the whole-cell voltage-clamp technique, we found that voltage-dependent Ca(2+) currents in cultured SPG were largely blocked by omega-conotoxin, an N-type calcium channel antagonist, but were not affected by nifedipine, an L-type calcium antagonist. The Ca(2+) current was inhibited by acetylcholine (ACh) and arecaidine but-2-ynyl ester tosylate (ABET), a preferential muscarinic M(2)-receptor agonist, in a concentration-dependent manner. The inhibition was reversed by atropine and methoctramine (a muscarinic M(2)-receptor antagonist), but was not affected by muscarinic M(1)-, M(3)-, or M(4)-receptor antagonists. Consistent with this, preferential muscarinic M(1)-receptor agonists McN-A-343 and oxotremorine did not affect the Ca(2+) current. Furthermore, pretreatment with pertussis toxin and guanosine 5'-O-(3-thio)triphosphate prevented ACh and ABET inhibition of Ca(2+) currents. These results are consistent with pharmacological findings in the pig basilar arteries and provide direct evidence supporting our hypothesis that M(2)-receptor-mediated inhibition of cerebral nitrergic neurogenic vasodilation is due to a G(i)-protein-mediated suppression of Ca(2+) influx via voltage-dependent N-type Ca(2+) channels on perivascular nerves.

Age-related differences in NMDA responses in cultured rat hippocampal neurons.

The N-methyl-D-aspartate receptor (NMDAR) is expressed in the cerebral cortex and hippocampus and is important in learning and memory. NMDARs are influenced by aging and implicated in neurodegenerative disorders. We investigated age-related differences in NMDAR ionic currents and intracellular calcium in embryonic (E18), middle-age (9-10 month) and old (26 month) rat hippocampal neurons cultured in serum-free medium for 7-12 days. Responses to 200 microM NMDA with 50 microM glycine were measured using whole cell voltage clamp and fura-2 fluorescence. Embryonic neurons exhibited significantly larger and faster NMDA responses than adults. Old rats had 1.5 fold greater normalized NMDA peak current compared to middle-age rats, while intracellular calcium rose 1.3 fold higher. Differences in regression slopes generated from the integral of NMDA current versus normalized NMDA current indicate age-related differences are not exclusively due to changes in receptor density but likely influenced by changes in receptor function. Corresponding age-related measures of intracellular calcium by fura-2 fluorescence in response to NMDA showed a strong correlation with peak current (r(2)=0.996). Our data support the hypothesis that NMDAR responsiveness is altered during aging with an enhanced NMDA peak current in both old and embryonic neurons compared to middle-age neurons.

Temperature and time interval for culture of postmortem neurons from adult rat cortex.

For a model of neurological disease and ischemia, we extended recent work to culture adult postmortem rat brain neurons. Frontal cortex sections were removed from adult rats immediately following sacrifice and at different postmortem intervals and with the brain at either 22 degrees C or 4 degrees C. Brain could be stored four times longer at 4 degrees C between sacrifice and neuronal disaggregation to achieve the same 20% recovery of live cells from those plated compared to 22 degrees C. Each milligram of rat frontal cortex was estimated by the optical disector method to contain 160,000 neurons. When cells were isolated as rapidly as possible, 9% of the neurons originally present in the brain were viable. Various postmortem intervals from 2 to 24 hr resulted in a reduction from 6% to 3% of the cells originally present. After 5 days in culture, viable neurons were 23-42% of those isolated. Neuron-like cells that survived represented 40-75% of the viable cells, or 0.5-2.75% of those originally estimated to be present in the brain. Electrophysiology experiments show that cells isolated 0 and 24 hr postmortem had neuronal electrical properties, including an average resting membrane potential of -48 mV, voltage-sensitive currents, and action potentials. Neuron-like cells were immunoreactive for neuron-specific enolase, neurofilament 200, glutamate, MAP2, and tau after 2 weeks in culture. These experiments show that neuron-like cells can be reliably cultured from adult rat cortex up to 6 hr postmortem when stored at 22 degrees C and up to 24 hr postmortem when stored at 4 degrees C. These findings should encourage donation of human postmortem brain neurons for studies on ischemia, adult pharmacology, and neurological disease.

Cholinergic-nitrergic transmitter mechanisms in the cerebral circulation.

Cerebral blood vessels from several species are innervated by vasodilator nerves. Acetylcholine (ACh) released from parasympathetic cholinergic nerves was first suggested to be the transmitter for vasodilation. Results from pharmacological studies in isolated cerebral arterial ring preparations, however, have demonstrated that nitric oxide (NO) but not ACh mediates the major component of neurogenic vasodilation. More recently, ACh and NO have been shown to co-release from the same cholinergic-nitrergic nerves, and that ACh acts as a presynaptic transmitter in modulating NO release. In this communication, evidence for the neuronal origin of NO and possible role of ACh in modulating NO release in large cerebral arteries at the base of the brain will be discussed.

Inferior colliculus intracellular response abnormalities in vitro associated with susceptibility to ethanol withdrawal seizures.

During ethanol withdrawal (ETX), rats become susceptible to audiogenic seizures in which the inferior colliculus (IC) is known to play a critical role. The present study examined changes in membrane properties that occurred in IC dorsal cortex (ICd) neurons in brain slices from rats after 4 days of three times daily intragastric ethanol, which is proposed to be an analog of binge drinking. Compared with neurons from control animals, ICd neurons during ETX had action potentials (APs) with lower thresholds, a greater incidence of spontaneous APs, a reduced degree of spike firing adaptation, and an increased incidence of anode-break firing. With synaptic stimulation, epileptiform firing was seen in nearly 50% of ICd neurons during ETX but never was seen in normal ICd neurons except after perfusion of the gamma-aminobutyric acid type A (GABA(A)) antagonist bicuculline. Paired pulse responses of ICd neurons were also abnormal during ETX. Thus, in 75% of normal rats, paired synaptic stimuli inhibited the second response, but during ETX all neurons tested showed paired pulse facilitation. These aberrant membrane and synaptic properties provide direct evidence for the hyperexcitability of IC neurons during ETX. They may be due, in part, to changes in GABAergic and glutamatergic neurotransmission known to be produced during withdrawal after continued ethanol administration.

Decreased GABA and increased glutamate receptor-mediated activity on inferior colliculus neurons in vitro are associated with susceptibility to ethanol withdrawal seizures.

Cessation of ethanol administration in ethanol-dependent rats results in an ethanol withdrawal (ETX) syndrome, including audiogenic seizures (AGS). The inferior colliculus (IC) is the initiation site for AGS, and membrane properties of IC neurons exhibit hyperexcitability during ETX. Previous studies observed that ETX alters GABA and glutamate neurotransmission in certain brain sites. The present study evaluated synaptic properties and actions of GABA or glutamate antagonists during ETX in IC dorsal cortex (ICd) neurons in brain slices from rats treated with ethanol intragastrically 3 times daily for 4 days. A significant increase of spontaneous action potentials (APs) was observed during ETX. The width, area and rise time of excitatory postsynaptic potentials (EPSPs) evoked by stimulation in the commissure of IC were significantly elevated during ETX. A fast EPSP was sensitive to block by the non-NMDA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), and a slow EPSP was sensitive to the NMDA receptor antagonist, 2-amino-5-phosphonovalerate (AP5). However, during ETX the concentration of CNQX or AP5 needed to block these EPSPs was elevated significantly. Inhibitory postsynaptic potentials (IPSPs) in ICd neurons evoked in both normal and ETX rats were blocked by the GABA(A) antagonist, bicuculline. However, IPSPs during ETX displayed a significantly greater sensitivity to bicuculline. These data indicate that decreased GABA(A)-mediated inhibition and increased glutamate-mediated excitability in IC may both be critical mechanisms of AGS initiation during ETX, which is similar to observations in a genetic form of AGS. The common changes in IC neurotransmission in these AGS forms may be general mechanisms subserving AGS and other forms of auditory system pathophysiology in which the IC is implicated.