Hi Anu,

There are several antibodies that you can use to demarcate the patch/matrix compartments of striatum. This could be done after recording in vitro, do you fill your neurons after recording? You could use, for example, an antibody against the mu opioid receptor, which is enriched in the patches.

However, bear in mind that about 90% of the striatum is matrix and only 10% is patches, therefore the variability you see in your data between slices may not be accounted for by the patch/matrix organisation; there are several other factors that may contribute to this. 

Another method to see if you are in patch/matrix before recording would be to use a transgenic animal which reports selective genes that are located in either patch or matrix. You could then use fluorescence imaging before recording to bias your recording to either patch or matrix. This reference may be useful PMID: 24360541. 

Hi Anu,

There is indeed a bit of variability when recording from medium spiny neurons, and especially when you are doing pharmachology. As Natalie Said, it is unlikely that those differences are due to patch/matrix differences - however if you are willing to test that, you can fill your recorded neurons with biocytin and do immunohistochemistry afterwards (unless you have access to transgenic animals, which is obviously a more expensive solution). Are you able to identify whether you are recording from D1- or D2-positive MSNs? That could also acount for some variability. Again if you don't have access to transgenic animals, you can fill the recorded cells with biocytin and do immunohistochemistry for D1 and D2. Another possibility could also be that you are recording from more rostral or caudal slices, which can have differences in neurochemical environment and interneuron populations. Finally, if you are working with drugs that affect neuromodulator systems, you must bear in mind that their effects are quite variable, depending on the state of each slice - This last is more difficult as you'll probably need to do more experiments and you may need to group your data according to certain parameters so that you can make sense of them.

Best of luck!

Thanks Natalie and Samira,

I would keep your suggestions in mind while doing the recordings. I thought about that the difference is due to compartment because I see the variability in around 20% of the recordings. As you mentioned these differences could also be due to rostro-caudal position. I remember that while recording from the very rostral tip of striatum the results were amazingly different.

Besides what was mentioned above, it is important to consider what type of slice are you using, the age-range and if you are using extracellular (field) stimulation and/or intracellular current injection. If you use coronal slices there will be a huge variability in the preservation of the afferents to the striatum. In the frontal area, fibers are evident, but caudally, you mainly see sort of ovals because fibers were cut perpendicularly to their main axes. In my experience and from information reported by others, horizontal-oblique and parasagittal slices better preserve afferents to the striatum.

Age-wise, the younger the animal the closer the ages should be to avoid seeing differences due to developmental changes (like maturation of dendritic processes which in turn affect electrophysiological properties: internal resistance, capacitance, firing properties threshold, frequency, etc). For example, you could find huge differences between animals a few days apart in these and other properties if animals are younger than 10 days old. Instead, there will be little differences, if  any, when recording adults of, lets say, 2 vs. 3 months of age.

Regarding afferents and field stimulation to excite those projections, the type of afferents that are preserved will also be very different depending on type of slice. For example, in horizontal-oblique slices you can preserve both, corticostriatal and thalamostriatal afferents. Parasagittal slices are good if you want to study projections from prefrontal cortex. Of course, this is not as relevant if you only do intracellular stimulation.

Great points on age and slice configuration, Filipe.

Nice paper on patch and matrix and rostro-caudal variation, in coronal, sagital and horizontal sections. http://www.sciencedirect.com/science/article/pii/0306452293900136

Thank you for you suggestions. The references you provided are really interesting. Once I manage to do the compartment segregation during the recording I would update this post with my method.