Prenatal IV Cocaine: Alterations in Auditory Information Processing

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.

Antidepressants and risk of sudden sensorineural hearing loss: a population-based cohort study

BACKGROUND

Increasing numbers of animal studies have found that sudden sensorineural hearing loss (SSNHL) is related to the mechanism of serotonergic modulation. However, the relationship between antidepressants and SSNHL is unclear in humans. Therefore, this study aimed to evaluate the association between antidepressant use and risk of SSNHL.

METHODS

Data from 218 466 antidepressant users and 1 116 518 nonusers were obtained from the Taiwan Longitudinal Health Insurance Database. We used propensity-score matching (PSM) and inverse-probability treatment weighting (IPTW) to eliminate any bias. Each patient was tracked for 5 years to ascertain whether or not they were diagnosed with SSNHL. Cox proportional-hazard regression analyses were performed to calculate the SSNHL risk.

RESULTS

The adjusted hazard ratio (aHR) of SSNHL for antidepressant users was 1.36 compared with nonusers in the full cohort study. The aHR for antidepressant users was 1.44 and 1.49 compared with the nonusers in the IPTW and PSM cohorts, respectively. All classes of antidepressants consistently increased the SSNHL risk. Additionally, patients receiving four classes of antidepressants were associated with a much higher SSNHL risk (aHR, 2.05) and those receiving one or two classes of antidepressants had a relatively lower SSNHL risk.

CONCLUSION

Antidepressants increased SSNHL risk, regardless of their class. Furthermore, patients who took a higher number of antidepressant classes showed an increased risk of developing SSNHL than those who took a lower number of antidepressant classes. Therefore, physicians should estimate the risks and benefits of antidepressant use and avoid prescribing antidepressants concurrently.

Reference compounds for alternative test methods to indicate developmental neurotoxicity (DNT) potential of chemicals: example lists and criteria for their selection and use

There is a paucity of information concerning the developmental neurotoxicity (DNT) hazard posed by industrial and environmental chemicals. New testing approaches will most likely be based on batteries of alternative and complementary (non-animal) tests. As DNT is assumed to result from the modulation of fundamental neurodevelopmental processes (such as neuronal differentiation, precursor cell migration or neuronal network formation) by chemicals, the first generation of alternative DNT tests target these processes. The advantage of such types of assays is that they capture toxicants with multiple targets and modes-of-action. Moreover, the processes modelled by the assays can be linked to toxicity endophenotypes, i.e. alterations in neural connectivity that form the basis for neurofunctional deficits in man. The authors of this review convened in a workshop to define criteria for the selection of positive/negative controls, to prepare recommendations on their use, and to initiate the setup of a directory of reference chemicals. For initial technical optimization of tests, a set of >50 endpoint-specific control compounds was identified. For further test development, an additional “test” set of 33 chemicals considered to act directly as bona fide DNT toxicants is proposed, and each chemical is annotated to the extent it fulfills these criteria. A tabular compilation of the original literature used to select the test set chemicals provides information on statistical procedures, and toxic/non-toxic doses (both for pups and dams). Suggestions are provided on how to use the >100 compounds (including negative controls) compiled here to address specificity, adversity and use of alternative test systems.

The role of sensory modality in prepulse inhibition: An ontogenetic study

Deficits in prepulse inhibition (PPI), a measure of sensorimotor gating, are observed in neurodevelopmental and neuropsychiatric disorders. Despite the large PPI literature, the majority of studies characteristically employ tests with one interstimulus interval (ISI), of one modality, at one age. In the context of the auditory startle response (ASR), the present study examined (1) the profile for the ontogeny of PPI through adulthood in Long-Evans hooded rats with a reasonably comprehensive ISI function, (2) whether the ontogenetic profile for PPI is sensitive to modality of the prepulse stimulus, as a within-session variable, and (3) whether the maturation of PPI differs for males and females. Despite the basic effect of more pronounced PPI in adult relative to preweanling animals, each sensory modality displayed a unique ontogenetic profile for PPI, without any compelling evidence for major differences between males and females, in accordance with the known temporal course of peripheral and central maturational profiles of sensory systems in the rat. The context for assessing auditory PPI (auditory and tactile vs. auditory and visual prepulses) influenced the overall startle response, i.e., a shift in the height of the entire profile, but did not significantly impact the auditory PPI profile per se. The translational relevance of preclinical sensorimotor assessments to patients with neurodevelopmental and/or neuropsychiatric disorders depends partly on an understanding of the ontogeny of sensorimotor gating in different sensory systems, and can be strengthened with the use of a reasonably comprehensive number of ISIs to provide relatively precise and defined response functions.

Level of intrauterine cocaine exposure and neuropsychological test scores in preadolescence: subtle effects on auditory attention and narrative memory

Neuropsychological processes such as attention and memory contribute to children's higher-level cognitive and language functioning and predict academic achievement. The goal of this analysis was to evaluate whether level of intrauterine cocaine exposure (IUCE) alters multiple aspects of preadolescents' neuropsychological functioning assessed using a single age-referenced instrument, the NEPSY: A Developmental Neuropsychological Assessment (NEPSY) (Korkman et al., 1998), after controlling for relevant covariates. Participants included 137 term 9.5-year-old children from low-income urban backgrounds (51% male, 90% African American/Caribbean) from an ongoing prospective longitudinal study. Level of IUCE was assessed in the newborn period using infant meconium and maternal report. 52% of the children had IUCE (65% with lighter IUCE, and 35% with heavier IUCE), and 48% were unexposed. Infants with Fetal Alcohol Syndrome, HIV seropositivity, or intrauterine exposure to illicit substances other than cocaine and marijuana were excluded. At the 9.5-year follow-up visit, trained examiners masked to IUCE and background variables evaluated children's neuropsychological functioning using the NEPSY. The association between level of IUCE and NEPSY outcomes was evaluated in a series of linear regressions controlling for intrauterine exposure to other substances and relevant child, caregiver, and demographic variables. Results indicated that level of IUCE was associated with lower scores on the Auditory Attention and Narrative Memory tasks, both of which require auditory information processing and sustained attention for successful performance. However, results did not follow the expected ordinal, dose-dependent pattern. Children's neuropsychological test scores were also altered by a variety of other biological and psychosocial factors.