Methods and protocols for translatable rodent models of postsurgical pain.

Due to the large volume of surgeries and the subsequent incidence of postsurgical pain, it is vital that the underlying mechanisms of postsurgical pain are thoroughly understood. The intensity of acute postsurgical pain is typically dependent on the severity of tissue damage the surgery produces, and the development of chronic pain is more frequent in major surgeries than in minor ones. It is therefore important that postsurgical pain studies are conducted with the differences between major and minor surgeries in mind. To this end, the paw incision and skin muscle incision and retraction models are the focus of this chapter as they feature aspects observed in minor and major surgeries in humans, respectively. Several elements of these models translate to humans with some limitations, as they allow for the measurement of reflexive, spontaneous, and functional pain-like behavior. For these attributes, the SMIR and paw incision surgeries are widely used in postsurgical pain research. Here we layout detailed protocols to instruct experienced as well as inexperienced researchers studying postsurgical pain in rats and mice.

Methods and protocols for chemotherapy-induced peripheral neuropathy (CIPN) mouse models using paclitaxel.

While cancer patients may have chemotherapeutics to thank for being cured of their malignancy, they are often left to suffer a disabling neuropathy induced by that same cancer treatment. This neuropathy, known as chemotherapy-induced peripheral neuropathy, or CIPN, is one of the most debilitating survivorship concerns for patients, with many citing hallmark symptoms of hyperalgesia, allodynia, and numbness, and subsequently reducing their dose or even ceasing treatment altogether. Investigations into this interplay between the antineoplastic activity of chemotherapeutic agents and the preservation of peripheral nerve health are therefore crucial for the development of CIPN treatment and prevention methods. Responding to need, current literature is inundated with varying preclinical models of CIPN. This chapter thus seeks to provide a detailed and reliable methodology for the induction and assessment of CIPN in mice, using a preclinical model that is both reproducible and translatable to several aspects of the clinical phenotype. Specifically, this chapter lays out a model for intermittent low-dose paclitaxel induction of CIPN in C57BL/6J mice, and a testing of this induction via von Frey filament mechanical hypersensitivity assays, a mechanical hyposensitivity (numbness) assay, and a cold-thermal allodynia assay (acetone test). These protocols can easily be adjusted to fit the needs of individual CIPN experiments, as stated throughout the chapter.

Chronic Ethanol Exposures Leads to a Negative Affective State in Female Rats That Is Accompanied by a Paradoxical Decrease in Ventral Hippocampus Excitability.

Alcohol use disorder (AUD) differentially impacts men and women and a growing body of evidence points to sex-dependent adaptations in a number of brain regions. In a prior study, we explored the effect of a chronic intermittent ethanol exposure (CIE) model of AUD on neuronal and molecular adaptations in the dorsal and ventral domains of the hippocampus (dHC and vHC, respectively) in male rats. We found the vHC to be particularly sensitive to CIE, showing an increase in neuronal excitability and synaptic proteins associated with augmented excitation. These findings were accompanied by a CIE-dependent increase in anxiety-like behaviors. To explore sex-dependent adaptations in the hippocampus, we conducted a similar study in female rats. CIE-treated female rats showed a relatively modest increase in anxiety-like behaviors along with a robust increase in depressive-like measures. Despite both sexes showing clear evidence of a negative affective state following CIE, the vHC of females showed a decrease, rather than an increase, in neuronal excitability. In line with the reduced sensitivity to neural adaptations in the dHC of male rats, we were unable to identify any functional changes in the dHC of females. The functional changes of the vHC in female rats could not be explained by altered expression levels of a number of proteins typically associated with changes in neuronal excitability. Taken together, these findings point to sex as a major factor in CIE-dependent hippocampal adaptations that should be explored further to better understand possible gender differences in the etiology and treatment of AUD.

Buspirone for functional improvement after acute traumatic spinal cord injury: a propensity score-matched cohort study.

STUDY DESIGN: Retrospective analysis of treated inpatients compared to expected neurorecovery from a propensity score-matched national database cohort. OBJECTIVE: Evaluate the effectiveness of buspirone on clinical neurorecovery following traumatic SCI when started during acute inpatient rehabilitation. SETTING: University-based hospital in Boston, USA. METHODS: Chart review yielded thirty-one individuals with acute, traumatic SCI treated with buspirone during inpatient rehabilitation from 2011-2017. Propensity score matching to a cohort of individuals from the spinal cord injury model systems (SCIMS) national database was completed. Changes in upper extremity motor score (UEMS), lower extremity motor score (LEMS), American Spinal Injury Association Impairment Scale (AIS), neurological level of injury (NLI), and functional impairment measure (FIM) from admission to discharge and discharge to 1 year were computed and compared between matched pairs (buspirone and mean national SCIMs cohort). A local control cohort not treated with buspirone was similarly compared to a matched mean national SCIMs group to identify location-specific effects. RESULTS: From admission to discharge from inpatient rehabilitation, 95% confidence intervals of changes in UEMS (-2.43 to +2.78), LEMS (-1.02 to +6.02), AIS (-0.04 to +0.35), NLI (-0.42 to +1.08), and FIM (-4.42 to +6.40) were not significantly different between those individuals who received buspirone and their propensity-matched SCIMS cohort. Similarly, changes in these metrics were not significantly different at 1-year follow up. Buspirone group individuals with initial clinically complete SCI demonstrated a higher 1-year conversion rate to incomplete injury (6 out of 14; 42.9%) compared to the matched national SCIMS cohort (14 out of 70; 21.2%, p = 0.047) though this was not significantly different from non-buspirone local controls (p = 0.25). CONCLUSIONS: Retrospective analysis shows no statistically significant difference in gross markers of neurorecovery following acute traumatic SCI when buspirone is initiated indiscriminately during acute inpatient rehabilitation. In individuals with clinically complete SCI, findings suggest possible increased rates of 1-year conversion to incomplete injury.

Functional status predicts acute care readmission in the traumatic spinal cord injury population.

CONTEXT/OBJECTIVE: Acute care readmission has been identified as an important marker of healthcare quality. Most previous models assessing risk prediction of readmission incorporate variables for medical comorbidity. We hypothesized that functional status is a more robust predictor of readmission in the spinal cord injury population than medical comorbidities. DESIGN: Retrospective cross-sectional analysis. SETTING: Inpatient rehabilitation facilities, Uniform Data System for Medical Rehabilitation data from 2002 to 2012. PARTICIPANTS: traumatic spinal cord injury patients. OUTCOME MEASURES: A logistic regression model for predicting acute care readmission based on demographic variables and functional status (Functional Model) was compared with models incorporating demographics, functional status, and medical comorbidities (Functional-Plus) or models including demographics and medical comorbidities (Demographic-Comorbidity). The primary outcomes were 3- and 30-day readmission, and the primary measure of model performance was the c-statistic. RESULTS: There were a total of 68,395 patients with 1,469 (2.15%) readmitted at 3 days and 7,081 (10.35%) readmitted at 30 days. The c-statistics for the Functional Model were 0.703 and 0.654 for 3 and 30 days. The Functional Model outperformed Demographic-Comorbidity models at 3 days (c-statistic difference: 0.066-0.096) and outperformed two of the three Demographic-Comorbidity models at 30 days (c-statistic difference: 0.029-0.056). The Functional-Plus models exhibited negligible improvements (0.002-0.010) in model performance compared to the Functional models. CONCLUSION: Readmissions are used as a marker of hospital performance. Function-based readmission models in the spinal cord injury population outperform models incorporating medical comorbidities. Readmission risk models for this population would benefit from the inclusion of functional status.

Chronic Intermittent Ethanol Exposure Selectively Increases Synaptic Excitability in the Ventral Domain of the Rat Hippocampus.

Many studies have implicated hippocampal dysregulation in the pathophysiology of alcohol use disorder (AUD). However, over the past twenty years, a growing body of evidence has revealed distinct functional roles of the dorsal (dHC) and ventral (vHC) hippocampal subregions, with the dHC being primarily involved in spatial learning and memory and the vHC regulating anxiety- and depressive-like behaviors. Notably, to our knowledge, no rodent studies have examined the effects of chronic ethanol exposure on synaptic transmission along the dorsal/ventral axis. To that end, we examined the effects of the chronic intermittent ethanol vapor exposure (CIE) model of AUD on dHC and vHC synaptic excitability. Adult male Long-Evans rats were exposed to CIE or AIR for 10 days (12 h/day; targeting blood ethanol levels of 175-225 mg%) and recordings were made 24 h into withdrawal. As expected, this protocol increased anxiety-like behaviors on the elevated plus-maze and successive alleys test. Extracellular recordings revealed marked CIE-associated increases in synaptic excitation in the CA1 region that were exclusively restricted to the ventral domain of the hippocampus. Western blot analysis of synaptoneurosomal fractions revealed that the expression of two proteins that regulate synaptic strength, GluA2 and SK2, were dysregulated in the vHC, but not the dHC, following CIE. Together, these findings suggest that the ventral CA1 region may be particularly sensitive to the maladaptive effects of chronic ethanol exposure and provide new insight into some of the neural substrates that may contribute to the negative affective state that develops during withdrawal.

Proteasome limits plasticity-related signaling to the nucleus in the hippocampus.

Proteolysis by the ubiquitin-proteasome pathway has pleiotropic effects on both induction and maintenance of long-term synaptic plasticity. In this study, we examined the effect of proteasome inhibition on signaling to the nucleus during late-phase long-term potentiation. When a subthreshold L-LTP induction protocol was used, proteasome inhibition led to a significant increase in phosphorylated CREB (pCREB) in the nucleus. Inhibitors of cAMP-dependent protein kinase/protein kinase A, extracellular signal-regulated kinase and cGMP-dependent protein kinase/protein kinase G all blocked the proteasome-inhibition-mediated increase in nuclear pCREB after subthreshold stimulation. These results lay the groundwork for understanding a novel role for the proteasome in limiting signaling to the nucleus in the absence of adequate synaptic stimulation.

Augmenting exercise capacity with noninvasive ventilation in high-level spinal cord injury.

High-level spinal cord injury (SCI) results in a very limited innervated skeletal muscle mass that strongly reduces exercise capacity. Our recent work showed that when adding functional electrical stimulation (FES) of the paralyzed legs (hybrid FES-exercise) to produce higher exercise capacity, peak ventilation became a limiting factor to training-induced improvement in aerobic capacity. Our assumption was that the systemic adaptations to exercise training are delimited by the maximal ventilation that can be achieved. However, herein, we present a case showing an acute increase in aerobic capacity when using noninvasive ventilatory support (NIV) during FES-rowing test in an individual who had previously experimented a plateau in his aerobic capacity for 18 mo. An 18-yr-old man with C5 SCI trained with arms-only rowing for 6 mo and subsequently trained with hybrid FES-rowing for 18 mo. Peak minute ventilation (V̇epeak) and peak oxygen consumption (V̇o2peak) were increased after arms-only training and increased further with 6 mo of hybrid FES-row training. Despite continued intense and frequent, hybrid FES-row training, neither V̇epeak nor V̇o2peak increased further over the next year (1.94 and 66.0 l/min). However, when this individual performed a FES-rowing V̇o2peak test with the addition of NIV, V̇epeak increased by 5 l/min, resulting in an improved V̇o2peak (2.23 l/min, +12%). This case demonstrates that noninvasive ventilation can overcome limitations to ventilation in high-level SCI and improve aerobic capacity during hybrid FES-exercise to a level not otherwise achievable. In addition, it broadly illustrates the intimate role of pulmonary function in determining the capacity to perform exercise.

Enhanced ventral hippocampal synaptic transmission and impaired synaptic plasticity in a rodent model of alcohol addiction vulnerability.

It has long been appreciated that adolescence represents a uniquely vulnerable period when chronic exposure to stressors can precipitate the onset of a broad spectrum of psychiatric disorders and addiction in adulthood. However, the neurobiological substrates and the full repertoire of adaptations within these substrates making adolescence a particularly susceptible developmental stage are not well understood. Prior work has demonstrated that a rodent model of adolescent social isolation (aSI) produces robust and persistent increases in phenotypes relevant to anxiety/stressor disorders and alcohol addiction, including anxiogenesis, deficits in fear extinction, and increased ethanol consumption. Here, we used extracellular field recordings in hippocampal slices to investigate adaptations in synaptic function and synaptic plasticity arising from aSI. We demonstrate that this early life stressor leads to enhanced excitatory synaptic transmission and decreased levels of long-term potentiation at hippocampal Schaffer collateral-CA1 synapses. Further, these changes were largely confined to the ventral hippocampus. As the ventral hippocampus is integral to neurocircuitry that mediates emotional behaviors, our results add to mounting evidence that aSI has profound effects on brain areas that regulate affective states. These studies also lend additional support to our recent proposal of the aSI model as a valid model of alcohol addiction vulnerability.

Proteasome regulates transcription-favoring histone methylation, acetylation and ubiquitination in long-term synaptic plasticity.

Histone modifications, such as lysine methylation, acetylation and ubiquitination, are epigenetic tags that shape the chromatin landscape and regulate transcription required for synaptic plasticity and memory. Here, we show that transcription-promoting histone H3 trimethylated at lysine 4 (H3K4me3), histone H3 acetylated at lysine 9 and 14 (H3K9/14ac), and histone H2B monoubiquitinated at lysine 120 (H2BK120ub) are enhanced after the induction of long-lasting chemically-induced long-term potentiation (cLTP) in the murine hippocampus. While H3K4me3 and H3K9/14ac were transiently upregulated, H2BK120ub levels oscillated after cLTP induction. In addition, we present results showing that blocking the proteasome, a molecular complex specialized for targeted protein degradation, inhibited the upregulation of these epigenetic tags after cLTP. Thus, our study provides the initial steps toward understanding the role of the proteasome in regulating histone modifications critical for synaptic plasticity.