Regional and seasonal variations of RNA synthesis in the brain of the green frog, Rana esculenta

• Published in: European journal of histochemistry Vol. 38; no. 3; pp. 193 - 202
• Main Authors: Chieffi Baccari, G, Minucci, S, Chieffi, G
• Format: Journal Article
• Language: English
• Published: Italy 1994
• Subjects: Animals; Autoradiography; Brain - metabolism; Ependyma - metabolism; Female; Hibernation; Histocytochemistry; Male; Neurons - metabolism; Photoperiod; Rana esculenta; RNA - biosynthesis; Seasons; Temperature
• ISSN: 1121-760X

Changes of RNA synthesis were demonstrated in neurons and ependymal cells of the green frog Rana esculenta during the annual cycle using the Mallory's trichrome stain as histochemical marker and autoradiography. Since the higher affinity of the nuclei for aniline blue is consistent with the increase of RNA content, the increase of RNA synthesis was expressed as percentage of the blue stained nuclei (% BSN). Neuronal transcription starts slowly in March or April, reaches a maximum in July and declines from September to November or December, depending on the brain region. In the ependymal cells, RNA synthesis starts in March and lasts until October. Neuronal transcriptional activity is found mostly in the glomerular layer of the olfactory bulb, in the striatum, nucleus accumbens septi, lateral and medial septal nuclei of the telencephalon, in the habenulae and various nuclei of the diencephalon, in the tectum opticum (particularly in the stratum griseum centrale), in the molecular layer of the cerebellum and in various nuclei of the rhombencephalon. The transcriptional activity of the ependymal cells is quite uniform in the lateral ventricles and the fourth ventricle, while it shows regional symmetric distribution in the third ventricle. Seasonal differences in transcriptional activity appear to be independent of seasonal thermic and photoperiodic fluctuations. In fact, temperature and photoperiod manipulations do not modify significantly the number of active nuclei. It is likely that the increase of RNA synthesis in nerve and ependymal cells corresponds to the resumption of neurotransmitter biosynthesis after hibernation. The simple Mallory's trichrome stain provides a reliable method for revealing increased transcriptional activity in histological sections.