Lab Update / Covid 19

Its been a while since I updated the lab blog and things have been a bit hectic amidst the Covid 19 global pandemic. I certainly wish everyone the best in these strange times. Hopefully, everyone is staying safe and healthy. As expected, conferences and talks have not been held in person and zoom meetings reign supreme. So no exciting updates in that department.

In the lab, we are continuing on as best we can, being careful to keep our masks on and maintain appropriate social distancing while conducting our studies.

Below I have posted some random older MUSC and lab-related images. These are pre-pandemic so please forgive the lack of masks.

SFN 2018 - San Diego

The Scofield Lab (Drs Scofield and Siemsen) experienced this SFN meeting in San Diego to the fullest!. We presented both a conventional, and a dynamic poster at the annual meeting for the Society of Neuroscience and caught up with members of previous laboratories and those that have moved on to start their own labs. This years meeting was particularly fantastic due to the great weather and people in San Diego. We also enjoyed the fantastic food, especially the fruits and vegetables. with a particular focus on all things Acai. Our favorite spot was a small place very close to our lodging called ‘Cafe by the Bay’ that had amazing Acai sorbet bowls. Additionally, we spent a good deal of time in the evening exploring a suburb of San Diego, Pacific beach, on electric scooters. Remarkably, only relatively minor injuries resulted.

In summary, it was especially unique to have our lab selected for a dynamic poster, as this improved the visibility of our work and gave Dr. Siemsen a bit more exposure than one usually gets with a conventional poster. Dr Scofield also spoke with several researches keen on using confocal microscopy to investigate morphometric features of non-neuronal cells.

We had a great meeting and look forward to seeing everyone again soon.

Astrocytes and Addiction

During my postdoctoral training at MUSC I began to investigate the use of viral vector mediated astrocyte-specific expression of DREADD receptors. In these studies I used glutamate biosensor recordings to determine if activation of NAcore astrocytes produced detectable glutamate release. Following cocaine self-administration and extinction, I found that activation of glial DREADD receptors, and subsequent inhibited cue-induced cocaine seeking, in part by restoring tone on presynaptic mGluR2/3 autoreceptors (study a.). Becoming more interested in astrocytes, I began to implement the use another glial cell-specific viral vector (GFAP-LCK-GFP) designed to restrict expression of GFP to the astrocyte plasma membrane. Using this viral vector, I labeled, imaged, and digitally reconstructed NAcore astrocytes to examine their morphological characteristics following cocaine self-admin and extinction. These studies demonstrated reduced volume and surface area of astrocytes following cocaine self-administration and extinction. By combining the astrocyte viral signal with fluorescent detection of a synaptic marker, I also observed decreased contact of NAcore astrocytes with a synaptic marker, which paralleled decreases in surface area and volume and previously reported decreases in glutamate clearance. Interestingly, decreased synaptic contact was reversed with ceftriaxone treatment, a drug that restores cocaine-induced alterations in glutamate homeostasis by enhancing expression of glial proteins responsible for uptake and release of glutamate (study b.). While setting up my laboratory at MUSC in the department of Anesthesiology I have continued to explore the microscopic investigation of astrocytes and their interaction with neurons, compiling some additional optogenetics-based glutamate biosensor data with super-resolution images of the astrocyte plasma membrane and corresponding glial fibrillary acid protein arbor in a recent publication where I compile recent results from the field with the conclusions made from my earlier astrocyte work (study c.).  These studies are ongoing in the laboratory and we have begun to develop a series of new assays and techniques that take advantage of our new super resolution microscope.

a.     Scofield MD, Boger HA, Smith RJ, Li H, Haydon PG and Kalivas PW (2015). Gq-DREADD Selectively Initiates Glial Glutamate Release and Inhibits Cue-induced Cocaine Seeking. Biol Psychiatry 78:441-451 (PMC4547911)

b.     Scofield MD, Li H, Siemsen B, Healy KL, Tran PK, Woronoff N, Boger HA, Kalivas PW and Reissner KJ. (2016) Cocaine self-administration and extinction leads to reduced GFAP expression and morphometric features of astrocytes in the nucleus accumbens core. Biol Psychiatry 80:207-215 (PMC4930433)

c.     Scofield MD. (2017). Exploring the role of astroglial glutamate release and association with synapses in neuronal function and behavior. Biol Psychiatry [Epub Ahead of Print] (PMC5948108)

Nitric Oxide and Relapse

Relapse is a defining feature of drug addiction, and despite years of research we still lack adequate treatments for this disease. Using the rodent self-administration and reinstatement model, we can study how drug exposure sets the stage for relapse vulnerability. I have used glutamate-selective biosensors to investigate the rate of glutamate uptake in animals following heroin self-administration and extinction training, and detected decreased clearance in the NAcore. I was also involved with another project where we began to closely analyze the signal transduction cascade underlying increases in dendritic spine head diameter (dh) responsible for relapse to cued cocaine seeking. We observed in these studies that activity of matrix metalloproteinases 2 and 9 are required for cued cocaine seeking (study b.) In the latest study in this line of investigation, we demonstrated that a key component in the signal transduction cascade leading to the activation of MMPs in the NAcore is the release of NO. We showed that activation of NAcore NO interneurons was sufficient to drive drug seeking even in the absence of conditioned cues, while the selective destruction of these cells inhibited drug seeking. We are currently performing recordings in freely moving animals to further analyze the relationship between glutamate and NO in drug seeking and taking.

a.    Shen HW, Scofield MD, Boger H, Hensley M and Kalivas PW (2014) Synaptic glutamate spillover due to impaired glutamate uptake mediates heroin relapse. J Neurosci 34:5649-5657 (PMC3988415)

b.     Smith AC, Kupchik YM, Scofield MD, Gipson CD, Wiggins A, Thomas CA and Kalivas PW (2014) Synaptic plasticity mediating cocaine relapse requires matrix metalloproteinases. Nat Neurosci 17:1655-1657 (PMC4241163)

c.     Smith AC, Scofield MD, Heinsbroek JA, Gipson CD, Neuhofer D, Roberts-Wolfe DJ, Spencer S, Garcia-Keller C, Stankeviciute NM, Smith RJ, Allen NP, Lorang MR, Griffin WC 3rd, Boger HA, and Kalivas PW (2017) Accumbens nNOS interneurons regulate cocaine relapse. J. Neurosci 37(4):742-756 (PMC5296777)