References

McGaughy JA, Hutchins DJ, Pimentel AJ, Pimentel CS, Swaine JA (2018) Dissociable effects of noradrenergic and cholinergic lesions of anterior cingulate cortex on distractibility. Neuroscience 2018 Abstracts 238.14 / ZZ15. Society for Neuroscience, San Diego, CA.

Summary: Prior data from our lab and others has shown that that the anterior cingulate cortex (ACC) of the rat is critically involved in many aspects of executive function and cognitive control. Previously, we have shown that excitotoxic lesions of the ACC produced deficits in the ability of male rats to filter salient distractors. Additionally, these same subjects were unable to reverse reinforcement contingencies when tested with complex stimuli (Newman and McGaughy 2011). These deficits in filtering were not attributable to impairments in conditional discrimination learning, impairments in reversal learning with uni-dimensional stimuli or a general distractibility to conspicuous, irrelevant stimuli. In the present study, male, Long-Evans rats were used to determine if lesions to the noradrenergic or cholinergic afferents to ACC could recapitulate the effects of excitotoxic lesions in the same area. Lesions were produced by infusion into rostral ACC of dopamine β hydroxylase saporin or 192 IgG-saporin to deplete norepinephrine or acetylcholine, respectively. After two weeks of recovery from surgery, rats were tested in an intradimensional/extradimensional set-shifting task. This test was selected because of it’s utility in translational neuroscience and it’s sensitivity to several aspects of executive function including susceptibility to salient distractors, the ability to form an attentional set, the ability to shift an attentional set and reversal learning. Preliminary data show that noradrenergic, but not cholinergic lesions recapitulate some, but not all, of the impairments found after excitotoxic lesion of ACC. Specifically noradrenergic lesioned rats were more susceptible to salient distractors than sham-lesioned rats. In contrast to the effects of excitotoxic lesions, noradrenergic lesions did not impair the ability to reverse reinforcement contingencies when using complex stimuli containing salient, irrelevant stimulus dimensions. The extent of the lesions to ACC were assessed using markers for norepinephrine transporters and acetylcholinesterase. Together these data support the hypothesis that norepinephrine in the ACC is critically involved in the ability to filter salient distractors. The significance of these findings will be discussed in terms of the relevance of these data to the treatment of several neuropsychiatric disorders including attention deficit hyperactivity disorder, depression and addiction.

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Cerpa J-C, Marchand AR, Wolff M, Parkes SL, Coutureau E (2018) Noradrenergic modulation of the orbitofrontal cortex mediates flexibility of goal-directed behavior. Neuroscience 2018 Abstracts 325.09 / DDD22. Society for Neuroscience, San Diego, CA.

Summary: For an organism, knowledge of the consequences of its actions and the ability to assign a value to these consequences are both crucial processes allowing an appropriate goal-directed response. The major role of prefrontal regions, e.g. insular and medial prefrontal cortices, for these processes has been very well described. However, the mechanism by which the organism quickly adapt this goal-directed response to unexpected environmental changes remains unknown. It is possible to study this ability using instrumental learning. Typically, during an initial phase, an animal must associate voluntary actions with the delivery of rewarding outcomes. Then, during a reversal phase, the animal must respond flexibly to a modification of these associations. Using this task and chemogenetic tools allowing specific inhibition of cerebral regions, we have recently demonstrated a crucial role of the ventrolateral orbitofrontal cortex (vlOFC) for flexible response adaptation during the reversal phase (Parkes et al., 2017). In the present study, we focused on the noradrenaline (NA) input to the vlOFC which has been commonly implicated in flexibility-requiring tasks. In a first experiment, using a toxin (anti-DβH saporin) we selectively depleted noradrenergic fibers in the vlOFC and showed a deficit of behavioral flexibility. Notably, this effect was not only specific to the reversal phase but also to vlOFC input since a similar depletion restricted to the medial portion of the prefrontal cortex had no effect. Using an intersectional chemogenetic approach aiming at selectively targeting the locus cœruleus (LC) input to the vlOFC, we are deciphering the time course of the involvement of this pathway during behavioural flexibility. Taken together, these results demonstrate a central role for noradrenaline input to the vlOFC in behavioural flexibility and reinforce the idea that the LC exerts a strong modulation of OFC functions.

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Abudukeyoumu N, Garcia-Munoz M, Nakano Y, Arbuthnott GW (2018) Impaired reach-to-grasp responses in mice depleted of striatal cholinergic interneurons. Neuroscience 2018 Abstracts 491.01 / MM13. Society for Neuroscience, San Diego, CA.

Summary: Cholinergic interneurons (ChIs) are sparsely distributed within the striatum, a nucleus that plays important role in voluntary motor control, associated learning, procedural memory, action selection and planning and execution of movement. Sparsely distributed ChIs are 1-3% of all striatal neurons and the main source of striatal acetylcholine. Here we report the effect of depletion of ChIs in the dorsolateral striatum in a reach-to-grasp task. To selectively deplete ChIs, we used the saporin ribosome-inactivating-immunotoxin that targets choline acetyltransferase. C57BL/J male mice, 21 days old, received a stereotaxic unilateral infusion of the toxin (0.3µl/3min), and sham control group was injected with saline. Following one week postsurgery recovery, animals were food deprived for 12 h everyday and trained for 12 days at night during their active circadian cycle. The mean percentage ± SEM of successful performance in the reach-to-grasp task for the last 6 training sessions was 51.11 ± 4.09% (n = 25), 48.79 ± 7.7% (n = 9) and 26.28 ± 5.19% (n = 13) for intact control, sham control and ChIs-depleted mice, respectively. These results indicate that striatal depletion of ChIs impair reaching accuracy, whereas no significant differences were observed in control or sham operated mice. Moreover, a positive correlation between loss of ChIs and performance in the reach-to-grasp task was observed. Our results suggest that the participation of ChIs in striatal mediated motor learning impact on the function of interneurons and projection neurons of the whole striatal microcircuitry (Abudukeyoumu, N., Hernandez-Flores, T. et al. Eur. J. Neuroscience, in press).

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ATS Poster of the Year Winner. Read the featured article in Targeting Trends.

Gulisano M, Vicario N, Costantino A, Giunta MAS, Spitale FM, Parenti R, Gulino R (2018) Sonic hedgehog signalling pathway during regenerative processes in a mouse model of spinal motoneuronal loss. Neuroscience 2018 Abstracts 379.29 / L1. Society for Neuroscience, San Diego, CA.

Summary: Background – Neuronal loss represents the consequence of direct or indirect insults to neurons, as well as one of the major factors mediating persistent disability. Gliosis, neuroinflammation and neurodegeneration are processes in which different cell populations have an interplay mediating both hostile microenvironment and self-repairing mechanisms. Sonic hedgehog (Shh) signaling, which has been indicated as an important pathway in central nervous system development and neural stem cells (NSCs) function, may have a role in prompting the repairing and modulating actions of endogenous and/or exogenous NSCs in neurodegenerative conditions. Methodology – Somatic NSCs were obtained from the subventricular zone (SVZ) of 8 week old female 129/Sv mice. We studied the Shh pathway on NSCs both in vitro and in a mouse model of spinal motorneuronal degeneration induced by cholera toxin B conjugated to saporin (CTB-Sap) injection into the gastrocnemius muscle. Results – NSCs were derived, expanded and characterized in vitro. We analyzed the effects of Shh signaling pathway modulation on NSCs in vitro, finding a significant increase of the NSCs growth rate (2.98±0.58 vs. 5.26±0.57, p<0.05) and neurospheres diameters (109.9±2.4μm vs. 129.6±3.7μm, p<0.01) upon Shh pathway activation. We then characterized Shh signaling activation in CTB-Sap mice analyzing neuronal loss, gliosis, inflammation and compensatory self-repairing mechanisms, compared to intact control mice. Conclusions - Our results suggest a crucial role of Shh signaling during regenerative processes and NSCs as a potential strategy to support recovery after spinal motoneuronal degeneration, thus representing a promising approach for neurodegenerative disorders.

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Cammarata C, DeRosa ED, Anderson AK (2018) Lifespan and cholinergic changes in cognitive flexibility in rats. Neuroscience 2018 Abstracts 512.05 / GGG8. Society for Neuroscience, San Diego, CA.

Summary: The ability to update one’s mental schemas in order respond flexibly and adaptably – i.e. cognitive flexibility – is crucial to navigating a dynamic environment. Proactive interference (PI) is a phenomenon wherein prior memory impedes the formation of new memories for similar information, biasing behavior toward no-longer-relevant schemas. Thus, overcoming PI is an important aspect of cognitive flexibility. PI is exacerbated during aging, and in turn contributes to age-related deficits in cognitive flexibility. In young animals and young adult humans, resolution of PI has been found to rely on neuromodulatory activity via Acetylcholine (ACh), and ACh levels are known to decline in aging, however it has yet to be demonstrated whether these age-related changes in ACh directly contribute to age-related increase in PI. Here, we first compared PI resolution in middle-aged (13 months, n = 8) and old (23 months, n= 11) male Long Evans rats, finding that old animals were more inefficient in resolving PI when compared to the middle-aged animals. Furthermore we performed cholinergic deafferentation, with the immunotoxin 192-IgG saporin (SAP; 0.2 µl of 0.3 µg/µl dissolved in sterile phosphate buffered sale in each of four locations targeting bilateral anterior and posterior basal forebrain), in our older rats (N= 5 SAP and N=6 Sham) which had no effect on the floor performance of older rats. This suggests that the inability to resolve PI seen in the aged rats may be due to already-depleted levels of ACh. We are currently collecting local field potential data in the prelimbic and posterior parietal cortices in behaving older and younger rats and will combine this with central administration of muscarinic cholinergic pharmacology to continue to examine age-related changes in the cortical dynamics that support cognitive flexibility. Based on prior findings in our laboratory examining similar attentional flexibility, we predict the young animals will demonstrate increased beta band LFP activity in the posterior parietal cortex, and potentially increased beta coherence between prefrontal and posterior parietal cortices, related to successful resolution of PI. We expect such activity to be mitigated by cholinergic antagonists and in the older animals.

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Daripelli S, Bhayrapuneni G, Tirumalesetty C, Benade V, Subramanian R, Petlu S, Praveena N, Jayarajan P, Shinde A, Badange R, Bhatta V, Nirogi R (2018) SUVN-G3031, H3 receptor inverse agonist produces wake promoting activity in rats with hypocretin-2-saporin lesions of the lateral hypothalamus. Neuroscience 2018 Abstracts 679.23 / VV4. Society for Neuroscience, San Diego, CA.

Summary: Numerous studies have demonstrated that brain histamine plays a crucial role in maintenance of wakefulness, attention, learning and other cognitive processes. SUVN-G3031, a potent H3 receptor inverse agonist is being developed for the treatment of narcolepsy and other sleep related disorders. SUVN-G3031 is one of the lead molecules with hKi of 8.7 nM and has more than 100 fold selectivity against the related GPCRs. SUVN-G3031 exhibited desired pharmacokinetic properties and brain penetration. SUVN-G3031 blocked R-α-methylhistamine induced water intake and increased tele-methylhistamine levels in brain and cerebrospinal fluid. A single oral administration of SUVN-G3031 produced significant increase in acetylcholine, histamine, dopamine and norepinephrine levels in the cortex. SUVN-G3031 produced wake promoting activity in male Wistar rats. In the present study, effects of SUVN-G3031 on sleep/ wake profile were evaluated in rats with lateral hypothalamic lesion using neurotoxin hypocretin-2-saporin. Narcoleptic-like sleep behavior was observed in rats injected with hypocretin-2-saporin in lateral hypothalamus. SUVN-G3031 produced significant increase in wakefulness with concomitant decrease in rapid eye movement (REM) sleep in these animals. These results are in agreement with electroencephalography (EEG) studies carried out in healthy male Wistar rats. Results from the current study and the neurotransmitter modulations produced by SUVN-G3031 provide a strong basis for the potential of SUVN-G3031 in treatment of sleep related disorders. First in human, Phase 1 studies for SUVN-G3031 are completed underUS IND and SUVN-G3031 has shown desirable pharmacokinetic profile with safety and tolerability in healthy human volunteers. Phase 2 study for narcolepsy is currently being planned.

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Chew C, Sengelaub DR (2018) Exercise is neuroprotective following partial motoneuron depletion: Run for your dendrites. Neuroscience 2018 Abstracts 761.02 / MM11. Society for Neuroscience, San Diego, CA.

Summary: We have previously demonstrated that partial depletion of motoneurons innervating the quadriceps muscles induces dendritic atrophy in remaining motoneurons. Furthermore, systemic treatment with supplemental androgens is neuroprotective and dendritic atrophy following partial motoneuron depletion is attenuated. Circulating levels of androgens have previously been shown to increase following exercise, and exercise has been demonstrated to be neuroprotective in a variety of other neurodegenerative and injury models. Thus, we hypothesized that allowing animals to exercise following partial motoneuron depletion would produce neuroprotective effects similar to treatment with supplemental androgens. Motoneurons innervating the vastus medialis muscle in adult male rats were selectively killed by intramuscular injection of cholera toxin-conjugated saporin. Following saporin injections, some animals were allowed free access to a running wheel attached to their home cages. Four weeks later, motoneurons innervating the ipsilateral vastus lateralis muscle were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in three dimensions. Compared with intact normal males, partial motoneuron depletion resulted in decreased dendritic length in remaining quadriceps motoneurons. Early data suggests that exercise can completely protect against this dendritic atrophy, with exercised males showing dendritic arbors lengths significantly longer than saporin and testosterone-treated animals, and of similar length to intact normal animals. These findings suggest that exercise may be a viable means of protecting against collateral dendritic atrophy. The upregulation of testosterone release following exercise combined with our previous data showing the neuroprotective effects of androgen treatment suggest that the neuroprotective following exercise may be attributable to systemic androgen upregulation.

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Zoccal DB, Silva JN, Barnett WH, Lemes EV, Falquetto B, Colombari E, Molkov YI, Moreira TS, Takakura AC (2018) Interaction between the retrotrapezoid nucleus and the parafacial respiratory group to regulate active expiration and sympathetic activity in rats. Am J Physiol Lung Cell Mol Physiol 315(5):L891-L909. doi: 10.1152/ajplung.00011.2018

Objective: To investigate the microcircuitry responsible for the distribution of the excitatory signals to the the parafacial respiratory group (pFRG) and the the respiratory central pattern generator (rCPG) in conditions of high CO2.

Summary: The activation of the pFRG late-E neurons during hypercapnia require glutamatergic inputs from the RTN neurons that intrinsically detect changes in CO2/pH.

Usage: Bilateral injections of SSP-SAP (0.6 ng in 100 nL of saline per side).

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Qian L, Milne MR, Shepheard S, Rogers ML, Medeiros R, Coulson EJ (2019) Removal of p75 neurotrophin receptor expression from cholinergic basal forebrain neurons reduces amyloid-β plaque deposition and cognitive impairment in aged APP/PS1 mice. Mol Neurobiol 56(7):4639-4652. doi: 10.1007/s12035-018-1404-2

Objective: To investigate the contribution of CBF neuronal p75NTR to the progression of Alzheimer’s Disease

Summary: Data indicate that a direct interaction between CBF-expressed p75NTR and Aβ does not contribute significantly to the regulation of Aβ load.

Usage: To lesion CBF neurons, a single infusion of mu p75-SAP or control Rabbit IgG-SAP (0.4 mg/ml) was stereotaxically-injected into the basal forebrain.

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Garrett AM, Khalil A, Walton DO, Burgess RW (2018) DSCAM promotes self-avoidance in the developing mouse retina by masking the functions of cadherin superfamily members. Proc Natl Acad Sci U S A 115:E10216-E10224. doi: 10.1073/pnas.1809430115

Summary: Focus on DSCAM (Down syndrome cell adhesion molecule 1) self-avoidance function in the mouse retina. DSCAM and members of the cadherin superfamily have also emerged as key contributors to a variety of neurodevelopmental disorders, including autism, schizophrenia, bipolar disease, Down syndrome and intellectual disability.

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