Exposição crônica maternal a sons de 22 kHz altera a resposta de esquiva inibitória sem afetar a fuga e altera parâmetros serotoninérgicos centrais das mães e da prole na idade adulta

Abstract

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 rats defensive responses. The corollary question was whether a 22 kHz sound exposure would differentially affect inhibitory avoidance and escape responses and central serotonergic parameters. In this 2x2 study the factors were: (i) for dams - a chronic sound exposure and pregnant state per se, (ii) for offspring - a chronic intrauterine sound exposure and an acute 22 kHz sound exposure in adulthood. Thirty-two female Wistar rats were divided into four groups of eight: non-pregnant control; non-pregnant chronic exposure; pregnant control; and pregnant chronic exposure. Forty-eight male offspring were divided into four groups of twelve: chronic intrauterine sound exposure; acute sound exposure in adulthood; chronic intrauterine exposure with acute exposure in adulthood; and no exposure treatment (control). Learning, memory, anxiety and fear states were assessed through inhibitory avoidance and escape tasks, using an Elevated T-Maze. Serotonergic parameters (5-HT and 5-HIAA levels) were determined in the hippocampus, amygdala, periaquedutal grey area and prefrontal cortex (PFC). Chronic sound exposure affected inhibitory avoidance and serotonergic parameters in female rats. For offspring, there was an interaction between the factors (chronic and acute sound exposures) on inhibitory avoidance response but not on escape response. Both treatments decreased 5-HIAA concentrations in the hippocampus. An interaction between the treatments was also found for 5-HIAA levels in the hippocampus and amygdala. There were significant effects of intrauterine and acute 22 kHz exposure on 5-HT turnover rate in PFC and amygdala of the offspring rats. These results illuminate the potencial of an early acoustic sound exposure for causing central serotonergic and emotional behavioral changes that can persist into later periods of life. Besides, the present data also show that the 22 kHz sound exposure represents a useful tool for understanding the mechanism of a specific defensive behavior. That is, as the 22 kHz sound exposure affects inhibitory avoidance but not escape behavior, it might be relevant for clarifying physiological and molecular aspects of emotion.