Brain slice preparations have enabled investigators to make intracellular/whole-cell patch recordings from neurons while applying pharmacological agents but have a disadvantage in that the normal flow of information in neural circuits is disrupted. To test the acute effect of a compound on an individual neuron or the effect of pre-treatment with a drug on the spontaneous firing activity and firing rate of multiple neurons, Acroscell performs a variety of in vivo single-cell recording studies.
Neurons from various parts of the brain can be recorded, including:
Dopamine (substantia nigra and ventral tegmental area)
Histamine (tuberomammillary nucleus)
Norepinephrine (locus coeruleus)
Glutamate pyramidal neurons (prefrontal cortex/hippocampus)
Serotonin (medial raphe nucleus and dorsal raphe nucleus)
Fig. 1 Whole cell and extracellular in vivo recordings of CNs before, during, and after optogenetic activation of PCs
In vivo single unit recordings can be done either intracellularly or extracellularly. While extracellular recordings can only give spike information, intracellular single unit recordings can give information on sub-threshold information, resting potentials and postsynaptic potentials. The use of either technique depends on the specific application and what information is desired.
Intracellular single unit recordings provide much more information on single neuron discharges. They can give information on steady and resting membrane voltage, postsynaptic potentials, and spikes (action potentials) from both the axon and cell body.
Extracellular single unit recordings are more suitable for measuring extracellular action potentials. Extracellular recordings can easily measure spike discharge from a neuron with any suitably small electrode. This makes it much easier to obtain these signals in an awake and moving animals.
This involves careful placement of extracellular and intracellular electrodes in a single neuron. The primary use for this is to provide a better understanding of the relationship between intracellular action potentials and extracellular spike recordings.
Witter L, et al. Strength and timing of motor responses mediated by rebound firing in the cerebellar nuclei after Purkinje cell activation. Frontiers in neural circuits. 2013, 7: 133.