Adapting Case Studies for Synchronous and Asynchronous Online Courses

Case studies are an effective active learning method that increases student engagement and are readily adaptable from in-person to online learning environments. In this perspective, Neuroscience Case Network fellows (NeuroCaseNet; NSF-RCN-UBE Grant #1624104) provide specific examples of how case studies were successfully adapted for synchronous and asynchronous online learning, including general strategies and best practices for adapting case studies into both online learning environments.

Cav1.2 L-type calcium channels regulate stress coping behavior via serotonin neurons

Human genetic variation in the gene CACNA1C, which codes for the alpha-1c subunit of Cav1.2 L-type calcium channels (LTCCs), has been broadly associated with enhanced risk for neuropsychiatric disorders including major depression, bipolar and schizophrenia. Little is known about the specific neural circuits through which CACNA1C and Cav1.2 LTCCs impact disease etiology. However, serotonin (5-HT) neurotransmission has been consistently implicated in these neuropsychiatric disorders and Cav1.2 LTCCs may influence 5-HT neuron activity during relevant behavioral states such as stress. We utilized a temporally controlled and 5-HT neuron specific Cacna1c knockout mouse model to assess stress-coping behavior using the forced swim test and dorsal raphe (DR) 5-HT neuron Fos activation. Furthermore, we assessed 5-HT1A receptor function and feedback inhibition of the DR following administration of the 5-HT1A antagonist WAY-100635. We find that 5-HT neuron Cacna1c knockout disrupts active-coping behavior in the forced swim test and that this behavioral effect is rescued by blocking 5-HT1A receptors. Moreover, Cacna1c knockout mice display enhanced Fos expression in caudal DR 5-HT neurons and an enhanced response to a 5-HT1A receptor antagonist in rostral DR 5-HT neurons, indicating that loss of Cacna1c disrupts both 5-HT neuron activation and 5-HT1A dependent feedback inhibition across the caudal to rostral DR. Collectively, these results reveal an important role for 5-HT neuron Cav1.2 LTCCs in stress-coping behavior and 5-HT1A receptor function. This suggests that alterations in CACNA1C function or expression could influence the development or treatment of neuropsychiatric disorder through serotonergic mechanisms.

16p11.2 deletion syndrome mice perseverate with active coping response to acute stress - rescue by blocking 5-HT2A receptors

In humans a chromosomal hemideletion of the 16p11.2 region results in variable neurodevelopmental deficits including developmental delay, intellectual disability, and features of autism spectrum disorder (ASD). Serotonin is implicated in ASD but its role remains enigmatic. In this study we sought to determine if and how abnormalities in serotonin neurotransmission could contribute to the behavioral phenotype of the 16p11.2 deletion syndrome in a mouse model (Del mouse). As ASD is frequently associated with altered response to acute stress and stress may exacerbate repetitive behavior in ASD, we studied the Del mouse behavior in the context of an acute stress using the forced swim test, a paradigm well characterized with respect to serotonin. Del mice perseverated with active coping (swimming) in the forced swim test and failed to adopt passive coping strategies with time as did their wild-type littermates. Analysis of monoamine content by HPLC provided evidence for altered endogenous serotonin neurotransmission in Del mice while there was no effect of genotype on any other monoamine. Moreover, we found that Del mice were highly sensitive to the 5-HT2A antagonists M100907, which at a dose of 0.1 mg/kg normalized their level of active coping and restored the gradual shift to passive coping in the forced swim test. Supporting evidence for altered endogenous serotonin signaling was provided by observations of additional ligand effects including altered forebrain Fos expression. Taken together, these observations indicate notable changes in endogenous serotonin signaling in 16p11.2 deletion mice and support the therapeutic utility of 5-HT2A receptor antagonists.

Altered Cav1.2 function in the Timothy syndrome mouse model produces ascending serotonergic abnormalities

Polymorphism in the gene CACNA1C, encoding the pore-forming subunit of Cav1.2 L-type calcium channels, has one of the strongest genetic linkages to schizophrenia, bipolar disorder and major depressive disorder: psychopathologies in which serotonin signaling has been implicated. Additionally, a gain-of-function mutation in CACNA1C is responsible for the neurodevelopmental disorder Timothy syndrome that presents with prominent behavioral features on the autism spectrum. Given an emerging role for serotonin in the etiology of autism spectrum disorders (ASD), we investigate the relationship between Cav1.2 and the ascending serotonin system in the Timothy syndrome type 2 (TS2-neo) mouse, which displays behavioral features consistent with the core triad of ASD. We find that TS2-neo mice exhibit enhanced serotonin tissue content and axon innervation of the dorsal striatum, as well as decreased serotonin turnover in the amygdala. These regionally specific alterations are accompanied by an enhanced active coping response during acute stress (forced swim), serotonin neuron Fos activity in the caudal dorsal raphe, and serotonin type 1A receptor-dependent feedback inhibition of the rostral dorsal raphe nuclei. Collectively, these results suggest that the global gain-of-function Cav1.2 mutation associated with Timothy syndrome has pleiotropic effects on the ascending serotonin system including neuroanatomical changes, regional differences in forebrain serotonin metabolism and feedback regulatory control mechanisms within the dorsal raphe. Altered activity of the ascending serotonin system continues to emerge as a common neural signature across several ASD mouse models, and the capacity for Cav1.2 L-type calcium channels to impact both serotonin structure and function has important implications for several neuropsychiatric conditions.

Nicotine-induced and D1-receptor-dependent dendritic remodeling in a subset of dorsolateral striatum medium spiny neurons

Nicotine is one of the most addictive substances known, targeting multiple memory systems, including the ventral and dorsal striatum. One form of neuroplasticity commonly associated with nicotine is dendrite remodeling. Nicotine-induced dendritic remodeling of ventral striatal medium spiny neurons (MSNs) is well-documented. Whether MSN dendrites in the dorsal striatum undergo a similar pattern of nicotine-induced structural remodeling is unknown. A morphometric analysis of Golgi-stained MSNs in rat revealed a natural asymmetry in dendritic morphology across the mediolateral axis, with larger, more complex MSNs found in the dorsolateral striatum (DLS). Chronic nicotine produced a lasting (at least 21day) expansion in the dendritic complexity of MSNs in the DLS, but not dorsomedial striatum (DMS). Given prior evidence that MSN subtypes can be distinguished based on dendritic morphology, MSNs were segregated into morphological subpopulations based on the number of primary dendrites. Analysis of these subpopulations revealed that DLS MSNs with more primary dendrites were selectively remodeled by chronic nicotine exposure and remodeling was specific to the distal-most portions of the dendritic arbor. Co-administration of the dopamine D1 receptor (D1R) antagonist SCH23390 completely reversed the selective effects of nicotine on DLS MSN dendrite morphology, supporting a causal role for dopamine signaling at D1 receptors in nicotine-induced dendrite restructuring. Considering the functional importance of the DLS in shaping and expressing habitual behavior, these data support a model in which nicotine induces persistent and selective changes in the circuit connectivity of the DLS that may promote and sustain addiction-related behavior.

The Rodent Forced Swim Test Measures Stress-Coping Strategy, Not Depression-like Behavior

The forced swim test (FST) measures coping strategy to an acute inescapable stress and thus provides unique insight into the neural limb of the stress response. Stress, particularly chronic stress, is a contributing factor to depression in humans and depression is associated with altered response to stress. In addition, drugs that are effective antidepressants in humans typically promote active coping strategy in the FST. As a consequence, passive coping in the FST has become loosely equated with depression and is often referred to as "depression-like" behavior. This terminology oversimplifies complex biology and misrepresents both the utility and limitations of the FST. The FST provides little construct- or face-validity to support an interpretation as "depression-like" behavior. While stress coping and the FST are arguably relevant to depression, there are likely many factors that can influence stress coping strategy. Importantly, there are other neuropsychiatric disorders characterized by altered responses to stress and difficulty in adapting to change. One of these is autism spectrum disorder (ASD), and several mouse genetic models of ASD exhibit altered stress-coping strategies in the FST. Here we review evidence that argues a more thoughtful consideration of the FST, and more precise terminology, would benefit the study of stress and disorders characterized by altered response to stress, which include but are not limited to depression.

Adolescent nicotine induces persisting changes in development of neural connectivity

Adolescent nicotine induces persisting changes in development of neural connectivity. A large number of brain changes occur during adolescence as the CNS matures. These changes suggest that the adolescent brain may still be susceptible to developmental alterations by substances which impact its growth. Here we review recent studies on adolescent nicotine which show that the adolescent brain is differentially sensitive to nicotine-induced alterations in dendritic elaboration, in several brain areas associated with processing reinforcement and emotion, specifically including nucleus accumbens, medial prefrontal cortex, basolateral amygdala, bed nucleus of the stria terminalis, and dentate gyrus. Both sensitivity to nicotine, and specific areas responding to nicotine, differ between adolescent and adult rats, and dendritic changes in response to adolescent nicotine persist into adulthood. Areas sensitive to, and not sensitive to, structural remodeling induced by adolescent nicotine suggest that the remodeling generally corresponds to the extended amygdala. Evidence suggests that dendritic remodeling is accompanied by persisting changes in synaptic connectivity. Modeling, electrophysiological, neurochemical, and behavioral data are consistent with the implication of our anatomical studies showing that adolescent nicotine induces persisting changes in neural connectivity. Emerging data thus suggest that early adolescence is a period when nicotine consumption, presumably mediated by nicotine-elicited changes in patterns of synaptic activity, can sculpt late brain development, with consequent effects on synaptic interconnection patterns and behavior regulation. Adolescent nicotine may induce a more addiction-prone phenotype, and the structures altered by nicotine also subserve some emotional and cognitive functions, which may also be altered. We suggest that dendritic elaboration and associated changes are mediated by activity-dependent synaptogenesis, acting in part through D1DR receptors, in a network activated by nicotine. The adolescent nicotine effects reviewed here suggest that modification of late CNS development constitutes a hazard of adolescent nicotine use.