DSpace Collection:
https://hdl.handle.net/10171/17879
2024-03-28T15:49:23ZNeuroanatomical tract-tracing techniques that did go viral
https://hdl.handle.net/10171/66470
Title: Neuroanatomical tract-tracing techniques that did go viral
Abstract: Neuroanatomical tracing methods remain fundamental for elucidating the complexity of brain circuits. During the past
decades, the technical arsenal at our disposal has been greatly enriched, with a steady supply of fresh arrivals. This paper
provides a landscape view of classical and modern tools for tract-tracing purposes. Focus is placed on methods that have
gone viral, i.e., became most widespread used and fully reliable. To keep an historical perspective, we start by reviewing
one-dimensional, standalone transport-tracing tools; these including today’s two most favorite anterograde neuroanatomical tracers such as Phaseolus vulgaris-leucoagglutinin and biotinylated dextran amine. Next, emphasis is placed on several
classical tools widely used for retrograde neuroanatomical tracing purposes, where Fluoro-Gold in our opinion represents
the best example. Furthermore, it is worth noting that multi-dimensional paradigms can be designed by combining diferent
tracers or by applying a given tracer together with detecting one or more neurochemical substances, as illustrated here with
several examples. Finally, it is without any doubt that we are currently witnessing the unstoppable and spectacular rise of
modern molecular-genetic techniques based on the use of modifed viruses as delivery vehicles for genetic material, therefore,
pushing the tract-tracing feld forward into a new era. In summary, here, we aim to provide neuroscientists with the advice
and background required when facing a choice on which neuroanatomical tracer—or combination thereof—might be best
suited for addressing a given experimental design.2020-01-01T00:00:00ZCholinergic midbrain afferents modulate striatal circuits and shape encoding of action strategies
https://hdl.handle.net/10171/65628
Title: Cholinergic midbrain afferents modulate striatal circuits and shape encoding of action strategies
Abstract: Assimilation of novel strategies into a consolidated action repertoire is a crucial function for
behavioral adaptation and cognitive flexibility. Acetylcholine in the striatum plays a pivotal
role in such adaptation, and its release has been causally associated with the activity of
cholinergic interneurons. Here we show that the midbrain, a previously unknown source of
acetylcholine in the striatum, is a major contributor to cholinergic transmission in the striatal
complex. Neurons of the pedunculopontine and laterodorsal tegmental nuclei synapse with
striatal cholinergic interneurons and give rise to excitatory responses. Furthermore, they
produce uniform inhibition of spiny projection neurons. Inhibition of acetylcholine release
from midbrain terminals in the striatum impairs the association of contingencies and the
formation of habits in an instrumental task, and mimics the effects observed following
inhibition of acetylcholine release from striatal cholinergic interneurons. These results suggest the existence of two hierarchically-organized modes of cholinergic transmission in the
striatum, where cholinergic interneurons are modulated by cholinergic neurons of the
midbrain.2020-01-01T00:00:00ZMidbrain microglia mediate a specific immunosuppressive response under inflammatory conditions
https://hdl.handle.net/10171/63787
Title: Midbrain microglia mediate a specific immunosuppressive response under inflammatory conditions
Abstract: Background: Inflammation is a critical process for the progression of neuronal death in neurodegenerative
disorders. Microglia play a central role in neuroinflammation and may affect neuron vulnerability. Next generation
sequencing has shown the molecular heterogeneity of microglial cells; however, the variability in their response to
pathological inputs remains unknown.
Methods: To determine the effect of an inflammatory stimulus on microglial cells, lipopolysaccharide (LPS) was
administered peripherally to mice and the inflammatory status of the cortex, hippocampus, midbrain, and striatum
was assessed. Microglial activation and interaction with the immune system were analyzed in single cell
suspensions obtained from the different brain regions by fluorescence-activated cell sorting, next generation RNA
sequencing, real-time PCR, and immunohistochemical techniques. Antigen-presenting properties of microglia were
evaluated by the ability of isolated cells to induce a clonal expansion of CD4+ T cells purified from OT-II transgenic
mice.
Results: Under steady-state conditions, the midbrain presented a high immune-alert state characterized by the
presence of two unique microglial subpopulations, one expressing the major histocompatibility complex class II
(MHC-II) and acting as antigen-presenting cells and another expressing the toll-like receptor 4 (TLR4), and by the
presence of a higher proportion of infiltrating CD4+ T cells. This state was not detected in the cortex, hippocampus,
or striatum. Systemic LPS administration induced a general increase in classic pro-inflammatory cytokines, in coinhibitory programmed death ligand 1 (PD-L1), and in cytotoxic T lymphocyte antigen 4 (CTLA-4) receptors, as well
as a decrease in infiltrating effector T cells in all brain regions. Interestingly, a specific immune-suppressive response
was observed in the midbrain which was characterized by the downregulation of MHC-II microglial expression, the
upregulation of the anti-inflammatory cytokines IL10 and TGFβ, and the increase in infiltrating regulatory T cells.
Conclusions: These data show that the midbrain presents a high immune-alert state under steady-state conditions
that elicits a specific immune-suppressive response when exposed to an inflammatory stimulus. This specific
inflammatory tone and response may have an impact in neuronal viability2019-01-01T00:00:00ZSparse force‑bearing bridges between neighboring synaptic vesicles
https://hdl.handle.net/10171/62936
Title: Sparse force‑bearing bridges between neighboring synaptic vesicles
Abstract: Most vesicles in the interior of synaptic terminals are clustered in clouds close to active zone regions of the plasma membrane
where exocytosis occurs. Electron-dense structures, termed bridges, have been reported between a small minority of pairs of
neighboring vesicles within the clouds. Synapsin proteins have been implicated previously, but the existence of the bridges
as stable structures in vivo has been questioned. Here we use electron tomography to show that the bridges are present but
less frequent in synapsin knockouts compared to wildtype. An analysis of distances between neighbors in wildtype tomograms indicated that the bridges are strong enough to resist centrifugal forces likely induced by fxation with aldehydes. The
results confrm that the bridges are stable structures and that synapsin proteins are involved in formation or stabilization.2019-01-01T00:00:00Z