Stereological Estimation of Granule Cell Number and Purkinje Cell Volume in the Cerebellum of Noise-Exposed Young Rat

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.