Transcriptomic analysis of dorsal and ventral subiculum after induction of acute seizures by electric stimulation of the perforant pathway in rats.

Preconditioning is a mechanism in which injuries induced by non-lethal hypoxia or seizures trigger cellular resistance to subsequent events. Norwood et al., in a 2010 study, showed that an 8-h-long period of electrical stimulation of the perforant pathway in rats is required for the induction of hippocampal sclerosis. However, in order to avoid generalized seizures, status epilepticus (SE), and death, a state of resistance to seizures must be induced in the hippocampus by a preconditioning paradigm consisting of two daily 30-min stimulation periods. Due to the importance of the subiculum in the hippocampal formation, this study aims to investigate differential gene expression patterns in the dorsal and ventral subiculum using RNA-sequencing, after induction of a preconditioning protocol by electrical stimulation of the perforant pathway. The dorsal (dSub) and ventral (vSub) subiculum regions were collected by laser-microdissection 24 h after preconditioning protocol induction in rats. RNA sequencing was performed in a Hiseq 4000 platform, reads were aligned using the STAR and DESEq2 statistics package was used to estimate gene expression. We identified 1176 differentially expressed genes comparing control to preconditioned subiculum regions, 204 genes were differentially expressed in dSub and 972 in vSub. The gene ontology enrichment analysis showed that the most significant common enrichment pathway considering up-regulated genes in dSub and vSub was steroid metabolism. In contrast, the most significant enrichment pathway considering down-regulated genes in vSub was axon guidance. Our results indicate that preconditioning induces changes in the expression of genes related to synaptic reorganization, increased cholesterol metabolism, and astrogliosis in both dSub and vSub. Both regions also presented a decrease in the expression of genes related to glutamatergic transmission and an increase in expression of genes related to complement system activation and GABAergic transmission. The down-regulation of proapoptotic and axon guidance genes in the ventral subiculum suggests that preconditioning may induce a neuroprotective environment in this region.

Using the Parafilm-assisted Microdissection (PAM) Method to Sample Rodent Nucleus Accumbens.

Microdissection techniques are very important for anatomical and functional studies focused on neuroscience, where it is often necessary microdissect specific brain areas to perform molecular or anatomical analyses. The parafilm®-assisted microdissection (PAM) was previously described and involves the microdissection of tissue sections mounted on parafilm-covered glass slides. In this work, we describe the use of the PAM method to microdissect rodent nucleus accumbens (NAc). (1) We first describe the best way to perform the mouse euthanasia and how to remove the brain. (2) Next, we describe how to prepare the slides with parafilm® that will be used to receive the brain slices. (3) Following, we describe how to handle the brain in the cryostat, how to align the hemispheres and how to identify the NAc antero-posterior limits. (4) We also describe how to perform the staining and dehydration of the slices, a critical step to facilitate the microdissection and preserve macromolecules. (5) In the final step, we describe how to identify the dorso-ventral and latero-medial limits of the NAc and, finally, how to perform the manual microdissection of the area. This is a low-cost technique that allows the researcher to specifically microdissect any brain region, from which intact RNA and proteins can be extracted to perform several molecular analyses (e.g., real-time PCR, Western blot, and RNA-seq).