Chronic pain -- pain that continues beyond expected healing time that may or may not be linked with tissue damage -- is a common condition among older (≥65 years) adults, often caused by osteoarthritis (OA) in weight-bearing joints, such as the knee. Older adults with knee OA often experience movement-evoked pain that is associated with reduced mobility, activity avoidance, and social relationship disruption. Knee OA is also associated with increased falls risk, which is a leading cause of injury and mortality among older adults. However, the role of movement-evoked pain in knee OA and falls risk is unclear. It is conceivable that movement-evoked pain contributes to falls risk via impaired neuromuscular function and knee buckling. Thus, better understanding movement-evoked pain might help identify rehabilitation targets to reduce falls risk. While literature demonstrates differences between movement-evoked pain and pain-at-rest, current assessments cannot accurately discern which surveyed pain levels are movement-evoked. Example methodologies that correlate activity and pain levels include pain diaries, accelerometers, or ecological momentary assessment (EMA) surveys. Such methodologies are often dependent on a participant’s ability to recall and differentiate pain experienced in relation to movement, and do not directly assess what movements evoke specific pain levels. The proposed pilot project: (1) develops a protocol for novel trigger-based smartphone EMAs using the Move 4 accelerometer, (2) evaluates the protocol’s feasibility when implemented in older adults with knee OA, and (3) analyzes relationships between movement-evoked pain, knee buckling, and falls. We anticipate that EMA collection will be acceptable for most participants, but are concerned about the accelerometer. The non-invasive Move 4 is capable of triggering EMAs when specific movement thresholds are achieved in real time. Thus, the proposed project addresses a major shortcoming in the field that currently relies on participant recall and does not capture pain levels immediately following specific movement patterns.

Sickle cell disease (SCD), the most common genetic blood disease in North America, can be characterized by recurrent episodes of acute severe pain due to blockages of red blood cells. Without pain self-management habits taught at an early age, the pain faced by youth with SCD can impede both everyday activities and their overall health for the long term, trickling into adulthood. By embedding the skills taught in cognitive-behavioral therapy accessibly in web and mobile-based technology, previous research in this interventional medium shows that this format could be beneficial for youth with SCD. Our research, in particular, investigates the effectiveness of iCanCope SCD, a web and mobile-based pain management program with a focus on helping youth build needed skills to handle pain. This study recruited 160 adolescents aged 12-18 with SCD and randomized the participants into an experimental group for the intervention and an attentional-control group. The innovation includes modules teaching coping strategies, symptom and goal-tracking, and peer-based social support, while the attentional-control will contain static education about SCD. The efficacy of the program is determined through self-report scales at pre-treatment, post-treatment (2 months), and follow-up (6-months) periods, targeting the primary outcomes of adaptive coding, pain reduction, and pain-related disability. Secondary outcomes include physical and emotional functioning and disease-specific health-related quality of life. We hypothesize that adolescents in the iCanCope with SCD experimental group will have an increase in adaptive coding and reduced pain and pain-related disability compared to the control condition. Aside from learning how to structure web-based interventions, I have a role in recoding and organizing participant data for this project. The information collected in this study can help to improve web- and mobile-based interventions for not only youth coping with SCD pain but also those with other pain-related conditions, given the flexibility and universality of cognitive-behavioral frameworks.

The locus coeruleus (LC) is a small nucleus of noradrenergic neurons in the pons, which, despite its size, has broad projections throughout the central nervous system (CNS). Functionally, the LC is believed to be involved in various critical functions, including in the physiological responses to stress and mediating arousal. Previous investigations have demonstrated that optogenetic activation of the LC using channelrhodopsin at a tonic frequency promotes wakefulness in rodents. While this observation causally implicates LC function in wakefulness, it is still not known how the LC is endogenously controlled to mediate arousal. One potential candidate in this control involves the peptide nociceptin and its cognate receptor, the nociceptin opioid peptide receptor (NOPR), both highly expressed around the LC. To investigate, we conducted two pharmacological experiments using the NOPR agonist Ro64-6198 to investigate its effects on locomotion and on the activity of LC noradrenergic neurons. We found that Ro64-6198 (10 mg/kg) strongly reduced open-field locomotor activity compared to vehicle treatment. Using in vivo 2-photon calcium imaging (GCaMP6s), we found that Ro64-6198 (5 mg/kg) profoundly reduced LC noradrenergic neuron activity. Wakefulness appeared reduced in both in vivo experiments. To determine where the endogenous nociceptin signal to the LC originates, we performed an intracranial injection of a Cre-dependent retrograde virus (AAV2-DIO-eYFP) into the LC of a mouse expressing Cre recombinase in nociceptin-expressing neurons. We identified a long-range nociceptinergic projection from the bed nucleus of the stria terminalis (BNST). In order to evaluate how the activity of these BNST neurons are affected by wakefulness, we conducted home-cage fiber photometry recordings. Together, these studies suggest that nociceptin acting on LC noradrenergic neurons reduces arousal, and that the endogenous sources of nociceptin come from the BNST. These experiments shed new light on an understudied endogenous opioid system that may be a druggable target for sleep disorders.

Substance use disorders are shockingly prevalent in the United States, with the Centers for Disease Control and Prevention estimating that in 2019 alone, nearly 50,000 people died from opioid-involved overdoses. Neuropeptide S and its receptor have been previously implicated in drug-seeking behavior, making it an important component in understanding the biological functions underlying addiction. However, such findings have not been localized to any specific region. We set out to investigate the connection between the locus coeruleus, a region with a known population of neuropeptide S producing cells, and the orbitofrontal cortex, a region known to express neuropeptide S receptors. By utilizing an NPSR1-cre mouse line and cre-dependent viral expression, we introduced GCaMP, a fluorescent calcium sensor, into NPSR1 expressing neurons in the orbitofrontal cortex. This enabled us to record calcium fluorescence in vivo as a proxy for neuronal activity. This technique was paired with various behavioral paradigms to explore the endogenous activity of these neurons in natural reward-seeking, social interaction, and fear conditioning. Our results demonstrate that these neurons are activated during cue and food reward-delivery, various social rewards, and foot shock. Aligning these findings with previous research that has demonstrated neuropeptide S’s involvement in drug reward-seeking behavior, we believe these neuropeptide S receptor-expressing neurons in the orbitofrontal cortex could be implicated in drug-seeking behaviors. These findings contribute to the understanding of the neural circuitry involved in substance use disorders, which is integral in continuing the development of treatment options for patients.

Opiate overdose deaths in the US continue to increase at an alarming rate, yet we still only have a partial understanding of the neural mechanisms that regulate opiate addiction. The paraventricular thalamus (PVT) and nucleus accumbens (NAc) are regions of the brain that have both been implicated in addiction to drugs of abuse. Prior studies show that the somatic effects of opioid withdrawal are mediated by excitatory input from the PVT to the NAc. Recently, cannabinoid compounds such as tetrahydrocannabinol (THC), the principle psychoactive constituent of marijuana, has been shown to alleviate effects of opioid withdrawal. Our goal for this project was to determine how cannabinoids regulate the PVT-NAc circuit to modulate these opiate withdrawal symptoms. This study had two principal aims: 1. Understanding the physiological mechanisms by which cannabinoids can modulate PVT-NAc circuits, and 2. Using in-vivo photometry and optogenetics to determine whether we can treat the behavioral effects of opiate withdrawal by using cannabinoid compounds to inhibit the PVT-NAc circuit pathway (n=10 animals, age 12-24 weeks). We first demonstrated that a genetically defined population of anterior PVT (aPVT) neurons expressing the neuropeptide Neurotensin (NTS) sends excitatory projections to the NAc, which are regulated by cannabinoid signaling. Using in-vivo fiber photometry to record activity of aPVT to NAc projections, I showed that rewarding stimuli inhibits the circuit, whereas painful stimuli (such as heat from a hotplate) activate the circuit. Administration of morphine was sufficient to block the pain-induced activation of the aPVT-NAc circuit, and caused robust analgesia. Furthermore, following chronic morphine administration, I used naloxone to precipitate opiate withdrawal, and demonstrated that enhancing cannabinoid signaling was capable of reducing some of the symptoms of opiate withdrawal. Future studies will aim to understand the causal relationship between cannabinoid modulation of the aPVT-NAc circuit and the development of opiate withdrawal.

Substance use disorders contribute to mortality nationwide and are associated with aversive and appetitive behaviors the ventral hippocampus (vCA1) is known to process. The neuromodulators dopamine (DA) and norepinephrine (NE) are also involved, but their release dynamics have not been thoroughly studied in this region. The dorsal hippocampus (dCA1) has similarly weak innervation from the ventral tegmental area (VTA), the major DA source, and the locus coeruleus (LC), the major NE source, and preliminary data in this region suggest an inhibitory effect on DA during salient aversive stimuli and minimal DA release during anxiogenic behaviors. To quantify monoamine release in the vCA1 and determine whether LC-sourced DA can be released there, we intracranially injected Dbh-cre positive mice with one of two biosensors, dlight for DA or GRABNE for NE, in the vCA1, and chrimson, a cre-dependent red-shifted channelrhodopsin, in the LC. A fiber optic lens for optogenetic stimulation and recording was implanted in the vCA1. We recorded dynamics during aversive and appetitive behaviors and found that DA and NE are released in the vCA1 during salient aversive stimuli, and that DA is released and NE release is inhibited during appetitive behaviors. We stimulated chrimson-transfected LC noradrenergic axon terminals while recording neuromodulator dynamics in the vCA1, and found that when stimulated for three seconds at 20 Hz, GRABNE fluorescence increases before slowly returning to baseline, while dlight fluorescence spikes quickly over 10 seconds, then exhibits a secondary, less steep, wave over the next 20 seconds. This secondary wave of DA is not observed in preliminary dCA1 data, indicating that it is unique to this region. In future studies we will investigate the role of the VTA in this secondary release with pharmacological inhibition experiments. These findings reveal distinct monoamine release in the vCA1 during aversive and appetitive behaviors. (Funded by NIMH-R01MH112355)

Neuroligins (NLGNs) are a family of postsynaptic cell adhesion proteins that are essential to the formation and proper functioning of synapses and play a critical role in maintaining neural excitation/ inhibition balance. Neuroligin mutations are linked to several neuropsychiatric disorders like autism, although their role in maladaptive social behavior remains unclear. Inappropriate aggression and agitation are often comorbid with neuropsychiatric disease and understanding the neural pathways underlying aggressive behavior may help to identify potential therapeutic targets. Neuroligin-2 (NLGN-2) specifically supports inhibitory synapse function and plays a key role in regulating social stress behaviors. Here, we examine the role of NLGN-2 in mediating adaptive and maladaptive aggressive behavior in adult male outbred CD-1 mice. In Experiment 1, we use immunohistochemistry to localize and quantify NLGN-2 in Fos-positive cells in nucleus accumbens of mice following resident-intruder reactive aggression. In Experiment 2, we train mice in an operant aggression self-administration procedure and examine changes in NLGN-2 in nucleus accumbens Fos-positive neurons following appetitive, or rewarding, aggression. In Experiment 3, we selectively knockdown NLGN-2 in nucleus accumbens in a neural circuit-specific manner to determine the functional effects of NLGN-2 manipulation on adaptive and maladaptive aggressive behavior. Together, these data demonstrate an important role for nucleus accumbens NLGN-2 in mediating the spectrum of aggressive behavior.