The Beauty of the Dopamine system

Ex-vivo Slice Electrophysiology (commonly known as ‘patching’) is a technique whereby we insert a tiny patch pipet into a neuron in order to record from it. It’s a very involved process that requires a lot of practice. Patching your first neuron is generally cause for cellebration. I’ve used slice electrophysiology to study the effects of cocaine administration on synaptic plasticity on projection-defined dopamine neurons. Since it was important to me to be able to identify which exact neuron I recorded from, I filled my pipets with a dye called biocytin. While recording from dopamine neurons the biocytin difuses into the cell, which allowed me to later inspect the cell underneath a microscope. The images below are all dopamine neurons obtained in this matter. They are in a brain area between the brain stem and the cerebrum called the Ventral Tegmental Area (VTA).

The VTA is one of two major sources of dopamine in the brain. The other source is the Substantia Nigra (SN, ‘black substance’) which contains the dopamine neurons that are affected in Parkinson’s disease. I’m specifically interested in the VTA, because we know that that the dopamine neurons in the VTA are affected in drug addiction. VTA dopamine neurons are not a homogeneous population, different dopamine neurons are differently involved in behavior and have specific projection targets throughout the brain. In the picture below I used a pseudo-typed rabies virus to specifically label dopamine neurons that project from the ventral-medial part of the VTA to the ventral-medial part of the Nucleus Accumbens (A brain region known to be involved in reward processing). The cells in the background (in red) are all dopamine neurons as well, but they most likely project to different brain regions.

The nucleus accumbens is a major site of dopamine release in the brain. We think that dopamine release in this nucleus plays an important role in reward processing and learning. In the picure bellow I again used pseudo-typed rabies virus to map neural pathways. In this case I mapped the connection from the hippocampus (a brain region important for memorry and spacial awareness) to the nucleus accumbens. The picture was published in Interstellate, volume 1.