ABSTRACT
In spite of the existing reports on behavioural and biochemical changes related to the cerebellum due to noise stress, not much is known about the effect of noise stress on the neuronal changes in the cerebellum. The present study aims at investigating the effects from one week noise exposure on granule cell number and Purkinje cell volume within the neonate rat cerebellum. 15-day-old male Wistar rats were randomly divided into noise exposed [NE] and control groups [n=8 in each group]. NE rats exposed to loud noise [100 dB/30 min/3 times per day] during the third postnatal week. One cerebellar half was selected at random for estimating the volume of the cerebellar layers and neuronal quantifications and the other was used for estimating individual somal volume of Purkinje cells. Cavalieri's principle, physical disector and nucleator methods were employed respectively for unbiased estimation of the volumes of the cerebellar layers, the numerical density of neurons and the individual volume of Purkinje cells. Results of this study show that noise stress significantly decreases the volume of granule layer together with decreased numerical density and total number of granule cells in the cerebellum. Furthermore, a decrease in somal volume of Purkinje cells was found in NE rats. These results, for the first time, demonstrate an effect of noise stress on the granule cell number and individual volume of Purkinje cells in rat cerebellum
ABSTRACT
The hippocampal circuit integrity is crucial for learning and memory. Despite the existing reports on hippocampal_dependent memory impairment due to noise stress, there are only a few studies on the effect of noise stress on anatomical structure of hippocampus. The present study is aimed to investigate the likely effects of chronic noise exposure on the volume of rat hippocampus. Two-month male Wistar rats were randomly divided into three groups [n=10 in each group]. In the control group rats were maintained under standard laboratory conditions [150 days]. In the noise-exposed group: Rats were exposed to 40 dB unmodulated sinosoidal noise with a frequency of 1100 Hz for 20 mins, three times per day for 90 days. The recovery group rats were exposed to noise for 90 days and allowed to survive without further treatment until the day of sacrifice [180th day]. The right hemispheres were selected for stereological study. Twenty five mm thick sections were cut along the entire extent of the hippocampus. Using systematic uniformly random sampling, one section from every twenty sections was analyzed. Volume estimation was performed using Cavalieri principle. Statistical analysis revealed that noise stress induces a significant reduction in volume of all layers of hippocampal subdivisions, except CA1 hippocampal field. In addition, we found that rats which were allowed to recover from noise displayed larger volume of dentate gyrus and CA3 hippocampal field in comparison to noise-exposed rats. Reduced volume of hippocampal layers most probably reflects structural alterations in the neurites of related neurons. These results provide a neuroanatomical basis that may be relevant to the reported memory disturbances in human and animals following noise stress