Same day discharge colon surgery: is it financially worth it?

AIM: Same day discharge (SDD) for colorectal surgery shows increasing promise in the era of enhanced recovery after surgery protocols and minimally invasive surgery. It has become increasingly relevant due to the constraints posed by the COVID-19 pandemic. The aim of this study was to compare SDD and postoperative day 1 (POD1) discharge to understand the clinical outcomes and financial impact on factors such as cost, charge, revenue, contribution margin and readmission. METHOD: A retrospective review of colectomies was performed at a single institution over a 2-year period (n = 143). Two populations were identified: SDD (n = 51) and POD1 (n = 92). Patients were selected by International Statistical Classification of Diseases and Related Health Problems-10 (ICD-10) and Diagnosis Related Grouper (DRG) codes. RESULTS: There was a statistically significant difference favouring SDD in total hospital cost (p < 0.0001), average direct costs (p < 0.0001) and average charges (p < 0.0016). SDD average hospital costs were $8699 (values in USD throughout) compared with $11 652 for POD 1 (p < 0.0001), and average SDD hospital charges were $85 506 compared with $97 008 for POD1 (p < 0.0016). The net revenue for SDD was $22 319 while for POD1 it was $26 173 (p = 0.14). Upon comparison of contribution margins (SDD $13 620 vs. POD1 $14 522), the difference was not statistically significant (p = 0.73). There were no identified statistically significant differences in operating room time, robotic console time, readmission rates or surgical complications. CONCLUSIONS: Amidst the pandemic-related constraints, we found that SDD was associated with lower hospital costs and comparable contribution margins compared with POD1. Additionally, the study was unable to identify any significant difference between operating time, readmissions, and surgical complications when performing SDD.

The patient perspective of same day discharge colectomy: one hundred patients surveyed on their experience following colon surgery.

INTRODUCTION: Guided by enhanced recovery after surgery protocols and coerced by constraints of the Coronavirus Disease 2019, the concept of same day discharge (SDD) after colon surgery is becoming a topic of great interest. Although only a few literature sources are published on the topic and protocols, the number of centers interested in SDD is increasing. With the small number of sources on protocol, safety, implementation, and criteria, there has yet to be a review of the patient experience and satisfaction. METHODS: Our institution has one of the largest American databases of SDD colon surgery. We performed a retrospective patient survey assessing perception of their surgical experience and satisfaction, which analyzed patients from February 2019 to January 2022. Fifty SDD patients were selected for participation, as well as fifty patients who were discharged on postoperative day 1 (POD1). An eleven-question survey was offered to patients and responses recorded. RESULTS: One hundred patients were contacted, 50 SDD and 50 POD1. Of the SDD patients, 41/50 (82%) patients participated in the survey, while 23/50 (46%) of POD1 patients participated. The highest average response in both populations was an understanding of patient postoperative mobility instructions (9.27/10, 9.68/10). The lowest average response in the SDD population was family comfort with discharge (8.17/10), while patient comfort with discharge was lowest in the POD1 group, (8.56/10). Importantly, we observed that 85.37% of patients who underwent SDD would do so again if given the opportunity. The only statistically significant variable was a difference in comfort with postoperative pain control, favoring the POD1 group, p = 0.02. CONCLUSIONS: SDD colon surgery is a feasible and reproducible option. Only comfort with postoperative pain control found a statistical difference, which we intend to improve upon with postanesthesia care unit education. Of patients reviewed who underwent SDD, most patients enjoyed their experience and would undergo SDD again.

Methodological considerations in region of interest definitions for paraspinal muscles in axial MRIs of the lumbar spine.

BACKGROUND: Magnetic Resonance Imaging (MRI) is commonly used to assess the health of the lumbar spine and supporting structures. Studies have suggested that fatty infiltration of the posterior lumbar muscles is important in predicting responses to treatment for low back pain. However, methodological differences exist in defining the region of interest (ROI) of a muscle, which limits the ability to compare data between studies. The purpose of this study was to determine reliability and systematic differences within and between two commonly utilized methodologies for ROI definitions of lumbar paraspinal muscle. METHODS: T2-weighted MRIs of the mid-L4 vertebrae from 37 patients with low back pain who were scheduled for lumbar spine surgery were included from a hospital database. Fatty infiltration for these patients ranged from low to high, based on Kjaer criteria. Two methods were used to define ROI: 1) segmentation of the multifidus and erector spinae based on fascial planes including epimuscular fat, and 2) segmentation of the multifidus and erector spinae based on visible muscle boundaries, which did not include epimuscular fat. Total cross sectional area (tCSA), fat signal fraction (FSF), muscle cross sectional area, and fat cross sectional area were measured. Degree of agreement between raters for each parameter was assessed using intra-class correlation coefficients (ICC) and area fraction of overlapping voxels. RESULTS: Excellent inter-rater agreement (ICC > 0.75) was observed for all measures for both methods. There was no significant difference between area fraction overlap of ROIs between methods. Method 1 demonstrated a greater tCSA for both the erector spinae (14-15%, p < 0.001) and multifidus (4%, p < 0.016) but a greater FSF only for the erector spinae (11-13%, p < 0.001). CONCLUSION: The two methods of defining lumbar spine muscle ROIs demonstrated excellent inter-rater reliability, although significant differences exist as method 1 showed larger CSA and FSF values compared to method 2. The results of this study confirm the validity of using either method to measure lumbar paraspinal musculature, and that method should be selected based on the primary outcome variables of interest.

Overexpression of ATF3 or the combination of ATF3, c-Jun, STAT3 and Smad1 promotes regeneration of the central axon branch of sensory neurons but without synergistic effects.

Peripheral nerve injury results in the activation of a number of transcription factors (TFs) in injured neurons, some of which may be key regulators of the regeneration-associated gene (RAG) programme. Among known RAG TFs, ATF3, Smad1, STAT3 and c-Jun have all been linked to successful axonal regeneration and have known functional and physical interactions. We hypothesised that TF expression would promote regeneration of the central axon branch of DRG neurons in the absence of a peripheral nerve lesion and that simultaneous overexpression of multiple RAG TFs would lead to greater effects than delivery of a single TF. Using adeno-associated viral vectors, we overexpressed either the combination of ATF3, Smad1, STAT3 and c-Jun with farnesylated GFP (fGFP), ATF3 only with fGFP, or fGFP only, in DRG neurons and assessed axonal regeneration after dorsal root transection or dorsal column injury and functional improvement after dorsal root injury. ATF3 alone and the combination of TFs promoted faster regeneration in the injured dorsal root. Surprisingly, however, the combination did not perform better than ATF3 alone. Neither treatment was able to induce functional improvement on sensory tests after dorsal root injury or promote regeneration in a dorsal column injury model. The lack of synergistic effects among these factors indicates that while they do increase the speed of axon growth, there may be functional redundancy between these TFs. Because axon growth is considerably less than that seen after a conditioning lesion, it appears these TFs do not induce the full regeneration programme.

The cost-effectiveness of dapagliflozin versus sulfonylurea as an add-on to metformin in the treatment of Type 2 diabetes mellitus.

AIMS: To assess the cost-effectiveness of dapagliflozin, a sodium-glucose co-transporter-2 (SGLT-2) inhibitor, compared with a sulfonylurea, when added to metformin for treatment of UK people with Type 2 diabetes mellitus inadequately controlled on metformin alone. METHODS: Clinical inputs sourced from a head-to-head randomized controlled trial (RCT) informed the Cardiff diabetes decision model. Risk equations developed from the United Kingdom Prospective Diabetes Study (UKPDS) were used in conjunction with the clinical inputs to predict disease progression and the incidence of micro- and macrovascular complications over a lifetime horizon. Cost and utility data were generated to present the incremental cost-effectiveness ratio (ICER) for both treatment arms, and sensitivity and scenario analyses were conducted to assess the impact of uncertainty on the final model results. RESULTS: The dapagliflozin treatment arm was associated with a mean incremental benefit of 0.467 quality-adjusted life years (QALYs) [95% confidence interval (CI): 0.420; 0.665], with an incremental cost of £1246 (95% CI: £613; £1637). This resulted in an ICER point estimate of £2671 per QALY gained. Incremental costs were shown to be insensitive to parameter variation, with only treatment-related weight change having a significant impact on the incremental QALYs. Probabilistic sensitivity analysis determined that dapagliflozin had a 100% probability of being cost-effective at a willingness-to-pay threshold of £20,000 per QALY. CONCLUSIONS: Dapagliflozin in combination with metformin was shown to be a cost-effective treatment option compared with sulfonylurea from a UK healthcare perspective for people with Type 2 diabetes mellitus who are inadequately controlled on metformin monotherapy.

Cost-effectiveness of dapagliflozin versus DPP-4 inhibitors as an add-on to Metformin in the Treatment of Type 2 Diabetes Mellitus from a UK Healthcare System Perspective.

BACKGROUND: Type 2 diabetes mellitus (T2DM) is a chronic, progressive condition where the primary treatment goal is to maintain control of glycated haemoglobin (HbA1c). In order for healthcare decision makers to ensure patients receive the highest standard of care within the available budget, the clinical benefits of each treatment option must be balanced against the economic consequences. The aim of this study was to assess the cost-effectiveness of dapagliflozin, the first-in-class sodium-glucose co-transporter 2 (SGLT2) inhibitor, compared with a dipeptidyl peptidase-4 inhibitor (DPP-4i), when added to metformin for the treatment of patients with T2DM inadequately controlled on metformin alone. METHODS: The previously published and validated Cardiff diabetes model was used as the basis for this economic evaluation, with treatment effect parameters sourced from a systematic review and network meta-analysis. Costs, derived from a UK healthcare system perspective, and quality-adjusted life years (QALYs), were used to present the final outcome as an incremental cost-effectiveness ratio (ICER) over a lifetime horizon. Univariate and probabilistic sensitivity analyses (PSA) were carried out to assess uncertainty in the model results. RESULTS: Compared with DPP-4i, dapagliflozin was associated with a mean incremental benefit of 0.032 QALYs (95% confidence interval [CI]: -0.022, 0.140) and with an incremental cost of £216 (95% CI: £-258, £795). This resulted in an ICER point estimate of £6,761 per QALY gained. Sensitivity analysis determined incremental costs to be insensitive to variation in most parameters, with only the treatment effect on weight having a notable impact on the incremental QALYs; however, there were no scenarios which raised the ICER above £15,000 per QALY. The PSA estimated that dapagliflozin had an 85% probability of being cost-effective at a willingness-to-pay threshold of £20,000 per QALY gained. CONCLUSIONS: Dapagliflozin in combination with metformin was shown to be a cost-effective treatment option from a UK healthcare system perspective for patients with T2DM who are inadequately controlled on metformin alone.

After a period of forced abstinence, rats treated with the norepinephrine neurotoxin DSP-4 still exhibit preserved food-seeking behavior and prefrontal cortex fos-expressing neurons.

Aims: Relapse is a common characteristic of compulsive behaviors like addiction, where individuals tend to return to drug use or overeating after a period of abstinence. PFC (prefrontal cortex) neuronal ensembles are required for drug and food-seeking behaviors and are partially regulated by Norepinephrine (NE). However, the contributions of neuromodulators, such as the adrenergic system, in food-seeking behavior are not fully understood. Main methods: To investigate this, we trained male and female rats to press a lever in an operant chamber to obtain banana-flavored food pellets for ten days. We then administered DSP-4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride), a neurotoxin that diminishes norepinephrine levels in the brain. The rats were kept in their home cages for ten more days before being returned to the operant chambers to measure food-seeking behavior. Key findings: Despite receiving DSP-4, the PFC neuronal ensembles measured by Fos and food-seeking behavior did not differ between groups, but rather sex. Significance: Although both NE and Fos expressing neurons are implicated in food-seeking, they do not seem to be involved in a cue-contextual induced re-exposure response.

Ambulatory colectomy: a pathway for advancing the enhanced recovery protocol.

Enhanced recovery after surgery (ERAS) protocols employ multiple factors to decrease surgical stress and improve recovery (Lyon et al., World J Gastroenterol 18(40):5661-5663, 2012). These protocols use multimodal approaches to improve outcomes, including length of stay and morbidities (Lyon et al., World J Gastroenterol 18(40):5661-5663, 2012; Carmichael et al., Dis Colon Rectum 60:761-784, 2017). The ERAS guidelines have evolved since development; however, the question is posed of how to improve next (Lyon et al., World J Gastroenterol 18(40):5661-5663, 2012). With the success of ERAS, in combination with milestones made by minimally invasive surgery (MIS), it is our aim to describe the next step of same day discharge colectomy. Retrospective review was performed on all colectomies from February 2019 to January 2022. Same day discharge (SDD) was defined as admission less than 23 h and no overnight stay. Procedures were nonemergent and MIS. Patients were candidates SDD based on comorbidities, communication means, and social support. SDD candidacy continued if surgery was uncomplicated. Next, patients were required to achieve strict Post Anesthesia Care Unit (PACU) criteria for discharge. SDD patients were monitored via calls or messages until their first appointment. After analysis, 326 total colectomies were identified; based on inclusion and exclusion criteria, 115 patients underwent SDD, 35.3%. Of the 115 SDD, 5 patients returned to the emergency department, only 1 required readmission (0.9%). The most performed procedures were low anterior resection, 61 (53.0%), and right hemicolectomy, 25 (21.7%). Using ERAS protocols as a groundwork to improve upon, we identified several ways to advance select patients into SDD. Using strict patient selection, intraoperative regulations, and rigorous postoperative criteria, we found that SDD as an advancement of ERAS is a relatively safe procedure with minimal complications.

Ambulatory colectomy: A pilot protocol for same day discharge in minimally invasive colorectal surgery.

BACKGROUND: Since its inception colectomy has routinely been performed in the inpatient setting. The advent of Enhanced Recovery After Surgery (ERAS) protocols has led improved outcomes, including decreased length of stay (LOS). These improvements have introduced the possibility of ambulatory colectomy. However, indications, protocols, and limitations of ambulatory colectomy have not been extensively explored. METHODS: We conducted a retrospective review on ambulatory colectomies performed between February 2019 and August 2021. Patients were candidates for same day discharge (SDD) if they met rigorous preoperative criteria. Following an uncomplicated operation, strict postoperative parameters were required for safe discharge. If the patient underwent SDD following their operation, they were monitored closely via telehealth visits and/or patient communication messages until their one-week postoperative visit. RESULTS: From our review, we identified sixty-nine (n = 69) patients who underwent SDD after colectomy. Of the 69, only one patient was readmitted after discharge (1.4%). All procedures were performed via a robotic-assisted approach (Da Vinci Xi). None of the patients underwent conversion to an open procedure. The most frequently performed procedures included: low anterior resection (LAR) (n = 32, 46.4%) and right hemicolectomy (n = 11, 15.9%). CONCLUSION: Through proper patient education and strictly defined communication between the patient care teams, safe and effective care in the setting of SDD after colectomy can be provided. With recent technological advancements, enhanced mechanisms for patient education throughout all phases, and emerging means of patient-physician communication, via the data included herein the opportunity for same day discharge (SDD) after colectomy is a feasible and safe management plan in the proper patient.

A novel, ataxic mouse model of ataxia telangiectasia caused by a clinically relevant nonsense mutation.

Ataxia Telangiectasia (A-T) and Ataxia with Ocular Apraxia Type 1 (AOA1) are devastating neurological disorders caused by null mutations in the genome stability genes, A-T mutated (ATM) and Aprataxin (APTX), respectively. Our mechanistic understanding and therapeutic repertoire for treating these disorders are severely lacking, in large part due to the failure of prior animal models with similar null mutations to recapitulate the characteristic loss of motor coordination (i.e., ataxia) and associated cerebellar defects. By increasing genotoxic stress through the insertion of null mutations in both the Atm (nonsense) and Aptx (knockout) genes in the same animal, we have generated a novel mouse model that for the first time develops a progressively severe ataxic phenotype associated with atrophy of the cerebellar molecular layer. We find biophysical properties of cerebellar Purkinje neurons (PNs) are significantly perturbed (e.g., reduced membrane capacitance, lower action potential [AP] thresholds, etc.), while properties of synaptic inputs remain largely unchanged. These perturbations significantly alter PN neural activity, including a progressive reduction in spontaneous AP firing frequency that correlates with both cerebellar atrophy and ataxia over the animal's first year of life. Double mutant mice also exhibit a high predisposition to developing cancer (thymomas) and immune abnormalities (impaired early thymocyte development and T-cell maturation), symptoms characteristic of A-T. Finally, by inserting a clinically relevant nonsense-type null mutation in Atm, we demonstrate that Small Molecule Read-Through (SMRT) compounds can restore ATM production, indicating their potential as a future A-T therapeutic.

Cyclical cervical function in the mare involves remodelling of collagen content, which is correlated with modification of oestrogen receptor 1 abundance.

This study was conducted to elucidate mare cervical dilation mechanisms by testing two hypotheses: (i) the proportion of collagen staining in histological samples of mare cervices and (ii) the abundance of hormone receptors in the equine cervix differ with stage of the oestrous cycle and site within the cervix. Tissues and jugular vein blood samples were collected from 15 mares. Collagen content was assessed using Masson's Trichome staining. Receptor abundance was assessed using RT-PCR, qRT-PCR and immunohistochemistry. In sub-epithelial stroma, there was less collagen during the follicular than luteal phase, in the caudal- (P =  0.029), mid- (P =  0.0000) and cranial (P =  0.001) cervical tissue. In the deep stroma, there was less collagen staining during the follicular stage in the mid- (P =  0.004) and cranial- (P =  0.041) cervical regions. There were PTGER2, PTGER3, PGR and ESR1 mRNA transcripts in the cervix. A greater proportion of cells were positive for ESR1 protein during the follicular phase in sub-epithelial (P =  0.019) and deep (P =  0.013) stroma. The abundance of ESR1 in the epithelium was negatively correlated with collagen staining in sub-epithelial (P =  0.007) and deep (P =  0.005) stroma. The results of the study provide new information about the cervical biology of mares by increasing the knowledge about collagen content and the relationship between collagen content and ESR1 protein abundance during the oestrous cycle which indicates the ESR1 receptor is a candidate for involvement in control of cervical dilation.

The Dorsal Column Lesion Model of Spinal Cord Injury and Its Use in Deciphering the Neuron-Intrinsic Injury Response.

The neuron-intrinsic response to axonal injury differs markedly between neurons of the peripheral and central nervous system. Following a peripheral lesion, a robust axonal growth program is initiated, whereas neurons of the central nervous system do not mount an effective regenerative response. Increasing the neuron-intrinsic regenerative response would therefore be one way to promote axonal regeneration in the injured central nervous system. The large-diameter sensory neurons located in the dorsal root ganglia are pseudo-unipolar neurons that project one axon branch into the spinal cord, and, via the dorsal column to the brain stem, and a peripheral process to the muscles and skin. Dorsal root ganglion neurons are ideally suited to study the neuron-intrinsic injury response because they exhibit a successful growth response following peripheral axotomy, while they fail to do so after a lesion of the central branch in the dorsal column. The dorsal column injury model allows the neuron-intrinsic regeneration response to be studied in the context of a spinal cord injury. Here we will discuss the advantages and disadvantages of this model. We describe the surgical methods used to implement a lesion of the ascending fibers, the anatomy of the sensory afferent pathways and anatomical, electrophysiological, and behavioral techniques to quantify regeneration and functional recovery. Subsequently we review the results of experimental interventions in the dorsal column lesion model, with an emphasis on the molecular mechanisms that govern the neuron-intrinsic injury response and manipulations of these after central axotomy. Finally, we highlight a number of recent advances that will have an impact on the design of future studies in this spinal cord injury model, including the continued development of adeno-associated viral vectors likely to improve the genetic manipulation of dorsal root ganglion neurons and the use of tissue clearing techniques enabling 3D reconstruction of regenerating axon tracts. © 2018 The Authors. Developmental Neurobiology Published by Wiley Periodicals, Inc. Develop Neurobiol 00: 000-000, 2018.

Small Scale Production of Recombinant Adeno-Associated Viral Vectors for Gene Delivery to the Nervous System.

Adeno-associated viral vectors have numerous applications in neuroscience, including the study of gene function in health and disease, targeting of light-sensitive proteins to anatomically distinct sets of neurons to manipulate neuronal activity (optogenetics), and the delivery of fluorescent protein to study anatomical connectivity in the brain. Moreover several phase I/II clinical trials for gene therapy of eye and brain diseases with adeno-associated viral vectors have shown that these vectors are well tolerated by human patients. In this chapter we describe a detailed protocol for the small scale production of recombinant adeno-associated viral vectors. This protocol can be executed by investigators with experience in cell culture and molecular biological techniques in any well-equipped molecular neurobiology laboratory. With this protocol we typically obtain research batches of 100-200 µL that range in titer from 5 × 1012 to 2 × 1013 genomic copies/mL.

Contribution of Lumbar Spine Pathology and Age to Paraspinal Muscle Size and Fatty Infiltration.

STUDY DESIGN: Retrospective chart analysis of 199 individuals aged 18 to 80 years scheduled for lumbar spine surgery. OBJECTIVE: The purpose of this study was to quantify changes in muscle cross-sectional area (CSA) and fat signal fraction (FSF) with age in men and women with lumbar spine pathology and compare them to published normative data. SUMMARY OF BACKGROUND DATA: Pathological changes in lumbar paraspinal muscle are often confounded by age-related decline in muscle size (CSA) and quality (fatty infiltration). Individuals with pathology have been shown to have decreased CSA and fatty infiltration of both the multifidus and erector spinae muscles, but the magnitude of these changes in the context of normal aging is unknown. METHODS: Individuals aged 18 to 80 years who were scheduled for lumbar surgery for diagnoses associated with lumbar spine pain or pathology were included. Muscle CSA and FSF of the multifidus and erector spinae were measured from preoperative T2-weighted magnetic resonance images at the L4 level. Univariate and multiple linear regression analyses were performed for each outcome using age and sex as predictor variables. Statistical comparisons of univariate regression parameters (slope and intercept) to published normative data were also performed. RESULTS: There was no change in CSA with age in either sex (P > 0.05), but women had lower CSAs than men in both muscles (P < 0.0001). There was an increase in FSF with age in erector spinae and multifidus muscles in both sexes (P < 0.0001). Multifidus FSF values were higher in women with lumbar spine pathology than published values for healthy controls (P = 0.03), and slopes tended to be steeper with pathology for both muscles in women (P < 0.08) but not in men (P > 0.31). CONCLUSION: Lumbar muscle fat content, but not CSA, changes with age in individuals with pathology. In women, this increase is more profound than age-related increases in healthy individuals. LEVEL OF EVIDENCE: 3.

Evaluation of Five Tests for Sensitivity to Functional Deficits following Cervical or Thoracic Dorsal Column Transection in the Rat.

The dorsal column lesion model of spinal cord injury targets sensory fibres which originate from the dorsal root ganglia and ascend in the dorsal funiculus. It has the advantages that fibres can be specifically traced from the sciatic nerve, verifiably complete lesions can be performed of the labelled fibres, and it can be used to study sprouting in the central nervous system from the conditioning lesion effect. However, functional deficits from this type of lesion are mild, making assessment of experimental treatment-induced functional recovery difficult. Here, five functional tests were compared for their sensitivity to functional deficits, and hence their suitability to reliably measure recovery of function after dorsal column injury. We assessed the tape removal test, the rope crossing test, CatWalk gait analysis, and the horizontal ladder, and introduce a new test, the inclined rolling ladder. Animals with dorsal column injuries at C4 or T7 level were compared to sham-operated animals for a duration of eight weeks. As well as comparing groups at individual timepoints we also compared the longitudinal data over the whole time course with linear mixed models (LMMs), and for tests where steps are scored as success/error, using generalized LMMs for binomial data. Although, generally, function recovered to sham levels within 2-6 weeks, in most tests we were able to detect significant deficits with whole time-course comparisons. On the horizontal ladder deficits were detected until 5-6 weeks. With the new inclined rolling ladder functional deficits were somewhat more consistent over the testing period and appeared to last for 6-7 weeks. Of the CatWalk parameters base of support was sensitive to cervical and thoracic lesions while hind-paw print-width was affected by cervical lesion only. The inclined rolling ladder test in combination with the horizontal ladder and the CatWalk may prove useful to monitor functional recovery after experimental treatment in this lesion model.

Increased extracellular glutamate in the nucleus accumbens promotes excessive ethanol drinking in ethanol dependent mice.

Using a well-established model of ethanol dependence and relapse, this study examined adaptations in glutamatergic transmission in the nucleus accumbens (NAc) and their role in regulating voluntary ethanol drinking. Mice were first trained to drink ethanol in a free-choice, limited access (2 h/day) paradigm. One group (EtOH mice) received repeated weekly cycles of chronic intermittent ethanol (CIE) exposure with intervening weeks of test drinking sessions, whereas the remaining mice (CTL mice) were similarly treated but did not receive CIE treatment. Over repeated cycles of CIE exposure, EtOH mice exhibited significant escalation in drinking (up to ∼3.5 g/kg), whereas drinking remained relatively stable at baseline levels (2-2.5 g/kg) in CTL mice. Using in vivo microdialysis procedures, extracellular glutamate (GLUEX) levels in the NAc were increased approximately twofold in EtOH mice compared with CTL mice, and this difference was observed 7 days after final CIE exposure, indicating that this hyperglutamatergic state persisted beyond acute withdrawal. This finding prompted additional studies examining the effects of pharmacologically manipulating GLUEX in the NAc on ethanol drinking in the CIE model. The non-selective glutamate reuptake antagonist, threo-ß-benzyloxyaspartate (TBOA), was bilaterally microinjected into the NAc and found to dose-dependently increase drinking in nondependent (CTL) mice to levels attained by dependent (EtOH) mice. TBOA also further increased drinking in EtOH mice. In contrast, reducing glutamatergic transmission in the NAc via bilateral injections of the metabotropic glutamate receptor-2/3 agonist LY379268 reduced drinking in dependent (EtOH) mice to nondependent (CTL) levels, whereas having a more modest effect in decreasing ethanol consumption in CTL mice. Taken together, these data support an important role of glutamatergic transmission in the NAc in regulating ethanol drinking. Additionally, these results indicate that ethanol dependence produces adaptations that favor elevated glutamate activity in the NAc which, in turn, promote excessive levels of ethanol consumption associated with dependence.