Severe drug-induced repetitive behaviors and striatal overexpression of VAChT in ChAT-ChR2-EYFP BAC transgenic mice

Abstract

In drug users, drug-related cues alone can induce dopamine release in the dorsal striatum. Instructive cues activate inputs to the striatum from both dopaminergic and cholinergic neurons, which are thought to work together to support motor learning and motivated behaviors. Imbalances in these neuromodulatory influences can impair normal action selection and might thus contribute to pathologically repetitive and compulsive behaviors such as drug addiction. Dopamine and acetylcholine can have either antagonistic or synergistic effects on behavior, depending on the state of the animal and the receptor signaling systems at play. Semi-synchronized activation of cholinergic interneurons in the dorsal striatum drives dopamine release via presynaptic nicotinic acetylcholine receptors located on dopamine terminals. Nicotinic receptor blockade is known to diminish abnormal repetitive behaviors (stereotypies) induced by psychomotor stimulants. By contrast, blockade of postsynaptic acetylcholine muscarinic receptors in the dorsomedial striatum exacerbates drug-induced stereotypy, exemplifying how different acetylcholine receptors can also have opposing effects. Although acetylcholine release is known to be altered in animal models of drug addiction, predicting whether these changes will augment or diminish drug-induced behaviors thus remains a challenge. Here, we measured amphetamine-induced stereotypy in BAC transgenic mice that have been shown to overexpress the vesicular acetylcholine transporter (VAChT) with consequent increased acetylcholine release. We found that drug-induced stereotypies, consisting of confined sniffing and licking behaviors, were greatly increased in the transgenic mice relative to sibling controls, as was striatal VAChT protein. These findings suggest that VAChT-mediated increases in acetylcholine could be critical in exacerbating drug-induced stereotypic behaviors and promoting exaggerated behavioral fixity.

Compartmental function and modulation of the striatum

“…Specifically, using CalDAG-GEFI-EGFP mice to visualize matrix neurons, Crittenden and colleagues demonstrated that optogenetic stimulation of CINs disrupts the firing patterns of SPNs in ex vivo striatal slices in a nAChR-dependent way, although the dependence upon GABA remains unclear. This, along with observations that (a) destruction of striatal CINs (and somatostatinergic interneurons) prevents the above drug-induced striosome/matrix pattern of cFos induction, (b) pharmacological blockade of striatal cholinergic signaling increases drug-induced stereotypies, and (c) globally elevating acetylcholine release also exacerbates drug-induced stereotypies(Aliane, Perez, Bohren, Deniau, & Kemel, 2011;Crittenden et al, 2014;Janickova, Prado, Prado, El Mestikawy, & Bernard, 2017;Saka, Iadarola, Fitzgerald, & Graybiel, 2002; see also the preprint byCrittenden et al, deposited in bioRxiv on July 22, 2019 https ://www.biorx iv.org/conte nt/10.1101/709246v1), suggests that a precise balance of striatal cholinergic signaling may be required to shape striosome-linked behaviors and prevent pathological stereotypy. This, along with observations that (a) destruction of striatal CINs (and somatostatinergic interneurons) prevents the above drug-induced striosome/matrix pattern of cFos induction, (b) pharmacological blockade of striatal cholinergic signaling increases drug-induced stereotypies, and (c) globally elevating acetylcholine release also exacerbates drug-induced stereotypies(Aliane, Perez, Bohren, Deniau, & Kemel, 2011;Crittenden et al, 2014;Janickova, Prado, Prado, El Mestikawy, & Bernard, 2017;Saka, Iadarola, Fitzgerald, & Graybiel, 2002; see also the preprint byCrittenden et al, deposited in bioRxiv on July 22, 2019 https ://www.biorx iv.org/conte nt/10.1101/709246v1), suggests that a precise balance of striatal cholinergic signaling may be required to shape striosome-linked behaviors and prevent pathological stereotypy.…”

Transgenic labeling of parvalbumin-expressing neurons with tdTomato

“…In addition, we used a BAC-trimming approach to remove a nearby gene in the BAC clone to avoid undesirable overexpression of this gene (Ting and Feng, 2014). This is an important step that has not been carried out in previously generated BAC transgenic mice and has resulted in lines with potential confounding and unintended overexpression of unwanted genes (Kolisnyk et al, 2013, Crittenden et al, 2014). …”

Striosome–dendron bouquets highlight a unique striatonigral circuit targeting dopamine-containing neurons

“…Much evidence suggests that cholinergic interneurons in the striatum can exert powerful control over the intrastriatal release of dopamine (34,35). We have noted that these cholinergic interneurons, although having predominant distributions at the striosome-matrix compartment borders (36), send many fine fibers into the striosomes (37,38). By contrast, cholinergic inputs from the brainstem pedunculopontine nucleus (PPN) preferentially innervate the matrix (39).…”