Identifying the In Vivo Cellular Correlates of Antipsychotic Drugs

Extra-forebrain impact of antipsychotics indicated by c-Fos or FosB/ΔFosB expression: A minireview

It is apparent that the c-Fos and FosB/ΔFosB immunohistochemistry has generally become a useful tool for determining the different antipsychotic (AP) drugs activities in the brain. It is also noteworthy that there are no spatial limits, while to the extent of their identification over the whole brain axis. In addition, they can be in a parallel manner utilized in the unmasking of the brain cell phenotype character activated by APs and by this way also to identify the possible brain circuits underwent to the APs action. However, up to date, the number of APs involved in the extra-striatal studies is still limited, what prevents the possibility to fully understand their extra-striatal effects as a complex as well as differentiate their extra-striatal impact in qualitative and quantitative dimensions. Actually, it is very believable that more and more anatomical/functional knowledge might bring new insights into the APs extra-striatal actions by identifying new region-specific activities of APs as well as novel cellular targets affected by APs, which might reveal more details of their possible side effects of the extra-striatal origin.

Redundancy and multifunctionality among spinal locomotor networks

c-Fos is used to identify system-wide neural activation with cellular resolution in vivo. However, c-Fos can only capture neural activation of one event. Targeted recombination in active populations (TRAP) allows the capture of two different c-Fos activation patterns in the same animal. So far, TRAP has only been used to examine brain circuits. This study uses TRAP to investigate spinal circuit activation during resting and stepping, giving novel insights of network activation during these events. The level of colabeled (c-Fos+ and TRAP+) neurons observed after performing two bouts of stepping suggests that there is a probabilistic-like phenomenon that can recruit many combinations of neural populations (synapses) when repetitively generating many step cycles. Between two 30-min bouts of stepping, each consisting of thousands of steps, only ∼20% of the neurons activated from the first bout of stepping were also activated by the second bout. We also show colabeling of interneurons that have been active during stepping and resting. The use of the FosTRAP methodology in the spinal cord provides a new tool to compare the engagement of different populations of spinal interneurons in vivo under different motor tasks or under different conditions.NEW & NOTEWORTHY The results are consistent with there being an extensive amount of redundancy among spinal locomotor circuits. Using the newly developed FosTRAP mouse model, only ∼20% of neurons that were active (labeled by Fos-linked tdTomato expression) during a first bout of 30-min stepping were also labeled for c-Fos during a second bout of stepping. This finding suggests variability of neural networks that enables selection of many combinations of neurons (synapses) when generating each step cycle.