Neonatal nicotine exposure impairs development of auditory temporal processing

Impacts of Perinatal Nicotine Exposure on nAChR Expression and Glutamatergic Synaptic Transmission in the Mouse Auditory Brainstem

Exposure to nicotine in utero, often due to maternal smoking, significantly elevates the risk of auditory processing deficits in offspring. This study investigated the effects of chronic nicotine exposure during a critical developmental period on the functional expression of nicotinic acetylcholine receptors (nAChRs), glutamatergic synaptic transmission, and auditory processing in the mouse auditory brainstem. We evaluated the functionality of nAChRs at a central synapse and explored the impact of perinatal nicotine exposure (PNE) on synaptic currents and auditory brainstem responses (ABR) in mice. Our findings revealed developmentally regulated changes in nAChR expression in the medial nucleus of the trapezoid body (MNTB) neurons and presynaptic Calyx of Held terminals. PNE was associated with enhanced acetylcholine-evoked postsynaptic currents and compromised glutamatergic neurotransmission, highlighting the critical role of nAChR activity in the early stages of auditory synaptic development. Additionally, PNE resulted in elevated ABR thresholds and diminished peak amplitudes, suggesting significant impairment in central auditory processing without cochlear dysfunction. This study provides novel insights into the synaptic disturbances that contribute to auditory deficits resulting from chronic prenatal nicotine exposure, underlining potential targets for therapeutic intervention.

Auditory brainstem responses are resistant to pharmacological modulation in Sprague Dawley wild-type and Neurexin1α knockout rats

Sensory processing in the auditory brainstem can be studied with auditory brainstem responses (ABRs) across species. There is, however, a limited understanding of ABRs as tools to assess the effect of pharmacological interventions. Therefore, we set out to understand how pharmacological agents that target key transmitter systems of the auditory brainstem circuitry affect ABRs in rats. Given previous studies, demonstrating that Nrxn1α KO Sprague Dawley rats show substantial auditory processing deficits and altered sensitivity to GABAergic modulators, we used both Nrxn1α KO and wild-type littermates in our study. First, we probed how different commonly used anesthetics (isoflurane, ketamine/xylazine, medetomidine) affect ABRs. In the next step, we assessed the effects of different pharmacological compounds (diazepam, gaboxadol, retigabine, nicotine, baclofen, and bitopertin) either under isoflurane or medetomidine anesthesia. We found that under our experimental conditions, ABRs are largely unaffected by diverse pharmacological modulation. Significant modulation was observed with (i) nicotine, affecting the late ABRs components at 90 dB stimulus intensity under isoflurane anesthesia in both genotypes and (ii) retigabine, showing a slight decrease in late ABRs deflections at 80 dB stimulus intensity, mainly in isoflurane anesthetized Nrxn1α KO rats. Our study suggests that ABRs in anesthetized rats are resistant to a wide range of pharmacological modulators, which has important implications for the applicability of ABRs to study auditory brainstem physiology.

Gender differences in the association between biomarkers of environmental smoke exposure and developmental disorders in children and adolescents

Effects of environmental tobacco smoke (ETS) exposure on children and adolescent health outcomes have been attracted more and more attention. In the present study, we seek to examine the gender-specific difference association of environmental smoke exposure biomarkers and developmental disorders in children and adolescents aged 6-15 years. US nationally representative sample collected from the National Health and Nutrition Examination Survey (NHANES) 2007-2014 was enrolled (N = 4428). Developmental disorders (DDs) are defined as a positive answer to the question, "Does your child receive special education or early intervention services?" Serum cotinine and urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) were utilized as acute and chronic exposure biomarkers of ETS, respectively. Participants with serum cotinine >0.015 ng/mL were considered as with acute ETS exposure, and participants with creatinine-adjusted NNAL >0.0006 ng/mL were considered as with chronic ETS exposure. A survey logistic regression model was used to estimate the association between ETS exposure biomarkers and DDs. Additive interaction was utilized to examine the interaction of gender and biomarkers of ETS. Overall, approximately 9% of children were defined as DDs, and 65% of children had serum cotinine and urinary NNAL levels above the limit of detection. In the adjusted models, the association of ETS exposure biomarkers with DDs was only observed in girls. Girls with low cotinine levels and high urinary NNAL levels had 2.074 (95% CI: 1.012-4.247) and 1.851 (95% CI: 1.049-3.265) times higher odds of being DDs than those without ETS exposure, respectively. However, the effects of boys and NNAL exposure on DDs have additively interacted. Our findings first provided strong evidence for gender differences in the association between two tobacco metabolites and DDs in children, disclosing the public health implications and economic burdens of environmental tobacco smoke exposure.

Low Intensity Noise Exposure Enhanced Auditory Loudness and Temporal Processing by Increasing Excitability of DCN

Sound stimulation is generally used for tinnitus and hyperacusis treatment. Recent studies found that long-term noise exposure can change synaptic and firing properties in the central auditory system, which will be detected by the acoustic startle reflex. However, the perceptual consequences of long-term low-intensity sound exposure are indistinct. This study will detect the effects of moderate-level noise exposure (83 dB SPL) on auditory loudness, and temporal processing was evaluated using CBA/CaJ mice. C-Fos staining was used to detect neural activity changes in the central auditory pathway. With two weeks of 83 dB SPL noise exposure (8 hours per day), no persistent threshold shift of the auditory brainstem response (ABR) was identified. On the other hand, noise exposure enhanced the acoustic startle response (ASR) and gap-induced prepulse inhibition significantly (gap-PPI). Low-level noise exposure, according to the findings, can alter temporal acuity. Noise exposure increased the number of c-Fos labeled neurons in the dorsal cochlear nucleus (DCN) and caudal pontine reticular nucleus (PnC) but not at a higher level in the central auditory nuclei. Our results suggested that noise stimulation can change acoustical temporal processing presumably by increasing the excitability of auditory brainstem neurons.

Behavioral and Gene Regulatory Responses to Developmental Drug Exposures in Zebrafish

Developmental consequences of prenatal drug exposure have been reported in many human cohorts and animal studies. The long-lasting impact on the offspring-including motor and cognitive impairments, cranial and cardiac anomalies and increased prevalence of ADHD-is a socioeconomic burden worldwide. Identifying the molecular changes leading to developmental consequences could help ameliorate the deficits and limit the impact. In this study, we have used zebrafish, a well-established behavioral and genetic model with conserved drug response and reward pathways, to identify changes in behavior and cellular pathways in response to developmental exposure to amphetamine, nicotine or oxycodone. In the presence of the drug, exposed animals showed altered behavior, consistent with effects seen in mammalian systems, including impaired locomotion and altered habituation to acoustic startle. Differences in responses seen following acute and chronic exposure suggest adaptation to the presence of the drug. Transcriptomic analysis of exposed larvae revealed differential expression of numerous genes and alterations in many pathways, including those related to cell death, immunity and circadian rhythm regulation. Differential expression of circadian rhythm genes did not correlate with behavioral changes in the larvae, however, two of the circadian genes, arntl2 and per2, were also differentially expressed at later stages of development, suggesting a long-lasting impact of developmental exposures on circadian gene expression. The immediate-early genes, egr1, egr4, fosab, and junbb, which are associated with synaptic plasticity, were downregulated by all three drugs and in situ hybridization showed that the expression for all four genes was reduced across all neuroanatomical regions, including brain regions implicated in reward processing, addiction and other psychiatric conditions. We anticipate that these early changes in gene expression in response to drug exposure are likely to contribute to the consequences of prenatal exposure and their discovery might pave the way to therapeutic intervention to ameliorate the long-lasting deficits.

Melatonin protects cochlear hair cells from nicotine-induced injury through inhibiting apoptosis, inflammation, oxidative stress and endoplasmic reticulum stress

Hearing loss positively links with cigarette smoking. However, the involved mechanism and treatment strategies are largely unrevealed. This study aimed to investigate the damaging effect of nicotine on cochlear hair cells, reveal the underlying mechanism and evaluate the therapeutic effect of melatonin on nicotine-induced injury. The results showed that nicotine induced cytotoxicity of House Ear Institute-Organ of Corti 1 (HEI-OC1) cochlear hair cells in a dose-dependent manner (0, 2.5, 5, 10, 20, 40 and 80 μM). Functional investigations showed that nicotine (10 μM) stimulation dramatically promoted apoptosis, inflammatory response, oxidative stress and endoplasmic reticulum stress in HEI-OC1 cells. Moreover, melatonin treatment dose-dependently alleviated the nicotine-induced cytotoxicity in HEI-OC1 cells (0, 10 25, 50 and 100 μM). Further investigation showed that melatonin (100 μM) effectively attenuated the nicotine-induced apoptosis, inflammation, oxidative stress and endoplasmic reticulum stress in HEI-OC1 cells. Collectively, we demonstrated that nicotine induced apoptosis, inflammation, oxidative stress and endoplasmic reticulum stress of cochlear hair cells in an in vitro cell model. Melatonin showed protective effect on these aspects, suggesting that melatonin may be a potential agent for treating smoking-induced hearing loss.

Impact of Nicotine Exposure on Hair Cell Toxicity and Embryotoxicity During Zebrafish Development

Objectives

Nicotine has various adverse effects including negative impacts associated with maternal exposure. In the current study, we examined nicotine-induced damage of hair cells and embryotoxicity during zebrafish development.

Methods

Zebrafish embryos were exposed to nicotine at several concentrations (5, 10, 20, and 40 μM) and embryotoxicity were evaluated at 72 hours, including hatching rate, mortality, teratogenicity rate, and heart rate. Hair cells within the supraorbital (SO1 and SO2), otic (O1), and occipital (OC1) neuromasts were identified at 120 hours. Apoptosis and mitochondrial damage of hair cells were analyzed using TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling) and DASPEI (2-[4-(dimethylamino)styryl]-N-ethylpyridinium iodide) assays, respectively, and changes of ultrastructure were observed by scanning electron microscopy.

Results

The control group without nicotine appeared normal with overall mortality and teratogenicity rate <5%. The hatching rate and mortality rate was not significantly different according to nicotine concentration (n=400 each). The abnormal morphology rate (n=400) increased and heart rate (n=150) decreased with increasing nicotine concentration (P<0.05). Nicotine-induced hair cell damage significantly increased as nicotine concentration increased. A significantly greater number of TUNEL-positive cells (P<0.01) and markedly smaller DASPEI area (P<0.01) were shown as nicotine concentration increased.

Conclusion

The current results suggest that nicotine induces dose-dependent hair cell toxicity in embryos by promoting apoptosis and mitochondrial and structural damage.

Effects of transient auditory deprivation during critical periods on the development of auditory temporal processing

OBJECTIVES

The central auditory pathway matures through sensory experiences and it is known that sensory experiences during periods called critical periods exert an important influence on brain development. The present study aimed to investigate whether temporary auditory deprivation during critical periods (CPs) could have a detrimental effect on the development of auditory temporal processing.

MATERIALS AND METHODS

Twelve neonatal rats were randomly assigned to control and study groups; Study group experienced temporary (18-20 days) auditory deprivation during CPs (Early deprivation study group). Outcome measures included changes in auditory brainstem response (ABR), gap prepulse inhibition of the acoustic startle reflex (GPIAS), and gap detection threshold (GDT). To further delineate the specific role of CPs in the outcome measures above, the same paradigm was applied in adult rats (Late deprivation group) and the findings were compared with those of the neonatal rats.

RESULTS

Soon after the restoration of hearing, early deprivation study animals showed a significantly lower GPIAS at intermediate gap durations and a larger GDT than early deprivation controls, but these differences became insignificant after subsequent auditory inputs. Additionally, the ABR results showed significantly delayed latencies of waves IV, V, and interpeak latencies of wave I-III and wave I-V in study group. Late deprivation group didn't exhibit any deterioration in temporal processing following sensory deprivation.

CONCLUSION

Taken together, the present results suggest that transient auditory deprivation during CPs might cause reversible disruptions in the development of temporal processing.

The effects of postnatal phthalate exposure on the development of auditory temporal processing in rats

OBJECTIVE

The central auditory pathway is known to continue its development during the postnatal critical periods and is shaped by experience and sensory inputs. Phthalate, a known neurotoxic material, has been reported to be associated with attention deficits in children, impacting many infant neurobehaviors. The objective of this study was to investigate the potential effects of neonatal phthalate exposure on the development of auditory temporal processing.

METHODS

Neonatal Sprague-Dawley rats were randomly assigned into two groups: The phthalate group (n = 6), and the control group (n = 6). Phthalate was given once per day from postnatal day 8 (P8) to P28. Upon completion, at P28, the Auditory Brainstem Response (ABR) and Gap Prepulse Inhibition of Acoustic Startle response (GPIAS) at each gap duration (2, 5, 10, 20, 50 and 80 ms) were measured, and gap detection threshold (GDT) was calculated. These outcomes were compared between the two groups.

RESULTS

Hearing thresholds by ABR showed no significant differences at all frequencies between the two groups. Regarding GPIAS, no significant difference was observed, except at a gap duration of 20 ms (p = 0.037). The mean GDT of the phthalate group (44.0 ms) was higher than that of the control group (20.0 ms), but without statistical significance (p = 0.065). Moreover, the phthalate group tended to demonstrate more of a scattered distribution in the GDT group than the in the control group.

CONCLUSION

Neonatal phthalate exposure may disrupt the development of auditory temporal processing in rats.

Effect of passive smoking on auditory temporal resolution in children

OBJECTIVE

To determine the effect of passive smoking on auditory temporal resolution in primary school children, based on the hypothesis that individuals who are exposed to smoking exhibit impaired performance.

DESIGN

Auditory temporal resolution was evaluated using the Gaps In Noise (GIN) test. Exposure to passive smoking was assessed by measuring nicotine metabolite (cotinine) excreted in the first urine of the day.

STUDY SAMPLE

The study included 90 children with mean age of 10.2 ± 0.1 years old from a public school in São Paulo. Participants were divided into two groups: a study group, comprising 45 children exposed to passive smoking (cotinine > 5 ng/mL); and a control group, constituting 45 children who were not exposed to passive smoking. All participants had normal audiometry and immittance test results.

RESULTS

Statistically significant differences (p < 0.005) in performance on the GIN test were found between the two groups, with mean thresholds of 5.3 ms and 68.9% correct responses in the study group versus 4.6 ms and 74.0% in the control group.

CONCLUSION

The children exposed to passive smoking had poorer performance both in terms of thresholds and correct responses percentage on auditory temporal resolution assessment.

Perinatal nicotine exposure impairs the maturation of glutamatergic inputs in the auditory brainstem

KEY POINTS

Chronic perinatal nicotine exposure causes abnormal auditory brainstem responses and auditory processing deficits in children and animal models. The effect of perinatal nicotine exposure on synaptic maturation in the auditory brainstem was investigated in granule cells in the ventral nucleus of the lateral lemniscus, which receive a single calyx-like input from the cochlear nucleus. Perinatal nicotine exposure caused a massive reduction in the amplitude of the excitatory input current. This caused a profound decrease in the number and temporal precision of spikes in these neurons. Perinatal nicotine exposure delayed the developmental downregulation of functional nicotinic acetylcholine receptors on these neurons.

ABSTRACT

Maternal smoking causes chronic nicotine exposure during early development and results in auditory processing deficits including delayed speech development and learning difficulties. Using a mouse model of chronic, perinatal nicotine exposure we explored to what extent synaptic inputs to granule cells in the ventral nucleus of the lateral lemniscus are affected by developmental nicotine treatment. These neurons receive one large calyx-like input from octopus cells in the cochlear nucleus and play a role in sound pattern analysis, including speech sounds. In addition, they exhibit high levels of α7 nicotinic acetylcholine receptors, especially during early development. Our whole-cell patch-clamp experiments show that perinatal nicotine exposure causes a profound reduction in synaptic input amplitude. In contrast, the number of inputs innervating each neuron and synaptic release properties of this calyx-like synapse remained unaltered. Spike number and spiking precision in response to synaptic stimulation were greatly diminished, especially for later stimuli during a stimulus train. Moreover, chronic nicotine exposure delayed the developmental downregulation of functional nicotinic acetylcholine receptors on these neurons, indicating a direct action of nicotine in this brain area. This presumably direct effect of perinatal nicotine exposure on synaptic maturation in the auditory brainstem might be one of the underlying causes for auditory processing difficulties in children of heavy smoking mothers.

Developmental Trajectories of Auditory Cortex Synaptic Structures and Gap-Prepulse Inhibition of Acoustic Startle Between Early Adolescence and Young Adulthood in Mice

Cortical excitatory and inhibitory synapses are disrupted in schizophrenia, the symptoms of which often emerge during adolescence, when cortical excitatory synapses undergo pruning. In auditory cortex, a brain region implicated in schizophrenia, little is known about the development of excitatory and inhibitory synapses between early adolescence and young adulthood, and how these changes impact auditory cortex function. We used immunohistochemistry and quantitative fluorescence microscopy to quantify dendritic spines and GAD65-expressing inhibitory boutons in auditory cortex of early adolescent, late adolescent, and young adult mice. Numbers of spines decreased between early adolescence and young adulthood, during which time responses increased in an auditory cortex-dependent sensory task, silent gap-prepulse inhibition of the acoustic startle reflex (gap-PPI). Within-bouton GAD65 protein and GAD65-expressing bouton numbers decreased between late adolescence and young adulthood, a delay in onset relative to spine and gap-PPI changes. In mice lacking the spine protein kalirin, there were no significant changes in spine number, within-bouton GAD65 protein, or gap-PPI between adolescence and young adulthood. These results illustrate developmental changes in auditory cortex spines, inhibitory boutons, and auditory cortex function between adolescence and young adulthood, and provide insights into how disrupted adolescent neurodevelopment could contribute to auditory cortex synapse pathology and auditory impairments.

Dose passive smoking induce sensorineural hearing loss in children?

OBJECTIVES

Smoking plays major role in development of vascular and respiratory serious diseases. It has been reported that negative smoker children are prone for conductive hearing impairment due to repeated attacks of Eustachian tube dysfunction and middle ear effusion. This study aims to identify negative smoking as potential risk factor for development of sensorineural hearing loss.

STUDY

This study was done between January 2010 and November 2012. 411 children aged 5-11 years (8.2 ± 1.5) participated in this study; they were children attending the Ear, Nose, and Throat clinic of a tertiary care hospital and their siblings. The inclusion criteria were: (i) normal speech and language, (ii) absence of any disease or condition that may cause sensorineural hearing loss, and (iii) normal middle ear function on the day of hearing assessment. They were divided into three groups according to the exposure to second-hand smoke at home; group of "no exposure" whereas no smoker in the family (131 children), group of 'mild exposure" whereas the father was the only smoking parent and smoking was prohibited at home (155 children), and group of "heavy exposure", whereas the mother was smoking, or the father was freely smoking at home and in the presence of his children (125 children). Audiological evaluation in the form of pure tone and speech audiometry and immitancemetry was done for the study group.

RESULTS

Audiological evaluation revealed that the prevalence of hearing loss was 3.8%, 4.5% and 12% in the "no exposure", "mild exposure", and "heavy exposure" groups, respectively. Significant difference was only detected between the high exposure group and the other two groups. All children had minimal sensorineural hearing loss, i.e. threshold of frequencies showing hearing loss was 20 or 25 dB HL. The risk ratios (95% confidence interval) for hearing loss in the study subgroups were 1.18 (0.38, 3.64) for mild exposure group (p>0.05), 3.14 (1.18, 8.3) for heavy exposure group (p<0.05).

CONCLUSIONS

Passive smoking in childhood correlates with sensorineural hearing loss, and it is an important risk factor for development of minimal hearing loss. Strict prevention of children exposure to second-hand smoke should be encouraged by every mean.

Tobacco smoke exposure during childhood: effect on cochlear physiology

The rate of smoking in Brazil is about 18.8%. Exposure to environmental tobacco smoke is one of the major factors predisposing children to several hazardous health problems. The objective of the present research was to analyze the effect of tobacco smoke exposure during childhood on cochlear physiology by measuring the transient evoked otoacoustic emissions (TEOAE) response levels. Cotinine, the main metabolite of nicotine, was measured in 145 students’ (8–10 years old) urine. Sixty students indicated tobacco smoke exposure (TSE) (cotinine urine levels ≥ 5.0 ng/mL) and 85 did not. The evaluation of TEOAE of TSE students showed lower response levels, mainly on frequencies of 2.8 kHz on the right and left ears and 2.0 kHz on left ear and lower signal noise response levels, mainly on the 1.0 kHz and 1.4 kHz frequencies, when compared to controls that were not exposed to tobacco. The mean hearing loss in tobacco smoke exposure children was 2.1 dB SPL. These results have important implications on the damage to the cochlear structures and indicate a possible loss in hearing and hearing ability development.

Effects of intravenous nicotine on prepulse inhibition in smokers and non-smokers: relationship with familial smoking

RATIONALE

The reinforcing properties of nicotine may be, in part, derived from its ability to enhance certain forms of cognitive processing. Several animal and human studies have shown that nicotine increases prepulse inhibition (PPI) of the startle reflex. However, it remains unclear whether these effects are related to smoking susceptibility.

OBJECTIVES

The current study examined the effects of intravenously delivered nicotine on PPI in smokers and non-smokers, as well as its association with a quantitative index of familial smoking.

METHODS

The sample consisted of 30 non-smokers and 16 smokers, who completed an initial assessment, followed on a separate day by a laboratory assessment of PPI prior to and following each of two intravenous nicotine infusions. Separate doses were used in smoker and non-smoker samples.

RESULTS

Analyses indicated that both nicotine infusions acutely enhanced PPI among non-smokers, and this enhancement was positively related to the degree of smoking among first and second-degree relatives. Smokers also displayed PPI enhancement after receiving the first infusion, but this effect was unrelated to familial smoking.

CONCLUSIONS

These data suggest that the PPI paradigm may have utility as an endophenotype for cognitive processes which contribute to smoking risk.

Environmental noise affects auditory temporal processing development and NMDA-2B receptor expression in auditory cortex

Auditory temporal processing is essential for sound discrimination and speech comprehension. Under normal developmental conditions, temporal processing acuity improves with age. As recent animal studies have shown that the functional development of the auditory cortex (AC) is impaired by early life exposure to environmental noise (i.e., continuous, moderate-level, white noise), here we investigated whether the normal age-related improvement in temporal processing acuity is sensitive to delayed development of the AC. We used a behavioral paradigm, the gap-induced prepulse inhibition of the acoustic startle reflex, to assess the gap detection threshold, and provide a comparison of temporal processing acuity between environmental noise-reared rats and age-matched controls. Moreover, because age-related changes normally occur in the relative expression of different N-methyl-D-aspartate (NMDA) receptor subunits, we assessed the level of protein expression of NMDA-2A and 2B receptors (NR2A and NR2B respectively) in the AC after environmental noise-rearing. As hypothesized, rats reared in environmental noise showed (1) poor temporal processing acuity as adults (i.e., gap detection threshold remained elevated at a juvenile-like level), and (2) an increased level of NR2B protein expression compared to age-matched controls. This poor temporal processing acuity represented delayed development rather than permanent impairment, as moving these environmental noise-reared rats to normal acoustic conditions improved their gap detection threshold to an age-appropriate level. Furthermore, housing normally reared, adult rats in environmental noise for two months did not affect their already-mature gap detection threshold. Thus, masking normal sound inputs with environmental noise during early life, but not adulthood, impairs temporal processing acuity as assessed with the gap detection threshold.

Vascular and morphogenetic abnormalities associated with exposure of cigarette smoke condensate during chicken and murine embryogenesis

OBJECTIVE

Embryonic movements (EM) and angiogenesis pathways are evolutionarily conserved mechanisms which are essential for proper embryonic development. Deviations in these processes by exposure to cigarette smoke condensate (CSC) may cause vascular and morphogenetic disorders.

METHODS

Using chicken and mouse embryos, we have demonstrated the in vivo effects of CSC on EM, vascular development, and organogenesis.

RESULTS

Examination of the CSC exposed chicken embryos revealed a significant reduction in EM, stunted growth, deviated pattern of blood vessels, hemorrhages, and localized necrosis. Likewise, mouse embryos that were exposed to CSC at E8.5 and E9.5 died between E11.5 and E12.5, respectively. These mouse embryos showed defects in morphogenesis and remodeling of the embryonic vasculature, while littermate controls showed normal development.

CONCLUSIONS

Cigarette smoking during pregnancy is fatal for growing embryos. CSC may induce the remodeling of embryonic vasculature, leading to various pathologies.

Temporal processing in inferior colliculus and auditory cortex affected by high doses of salicylate

Speech recognition and language learning can be affected by both peripheral and central auditory system impairment. However, whether sensorineural hearing loss would affect central auditory processing is not clear. Recent studies found that salicylate not only affects outer hair cell motility in the cochlea, but also blocks GABAergic neuron activities in central nervous systems. This provides a good animal model to evaluate the role of sensorineural hearing loss and central inhibition in auditory temporal processing. In this study, gap prepulse inhibition (gap-PPI) of the acoustic startle reflex was used to measure effects of salicylate on gap detection acuity. Salicylate administration (250 mg/kg) resulted in a significant reduction in gap-PPI amplitude and an increased gap detection threshold at 50 dB SPL, but not at 60 or 80 dB SPL. To identify the physiological effects of salicylate on central auditory system function, the inferior colliculus (IC) and auditory cortex (AC) responses were measured from conscious rats with chronically implanted electrodes. Salicylate induced a significant increase of the gap-detection threshold in AC-evoked potentials, but not in the IC-evoked potentials. The AC gap-detection threshold shift was diminished measured at an equal sensational level. These results suggest that salicylate-induced temporal processing deficits may be due to peripheral hearing loss, not central disinhibition.

Anti-angiogenic and teratological activities associated with exposure to total particulate matter from commercial cigarettes

Angiogenesis and the embryonic movement (EM) pathway are evolutionarily conserved mechanisms, which are essential for embryonic development. Deviation in these processes from exposure to cigarette total particulate matter (TPM) may produce vascular, morphogenetic, and teratological disorders. The anti-angiogenic and teratogenic potential of TPM from commercially available cigarettes was studied. In vitro effects of TPM on angiogenesis were determined with different assays utilizing human umbilical vein endothelial cells (HUVEC). A chicken embryo model was used to demonstrate the in vivo effects of TPM on EM, vascular development, and organogenesis. The current study provides evidence that cigarette TPM plays an impeding role in endothelial cell proliferation, migration, tube formation, and sprouting, which are crucial factors in angiogenesis. Video recordings and kinematic analyses of the TPM exposed chicken embryos revealed a striking decrease in EM. Likewise, exposure of TPM to embryos resulted in ocular, mandibular, and abdominal hemorrhaging. Several teratologies including ectopia cordis, as well as bi-trunked and mammoth headed embryos were frequent findings among TPM treated embryos. These results are strongly reminiscent of morphogenetic and teratogenic deformities in TPM exposed embryos. This shows that cigarette smoking during pregnancy can be fatal to growing embryos. In addition, TPM may produce defective morphogenesis, leading to various pathologies.