Simulated Microgravity Subtlety Changes Monoamine Function across the Rat Brain

Abstract

Microgravity, one of the conditions faced by astronauts during spaceflights, triggers brain adaptive responses that could have noxious consequences on behaviors. Although monoaminergic systems, which include noradrenaline (NA), dopamine (DA), and serotonin (5-HT), are widespread neuromodulatory systems involved in adaptive behaviors, the influence of microgravity on these systems is poorly documented. Using a model of simulated microgravity (SMG) during a short period in Long Evans male rats, we studied the distribution of monoamines in thirty brain regions belonging to vegetative, mood, motor, and cognitive networks. SMG modified NA and/or DA tissue contents along some brain regions belonging to the vestibular/motor systems (inferior olive, red nucleus, cerebellum, somatosensorily cortex, substantia nigra, and shell of the nucleus accumbens). DA and 5-HT contents were reduced in the prelimbic cortex, the only brain area exhibiting changes for 5-HT content. However, the number of correlations of one index of the 5-HT metabolism (ratio of metabolite and 5-HT) alone or in interaction with the DA metabolism was dramatically increased between brain regions. It is suggested that SMG, by mobilizing vestibular/motor systems, promotes in these systems early, restricted changes of NA and DA functions that are associated with a high reorganization of monoaminergic systems, notably 5-HT.

Mechanisms Underlying Dopaminergic Regulation of Nicotine-Induced Kinetic Tremor

“…Meanwhile, in P/MO, nicotine elevated both dopamine and DOPAC levels by about 40–50%. Although the reason why nicotine elevated the DA level in P/MO remains uncertain, the effects of nicotine on dopamine neurons may involve its interactions with the serotonergic and/or noradrenergic systems ( Gros et al, 2021 ; Pierucci et al, 2022 ). Although we did not specifically measure the dopamine level in IO, it is of interest that nicotine increased the dopaminergic tone in the P/MO region containing IO that forms the olivo-cerebellar neural circuit regulating tremor induction ( Puschmann and Wszolek, 2011 ; Ohno et al, 2015a ; Kosmowska and Wardas, 2021 ).…”

Translation from Microgravity Research to Earth Application

“…The topic “Translation from Microgravity Research to Earth Application” comprises publications focusing on space life sciences, gravitational biology and space medicine [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. It covers publications reporting the impact of altered environmental conditions, such as microgravity (µ g ), cosmic radiation and isolation on organisms down to the level of cells [ 3 , 4 , 5 , 7 , 8 , 10 , 11 , 12 , 13 , 14 ].…”

“…The topic “Translation from Microgravity Research to Earth Application” comprises publications focusing on space life sciences, gravitational biology and space medicine [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. It covers publications reporting the impact of altered environmental conditions, such as microgravity (µ g ), cosmic radiation and isolation on organisms down to the level of cells [ 3 , 4 , 5 , 7 , 8 , 10 , 11 , 12 , 13 , 14 ]. In addition, the topic collects studies validating causal diagrams of human health risks for spaceflight [ 1 ], hypergravity studies [ 2 ] and investigations about the impact of extreme isolation in the Antarctica on the human body [ 6 ].…”

“…Two research articles focused on neurological changes induced by altered gravity conditions [ 2 , 12 ]. An in vitro study evaluated the impact of hypergravity to potentially modify key features of astrocyte reactivity [ 2 ].…”

“…This finding suggests hypergravity together with live-cell imaging as a tool for future studies with other cell types, organoids, 3D spheroids or ex vivo cultures [ 2 ]. The second neurological study used the hindlimb unloading model (HLU) to expose rats to s-µ g for seven days and focused on the distribution of monoamines in functional territories of the rat brain [ 12 ]. The analyses reveal remodeling of the 5-HT (serotonin; 5-hydroxytryptamine) system alone or in interaction with catecholaminergic systems, notably DA (dopamine).…”