The investigation of the embryonic development of the cerebellum has a long history. The postnatal normal development of the cerebellum in rodents and other animals became a popular topic for morphological investigations nearly a century ago. However, surprisingly, only a few studies are available regarding the prenatal normal development of the rodent cerebellum, especially in guinea pigs. Cell proliferation is essential for the development of the nervous system. The assessment of cell proliferation can be achieved by using various methods. In this study, we investigated the cell proliferation of the cerebellar cortex in guinea pigs at different stages of pregnancy and in postnatal life. Fetuses were obtained by cesarean section at 50 or 60 days of gestation (dg). Immunohistochemistry was performed with proliferating cell nuclear antigen (PCNA) antibody in the cerebellum. Strong PCNA immunoreactivity was observed in the external granular layer (EGL), which is a neurogenic zone in the cerebellum. The proportion of PCNA-IR cells was greater at 1 week than at 60 dg in lobule I, but not lobule VIII. After 50 dg, the width of the EGL continued to decline until 1 week, due to the maturation of the EGL cells. These results demonstrate the pattern of PCNA immunoreactivity in the developing cerebellum of guinea pigs. This serves as a guideline to study abnormal cerebellum development.

Sucrose and alcohol are rewarding and appetitive. They are occasionally over-consumed and cause addiction. The parabrachial nuclei (PbN) are the second taste relay in the central taste pathway. The nucleus accumbens (NAcc) is an important neural substrate in the reward system. Intake of sucrose or alcohol induces dopamine release in the NAcc. Although alcohol is not classified as a taste stimulus, a substantial number of sucrose-responsive neurons in the PbN respond to stimulation by alcohol on the tongue. In the present study, we investigated whether or not application of 0.5 M sucrose, 10% ethanol (EtOH), mixture of sucrose and EtOH, and double-distilled water (DDW) to the tongue induces c-Fos-like immunoreactivity (cFLI) in the PbN and NAcc. We also examined whether or not the number of cFLI following sucrose/EtOH is comparable to the number of cFLIs following sucrose and EtOH, respectively. Male Sprague-Dwaley rat was anesthetized with a mixture of Zoletil and Rompun while stimulation solution was applied to the anterior tongue. The rat was sacrificed by perfusion, and the fixed brain was sectioned and immunostained. Data from a total of 18 animals were analyzed. The number of cFLI following stimulation with sucrose and/or EtOH was greater than that of DDW in the PbN. Numbers of cFLI following sucrose, EtOH, and sucrose/EtOH were not significantly different from each other in the PbN. The number of cFLI in response to stimulation solution was not different from that of DDW in the NAcc. The result of the present study suggests that not only sucrose but also EtOH activates some neurons in the PbN, and that some pontine neurons possibly respond to both sucrose and EtOH.

Taste receptors of the anterior tongue are innervated by the chorda tympani (CT) branch of the facial (VIIth) nerve. The CT nerve transmits information on taste to the ipsilateral nucleus of the solitary tract (NST), which is the first taste central nucleus in the medulla. Taste information is known to be transferred ipsilaterally along the taste pathway in the central nervous system. Some patients with unilateral CT damage often retain their ability to sense taste. This phenomenon is not explained by the unilateral taste pathway. We examined whether neurons in the NST receive information on taste from the contralateral side of the tongue by measuring c-Fos-like Immunoreactivity (cFLI) following taste stimulation of the contralateral side of the tongue in the anesthetized rats. We used four basic taste stimuli, 1.0 M sucrose, 0.3 M NaCl, 0.01 M citric acid, 0.03 M QHCl, and distilled water. Stimulation of one side of the tongue with taste stimuli induced cFLI in the NST bilaterally. The mean number of cFLI ranged from 23.28 ± 2.46 by contralateral QHCl to 30.28 ± 2.26 by ipsilateral NaCl stimulation. The difference between the number of cFLI in the ipsilaterl and contralateral NST was not significant. The result of the current study suggests that neurons in the NST receive information on taste not only from the ipsilateral but also the contralateral side of the tongue.