Intrauterine Exposure to Chronic 22 kHz Sound Affects Inhibitory Avoidance and Serotonergic Parameters in Forebrain Areas of Dams and Rat Offspring

In the present study we evaluated the effects of chronic exposure to sounds at 22 kHz during pregnancy on the central serotonergic and behavioral parameters in Wistar rat dams after the suckling period and on their male rat offspring. In addition, we also assessed the effects of an acute 22 kHz sound, associated with the chronic intrauterine exposure, on the emotional responses of adult offspring. The primary hypothesis was that experiencing 22 kHz stimuli during an early stage of development would interfere with brain serotonergic parameters and, later, with the adult rat’s defensive responses. The corollary question was whether a 22 kHz sound exposure would differentially affect inhibitory avoidance and escape responses and central serotonergic parameters. Female rats were divided into four groups: non-pregnant control;non-pregnant chronic exposure;pregnant control;and pregnant chronic exposure. Male offspring were divided into four groups: chronic intrauterine sound exposure;acute sound exposure in adulthood;chronic intrauterine exposure with acute exposure in adulthood;and no exposure. Chronic sound exposure affected inhibitory avoidance and serotonergic parameters in female rats. For offspring, there was an interaction between chronic and acute sound exposure effects on inhibitory avoidance response but not on escape response. There were significant effects of chronic intrauterine exposure on serotonin turnover in the hippocampus and PFC of females. For offspring, the turnover was increased by chronic exposure only in PFC, and in amygdala it was increased by acute exposure. These results illuminate the potential of an early acoustic sound exposure for causing central serotonergic and emotional behavioral changes that can persist into later periods of life.

Validation of a HPLC Method for Quantification of Thiamine and Its Phosphate Esters in Rat Brain Tissue

The present data show a fast and efficient biological sample processing method for the extraction of thiamine (vitamin B1) and its mono-(TMP) and di-(TDP) phosphate esters from hippocampus, thalamus and prefrontal cortex (PFC) and blood sample of the rodents. In addition, using the hippocampus and standards of these three compounds we validated an isocratic fluorescence HPLC procedure for a simultaneous detection of them in a single chromatogram within a total run time of about 12 min. Reproducibility for TDP, TMP and B1 was 2.66%, 4.50% and 7.43% (intraday) and 37.54%, 25.39% and 25.87% (interday), respectively. Recovery assays were between 96.0% and 101.7%. The calibration curves were linear and the concentrations of the three compounds, all in nanomolar range, were determined in the brain areas and in the blood samples. When compared to the current methods in the literature, this new method provides information on essential variables, such as linearity range and limit of detection, reproducibility and stability of thiamine, TMP and TDP in rat brain samples. The present data on sample processing and B1 and its phosphate ester level determinations are the first to be validated using hippocampus samples of rats.