Morphine differentially alters the synaptic and intrinsic properties of D1R- and D2R-expressing medium spiny neurons in the nucleus accumbens

Abstract

Exposure to opioids reshapes future reward and motivated behaviors partially by altering the functional output of medium spiny neurons (MSNs) in the nucleus accumbens shell. Here, we investigated how morphine, a highly addictive opioid, alters synaptic transmission and intrinsic excitability on dopamine D1-receptor (D1R) expressing and dopamine D2-receptor (D2R) expressing MSNs, the two main output neurons in the nucleus accumbens shell. Using wholecell electrophysiology recordings, we show, that 24 h abstinence following repeated noncontingent administration of morphine (10 mg/kg, i.p.) in mice reduces miniature excitatory postsynaptic current (mEPSC) frequency and miniature inhibitory postsynaptic current (mIPSC) frequency on D2R-MSNs, with concomitant increases in D2R-MSN intrinsic membrane excitability. We did not observe any changes on synaptic or intrinsic changes on D1R-MSNs. Lastly, in an attempt to determine the integrated effect of the synaptic and intrinsic alterations on the overall functional output of D2R-MSNs, we measured the input-output efficacy by measuring synaptically-driven action potential firing. We found that both D1R-MSN and D2R-MSN output was unchanged following morphine treatment. 42 4 much lesser degree (Bertran-Gonzalez et al., 2008). Mice were singly-housed and maintained on 43 a regular 12 hour light/dark cycle (lights on 07:00, lights off 19:00) with ad libitum food and 44 water. 45 2.2. Drugs 46 (−)-morphine sulfate pentahydrate was provided by the National Institute on Drug Abuse Drug 47 Supply Program. NBQX and AP5 were purchased from Tocris Biosciences. Picrotoxin was 48 purchased from Sigma Aldrich. Tetrodotoxin (TTX) was purchased from Enzo. 49 2.3. Repeated systemic injections of saline or morphine 50 Before drug administration, mice were allowed to acclimate to their home cages for >5d. For 51 drug treatment, we used a 5d repeated drug administration procedure (Huang et al., 52 2009;Graziane et al., 2016). In all electrophysiological experiments, once per d for 5d, mice were 53 taken out of the home cages for an intraperitoneal (i.p.) injection of either (−)-morphine sulfate 54 pentahydrate (10mg/kg in 0.9% saline) or the same volume of 0.9% saline, and then placed back 55 to the home cage at ~Zeitgeber time (ZT) 2 (ZT0=lights on, ZT12=lights off). Animals were 56 randomly selected for each drug treatment. Morphine-or saline-treated animals were then used 57 for electrophysiological recordings ~24h following the last injection.58 2.4. Acute Brain Slice Preparation 59 At ~ZT time 2, mice were deeply anesthetized with isoflurane and cardiac perfused with an ice-60 cold NMDG-based cutting solution containing (in mM): 135 N-methyl-d-glutamine, 1 KCl, 1.2 61 KH2PO4, 0.5 CaCl2, 1.5 MgCl2, 20 choline-HCO3, and 11 glucose, saturated with 62 95%O2/5%CO2, adjusted to a pH of 7.4 with HCl, osmolality adjusted to 305 mmol/kg. 63Following perfusion, mice were decapitated and brains were rapidly removed. 250 m coronal 64 brain slices containing the nucleus accumbens shell were prepared ...

Negative emotional behavior during fentanyl abstinence is mediated by adaptations in nucleus accumbens neuron subtypes

“…Both 1-and 10-14 day morphine abstinence reduce excitatory input onto D2-MSNs in the NAc shell (Graziane et al, 2016;Hearing et al, 2016;Madayag et al, 2019;McDevitt et al, 2019). In D1-MSNs, 1-day morphine abstinence has little impact on excitatory input (McDevitt et al, 2019), while 10-14 days increases GluA2 lacking AMPA receptors and excitatory drive on D1-MSNs specifically in the shell (Hearing et al, 2016;Madayag et al, 2019). Unlike the work of Hearing and colleagues, here we found adaptations in NAc core D1-MSNs.…”

“…Several recent studies have assessed how morphine abstinence alters excitatory transmission in specific NAc MSN subtypes. Both 1- and 10-14 day morphine abstinence reduce excitatory input onto D2-MSNs in the NAc shell (Graziane et al, 2016; Hearing et al, 2016; Madayag et al, 2019; McDevitt et al, 2019). In D1-MSNs, 1-day morphine abstinence has little impact on excitatory input (McDevitt et al, 2019), while 10-14 days increases GluA2 lacking AMPA receptors and excitatory drive on D1-MSNs specifically in the shell (Hearing et al, 2016; Madayag et al, 2019).…”

“…Opioid cessation also causes morphological and electrophysiological changes to NAc neurons. Most studies show decreased dendritic spine density and increased excitatory drive, however the physiologic responses are heterogenous, often NAc subregion specific, and in some cases there are no changes or a decrease in excitability dependent on the paradigm (Diana et al, 2006; Graziane et al, 2016; Hearing et al, 2016; Heng et al, 2008; Madayag et al, 2019; Matsubara et al, 1999; McDevitt et al, 2019; Pal and Das, 2013; Robinson and Kolb, 2004; Spiga et al, 2005; Thompson et al, 2021; Wu et al, 2012, 2013).…”

“…Increased activity in D1-MSNs is typically considered to be “pro-reward” and D2-MSNs “anti-reward,” however there are an increasing number of exceptions to this dichotomy in different parts of the striatum (Cui et al, 2013; Gallo et al, 2018; Gibson et al, 2018; Natsubori et al, 2017; Soares-Cunha et al, 2016, 2018, 2019; Vicente et al, 2016). Much less is known about specific MSN subtypes in opioid abstinence (Graziane et al, 2016; Hearing et al, 2016; Madayag et al, 2019; Martin et al, 2019; McDevitt et al, 2019), especially abstinence from synthetic opioids, and females were often excluded from previous studies. Further, many studies house animals singly, which is an added stressor that impacts drug-related behavior (Bozarth et al, 1989; Engeln et al, 2021; Kennedy et al, 2012; Westenbroek et al, 2013).…”

NPAS4 supports drug-cue associations and relapse-like behavior through regulation of the cell type-specific activation balance in the nucleus accumbens

“…Cocaine conditioning and/or shNPAS4 in D1-MSNs produced no significant changes in sEPSC frequency or amplitude (Figure S7C,E). Similar to prior literature on the effects of abused substances on D2-MSNs 20,56,70,71 , we observed that cocaine conditioning reduced sEPSC frequency (Figure S7D), but not amplitude (Figure S7F), in control D2-MSNs (black bars), and this reduction was abolished by shNPAS4 (Figure S7D). These data suggest that NPAS4 plays an important role in regulating drug-induced changes in excitatory synaptic transmission on D2-MSNs, but multiple glutamatergic inputs activate NAc MSNs and influence drug seeking 13,72,73 .…”