​The exchange of ions across neuronal membranes gives rise to an “electric discharge”, namely an action potential that determines the passage of nerve impulses from one neuron to the next. The issue for microscopic imaging is to follow the dynamics of these exchanges along neuronal circuits in different biochemical conditions. Such studies are opening a new field of investigation to cognitive neuroscience and drug development. Thanks to NeuroSpin’s high-field MRI device (17.2 Tesla) dedicated to small animals, teams from the CEA-I²BM are developing imaging techniques in living cells to bridge the results between biological imaging on tissue sections and in vivo imaging. The first offers a spatial resolution of about 10 microns [1], while the second has a resolution from 100 – 200 microns.

The researchers worked with Aplysia, a classic model animal in neuroscience with a small set of large neurons (from several hundred microns to 1 mm in size). The neurons are therefore also observable by high-resolution in vivo imaging. The scientists have shown for the first time that the dynamics of transporting manganese ions (analogous to calcium) in the motor neurons of the Aplysia buccal ganglion are modulated by the neurotransmitter dopamine. To do this, they used high-field MRI to observe Aplysia neurons in medium with a low manganese concentration, so as to not disrupt cell physiology. They showed that stimulation of neurons with dopamine alters the dynamics of manganese ions, particularly their elimination by neurons. This is the first time that such a modulation is revealed in a network where each neuron is visible by MRI, thanks to its very advanced spatial resolution.

The exchange of ions across neuronal membranes gives rise to an “electric discharge”, namely an action potential that determines the passage of nerve impulses from one neuron to the next. The issue for microscopic imaging is to follow the dynamics of these exchanges along neuronal circuits in different biochemical conditions. Such studies are opening a new field of investigation to cognitive neuroscience and drug development. Thanks to NeuroSpin’s high-field MRI device (17.2 Tesla) dedicated to small animals, teams from the CEA-I²BM are developing imaging techniques in living cells to bridge the results between biological imaging on tissue sections and in vivo imaging. The first offers a spatial resolution of about 10 microns [1], while the second has a resolution from 100 – 200 microns.

The researchers worked with Aplysia, a classic model animal in neuroscience with a small set of large neurons (from several hundred microns to 1 mm in size). The neurons are therefore also observable by high-resolution in vivo imaging. The scientists have shown for the first time that the dynamics of transporting manganese ions (analogous to calcium) in the motor neurons of the Aplysia buccal ganglion are modulated by the neurotransmitter dopamine. To do this, they used high-field MRI to observe Aplysia neurons in medium with a low manganese concentration, so as to not disrupt cell physiology. They showed that stimulation of neurons with dopamine alters the dynamics of manganese ions, particularly their elimination by neurons. This is the first time that such a modulation is revealed in a network where each neuron is visible by MRI, thanks to its very advanced spatial resolution.

[1] 1 micron= 10^-6 meter