Serotonin metabolism in directly developing frog embryos during paternal care

Serotonin turnover in different duration of sleep recovery in discrete regions of young rat brain after 24 h REM sleep deprivation

Sleep plays an important role in restorative function and serotonin (5-hydroxytryptamine: 5HT) equally plays important roles in sleep. Though various studies have revealed the roles of 5HT in sleep/wake cycle, the mechanism involved is yet unclear. In the present study we investigated alteration of the 5HT turnover in various regions of the young rat brains after 24 hours (h) REM sleep (sREM) deprivation to elucidate the roles of 5HT in sleep restoration function in the these regions. The 5HT turnover was evaluated by the ratio of 5-hydroxyindole acetic acid against 5HT. The sREM deprivation was performed by the inverted flowerpot technique. The 5HT turnover showed significant alteration in the all regions of the brain examined after 24h sREM deprivation, particular depending on the brain region. These results revealed that sREM modulates the 5HT turnover in the brain with region specificity and this may be one of the restorative functions of sleep indicating that sREM is regionally generated.

Ontogeny of central serotonergic neurons in the directly developing frog, Eleutherodactylus coqui

Embryonic development of the central serotonergic neurons in the directly developing frog, Eleutherodactylus coqui, was determined by using immunocytochemistry. The majority of anuran amphibians (frogs) possess a larval stage (tadpole) that undergoes metamorphosis, a dramatic post-embryonic event, whereby the tadpole transforms into the adult phenotype. Directly developing frogs have evolved a derived life-history mode where the tadpole stage has been deleted and embryos develop directly into the adult bauplan. Embryonic development in E. coqui is classified into 15 stages (TS 1-15; 1 = oviposition/15 = hatching). Serotonergic immunoreactivity was initially detected at TS 6 in the raphe nuclei in the developing rhombencephalon. At TS 7, immunopositive perikarya were observed in the paraventricular organ in the hypothalamus and reticular nuclei in the hindbrain. Development of the serotonergic system was steady and gradual during mid-embryogenesis. However, starting at TS 13 there was a substantial increase in the number of serotonergic neurons in the paraventricular, raphe, and reticular nuclei, a large increase in the number of varicose fibers, and a differentiation of the reticular nuclei in the hindbrain. Consequentially, E. coqui displayed a well-developed central serotonergic system prior to hatching (TS 15). In comparison, the serotonergic system in metamorphic frogs typically starts to develop earlier but the surge of development that transpires in this system occurs post-embryonically, during metamorphosis, and not in the latter stages of embryogenesis, as it does in E. coqui. Overall, the serotonergic development in E. coqui is similar to the other vertebrates.