Background-Exercise has recently been suggested as an attractive alternative to pharmacotherapy for treating drug addiction. The goal of the current study was to determine using an animal model whether aerobic exercise may block reinstatement of cocaine-seeking and its underlying neurobiology (i.e., neuronal signaling in the prefrontal cortex).

A recent clinical study demonstrated that damage to the insular cortex can disrupt tobacco addiction. The neurobiological mechanisms for this effect are not yet understood. In this study we used an animal model of nicotine addiction to examine the possibility that changes in insular cortex levels of dopamine (DA)- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32), a phosphoprotein enriched in DA neurons containing DA D1 receptors, may be associated with changes in vulnerability to nicotine addiction. Once rats acquired self-administration, they were given unlimited access to nicotine (0.01 mg/kg/infusion) for 23 h/day for a total of 10 days. Each infusion was paired with a visual cue (stimulus light) and auditory cue (sound of pump). Nicotine seeking, as assessed under a cue-induced reinstatement paradigm, and markers of DARPP-32 signaling, as assessed using western blot analysis, were examined in separate groups of rats at two different abstinent intervals: 1 and 7 days. Consistent with findings with other drugs of abuse, rats in the 7-day abstinence group took longer to extinguish and responded at higher levels during reinstatement testing as compared with rats in the 1-day reinstatement group. Relative to saline controls, rats in the 7-day but not the 1-day abstinence group had higher levels of DARPP-32 phosphorylated at the protein kinase A site in the insular cortex. These results demonstrate incubation of drug seeking following extended access to nicotine self-administration and suggest that enhanced protein kinase A signaling in the insular cortex via phosphorylation of DARPP-32 at Thr34 is associated with this effect.

Traumatic brain injury is among the most common causes of death and disability in youth and young adults. In addition to the acute risk of morbidity with moderate to severe injuries, traumatic brain injury is associated with a number of chronic neurological and neuropsychiatric sequelae including neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease. However, despite the high incidence of traumatic brain injuries and the established clinical correlation with neurodegeneration, the causative factors linking these processes have not yet been fully elucidated. Apart from removal from activity, few, if any prophylactic treatments against post-traumatic brain injury neurodegeneration exist. Therefore, it is imperative to understand the pathophysiological mechanisms of traumatic brain injury and neurodegeneration in order to identify potential factors that initiate neurodegenerative processes. Oxidative stress, neuroinflammation, and glutamatergic excitotoxicity have previously been implicated in both secondary brain injury and neurodegeneration. In particular, reactive oxygen species appear to be key in mediating molecular insult in neuroinflammation and excitotoxicity. As such, it is likely that post injury oxidative stress is a key mechanism which links traumatic brain injury to increased risk of neurodegeneration. Consequently, reactive oxygen species and their subsequent byproducts may serve as novel fluid markers for identification and monitoring of cellular damage. Furthermore, these reactive species may further serve as a suitable therapeutic target to reduce the risk of post-injury neurodegeneration and provide long term quality of life improvements for those suffering from traumatic brain injury.

OBJECTIVE Blast-induced neurotrauma (BINT), if not fatal, is nonetheless potentially crippling. It can produce a wide array of acute symptoms in moderate-to-severe exposures, but mild BINT (mBINT) is characterized by the distinct absence of acute clinical abnormalities. The lack of observable indications for mBINT is particularly alarming, as these injuries have been linked to severe long-term psychiatric and degenerative neurological dysfunction. Although the long-term sequelae of BINT are extensively documented, the underlying mechanisms of injury remain poorly understood, impeding the development of diagnostic and treatment strategies. The primary goal of this research was to recapitulate primary mBINT in rodents in order to facilitate well-controlled, long-term investigations of blast-induced pathological neurological sequelae and identify potential mechanisms by which ongoing damage may occur postinjury. METHODS A validated, open-ended shock tube model was used to deliver blast overpressure (150 kPa) to anesthetized rats with body shielding and head fixation, simulating the protective effects of military-grade body armor and isolating a shock wave injury from confounding systemic injury responses, head acceleration, and other elements of explosive events. Evans Blue–labeled albumin was used to visualize blood-brain barrier (BBB) compromise at 4 hours postinjury. Iba1 staining was used to visualize activated microglia and infiltrating macrophages in areas of peak BBB compromise. Acrolein, a potent posttraumatic neurotoxin, was quantified in brain tissue by immunoblotting and in urine through liquid chromatography with tandem mass spectrometry at 1, 2, 3, and 5 days postinjury. Locomotor behavior, motor performance, and short-term memory were assessed with open field, rotarod, and novel object recognition (NOR) paradigms at 24 and 48 hours after the blast. RESULTS Average speed, maximum speed, and distance traveled in an open-field exploration paradigm did not show significant differences in performance between sham-injured and mBINT rats. Likewise, rats with mBINT did not exhibit deficits in maximum revolutions per minute or total run time in a rotarod paradigm. Short-term memory was also unaffected by mBINT in an NOR paradigm. Despite lacking observable motor or cognitive deficits in the acute term, blast-injured rats displayed brain acrolein levels that were significantly elevated for at least 5 days, and acrolein’s glutathione-reduced metabolite, 3-HPMA, was present in urine for 2 days after injury. Additionally, mBINT brain tissue demonstrated BBB damage 4 hours postinjury and colocalized neuroinflammatory changes 24 hours postinjury. CONCLUSIONS This model highlights mBINT’s potential for underlying detrimental physical and biochemical alterations despite the lack of apparent acute symptoms and, by recapitulating the human condition, represents an avenue for further examining the pathophysiology of mBINT. The sustained upregulation of acrolein for days after injury suggests that acrolein may be a...

Acrolein, an endogenous aldehyde, has been shown to be involved in sensory hypersensitivity after rat SCI, for which the pathogenesis is unclear. Acrolein can directly activate a pro-algesic transient receptor protein ankyrin 1 (TRPA1) channel that exists in sensory neurons. Both acrolein and TRPA1 mRNA are elevated post SCI, which contributes to the activation of TRPA1 by acrolein and consequently, neuropathic pain. In the current study, we further showed that, post-SCI elevation of TRPA1 mRNA exists not only in DRGs but also in both peripheral (paw skin) and central endings of primary afferent nerves (dorsal horn of spinal cord). This is the first indication that pain signaling can be over-amplified in the peripheral skin by elevated expressions of TRPA1 following SCI, in addition over-amplification previously seen in the spinal cord and DRG. Furthermore, we show that acrolein alone, in the absence of physical trauma, could lead to the elevation of TRPA1 mRNA at various locations when injected to the spinal cord. Additionally, post-SCI elevation of TRPA1 mRNA could be mitigated using acrolein scavengers. Both of these attributes support the critical role of acrolein in elevating TRPA1 expression through gene regulation. Taken together, these data indicate that acrolein is likely a critical causal factor in heightening pain sensation post-SCI, through both the direct binding of TRPA1 receptor, and also by boosting the expression of TRPA1. Finally, our data also further supports the notion that acrolein scavenging may be an effective therapeutic approach to alleviate neuropathic pain after SCI.