targeted-toxins

Osterlund JR, BLackwell AA, Lipton M, Castillo V, Kartje GL, Tsai S-Y, Wallace DG (2019) Selective loss of septohippocampal cholinergic projections is associated with more circuitous homeward progressions. Neuroscience 2019 Abstracts 789.11. Society for Neuroscience, Chicago, IL.

Summary: Rodents rely on self-movement cues as a source of information to maintain spatial orientation during exploration. The vestibular system provides a source of self-movement cues that are processed by the septohippocampal cholinergic system, and when damaged, disruptions in movement organization are observed. The current study examined the effects of medial septum infusion of 192 IgG-saporin on movement organization during a single exploratory session that limited rats to using only self-movement cues. Rats organize their exploratory behavior into stops and progression. Although stops occur throughout the environment, they tend to cluster within a restricted area indicative of home base establishment. In the current study, movement organization characteristics and home base stability were similar between the lesion and sham groups. However, the lesion group exhibited greater path circuity during progressions returning to the home base. Increases in path circuitry have been implicated in spatial disorientation, indicating a role for medial septum cholinergic projections in processing self-movement cues to maintain spatial orientation. These results provide a foundation for future work to investigate the efficacy of interventions that enhance neuroplasticity within the septohippocampal cholinergic system.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Andrén A, Adermark L, Söderpalm B, Ericson M (2019) An acetylcholine-dopamine interaction in the rat nucleus accumbens and its tentative involvement in ethanol’s dopamine-liberating effect. Neuroscience 2019 Abstracts 079.08. Society for Neuroscience, Chicago, IL.

Summary: Alcohol use disorder is a chronic, relapsing brain disorder associated with serious medical consequences leading to preterm death. Although few in number, cholinergic interneurons (CIN) have arisen as an important cell population within the nucleus accumbens (nAc) that may exert a regulatory impact on dopamine (DA) neurotransmission locally. A defect in CIN have been suggested to be involved in psychiatric diseases such as alcohol addiction. The mechanisms through which endogenous cholinergic activity modulates DA release in response to ethanol administration and its role in development of addiction is not known. In this project, the aim was to study if acetylcholine (ACh) can influence DA release locally in the nAc and if so, through which receptor population(s) this effect is mediated. Further, we wanted to determine the role of ACh in ethanol-induced DA elevation.Using reversed in vivo microdialysis, the acetylcholinesterase inhibitor physostigmine was administered locally in the nAc of male Wistar rats followed by addition of either the muscarinic ACh receptor inhibitor scopolamine or the nicotinergic ACh receptor inhibitor mecamylamine. Subsequently, ethanol was perfused following local pretreatment with scopolamine or mecamylamine, using the same methodology. An immunotoxin, anti-ChAT-saporine, was infused locally into the nAc of a subset of male Wistar rats to selectively lesion CIN, followed by local ethanol administration via reversed in vivo microdialysis. Local administration of physostigmine induced a DA elevation within the nAc, an effect blocked by scopolamine but not by mecamylamine. Local administration of ethanol increased DA levels. Scopolamine pretreatment non-significantly attenuated the ethanol-induced DA elevation, whereas pretreatment with mecamylamine had no effect. Preliminary results indicate a minor attenuation of the DA elevation observed after local administration of ethanol in toxin-treated animals, as compared to sham-treated controls. Taken together, these results suggest that ACh increases extracellular DA levels in nAc in vivo, an effect mediated by muscarinic ACh-receptors and not by nicotinic ACh-receptors. Considering that scopolamine moderately attenuated ethanol-induced DA output and that lesioning of CIN appeared to hamper DA release in response to ethanol, ACh release from CIN within the nAc may be partially involved in ethanol-induced DA release in nAc.

Related Products: Anti-ChAT-SAP (Cat. #IT-42)

Galvan MA, Shramm PA, Bouajram R, Lappi DA, Ancheta LR (2019) A high efficacy selection method for transfected cells utilizing recombinant isolectin B4-saporin. Neuroscience 2019 Abstracts 794.10. Society for Neuroscience, Chicago, IL.

Summary: Transfection protocols often rely on the use of antibiotics for the selection of transfected cells and has become the accepted approach for in vitro research and therapeutic applications. Antibiotics have several shortcomings such as cost, continuous use, and harmful effects — even on the transfected cell population. In addition, selection pressures are often inefficient and fail to provide a population of cells that express the gene of interest (GOI) at high levels. We have used three separate GOI’s to select for solely high-expressing transfectants using targeted toxin selection pressure. Normal Rat Kidney Cells (KNRK) were individually transfected to express green fluorescent protein (GFP), melanopsin or the low-affinity nerve growth factor receptor (p75) using an innovative new transfection delivery vector called pGEI. The results from various assays were utilized to visually determine the expression rate and pattern of the targeted toxin selection method. Melanopsin and p75 — a photopigment and nerve growth factor, respectively — were of great interest to express in our transfected cells as a means to study their role in the development and function of neurons. The delivery vector, pGEI, removes resident Galalpha(1-3)Gal epitopes from non- human mammalian cell surfaces. This residue is the target of recombinant Isolectin B4 – Saporin (IB4-SAP), a selective targeted toxin. IB4-SAP is extremely potent, with an EC50 in the low picomolar range for alpha-D-galactopyranoside expressing cells in vitro. The cells with the highest expression of the inserted vector, and therefore the GOI, will have these residues removed. Those that fail to express the vector or do not express the vector in high enough amounts, will not have all the residues removed, and will be targeted and eliminated via IB4-SAP. This method of selection provides a means of purifying the highest- expressing transfected populations using a more cost-effective and time-saving approach.

Related Products: IB4-SAP (Cat. #IT-10)

Chew C, Sengelaub DR (2019) Exercise is neuroprotective following partial motoneuron depletion via androgen action at the target muscle. Neuroscience 2019 Abstracts 134.13. Society for Neuroscience, Chicago, IL.

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. Blockade of the androgen receptor at the target muscle prevents the neuroprotective effects on motoneuron dendrites in rats treated with supplemental androgens. We have recently shown that exercise is also neuroprotective on motoneuron dendrites following partial motoneuron depletion, and circulating levels of androgens have previously been shown to increase following exercise. Together, these results suggest that exercise may be neuroprotective via androgen action at the muscle. In the present study, we examine whether blockade of androgen receptors at the target musculature would prevent the neuroprotective effects of exercise on dendrites following partial motoneuron depletion. Motoneurons innervating the vastus medialis muscle in adult male rats were selectively killed by intramuscular injection of cholera toxin-conjugated saporin. Simultaneously, some saporin-injected rats were given implants of the androgen receptor antagonist hydroxyflutamide, either directly at the quadriceps musculature or interscapularly as a systemic control. Following saporin injections, some animals were allowed free access to running wheels 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 untreated males, partial motoneuron depletion resulted in decreased dendritic length in remaining quadriceps motoneurons. Early data suggests that following partial motoneuron depletion, exercised males with androgen receptor blockade at the quadriceps show dendritic lengths that are significantly shorter than those of exercised males with no treatment, while dendritic lengths in exercised males with interscapular implants do not differ from those of exercised animals without implants. These findings suggest that exercise may be protective against dendritic atrophy via androgens binding at the target musculature.

Related Products: CTB-SAP (Cat. #IT-14)

Truckenbrod LM, Bumanglag AV, Chun E, Hernandez A, Federico QP, Maurer AP, Sloviter RS, Burke SN (2019) Targeted hippocampal GABA neuron ablation produces hippocampal sclerosis, epilepsy, and dissociable effects on the Morris water maze and object-place paired association tasks. Neuroscience 2019 Abstracts 158.03. Society for Neuroscience, Chicago, IL.

Summary: An epileptogenic role for hippocampal GABAergic dysfunction has recently been reported (Chun et al. 2019). Specifically, selective ablation of hippocampal GABA neurons by Stable Substance P-saporin (SSP-saporin) conjugate caused dorsal hippocampal sclerosis and chronic epilepsy, without involving convulsive status epilepticus or widespread brain injury. The current study assessed cognitive function in chronically epileptic SSP-saporin-treated rats and their vehicle-injected controls ~8 months following injection. First, rats completed the Morris Water Maze test of spatial learning and memory (Morris et al., 1982). Animals then underwent testing with the object-place paired association (OPPA) task, which requires the hippocampus as well as functional connectivity between the hippocampus and cortical areas (Jo and Lee, 2010; Hernandez et al., 2017), and then a simple object discrimination task. Interestingly, both controls and rats with dorsal hippocampal sclerosis and chronic epilepsy were able to learn the location of the hidden platform in the Morris Water Maze task and could also acquire a simple pair-wise object discrimination. However, epileptic rats with dorsal hippocampal sclerosis were significantly impaired on the OPPA task, which requires animals to integrate spatial location memory with a correct object choice and is a more sensitive measure of cognitive dysfunction (Hernandez et al., 2015). These data indicate that, similar to humans with medial temporal lobe epilepsy, selective hippocampal sclerosis and epilepsy in this model do not result in global cognitive decline. Rather, cognitive functions that require functional connectivity between the hippocampus and cortical areas are selectively affected.

Related Products: SSP-SAP (Cat. #IT-11)

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

See Also:

• Chun E et al. Targeted hippocampal GABA neuron ablation by stable substance P-saporin causes hippocampal sclerosis and chronic epilepsy in rats. Epilepsia 60(5):e52-e57, 2019.

Phillips KB, Avila C, Sarter M (2019) Sign-trackers deploy perceptual, but not cholinergic-attentional, mechanisms to respond to salient cues. Neuroscience 2019 Abstracts 331.10. Society for Neuroscience, Chicago, IL.

Summary: Sign-trackers (STs) attribute incentive value to stimuli that predict food and drug rewards and therefore have emerged as a model for studying vulnerability for addiction-like behaviors. Relative to goal-trackers (GTs), who do not imbue discrete predictive stimuli with motivational value, STs also show a reduced capacity for engaging forebrain cholinergic signaling for the processing of behaviorally significant and attention-demanding cues. The greater power of Pavlovian drug cues in STs has been attributed in part to their relatively poor attentional control of such cues. However, when tested in an operant Sustained Attention Task (SAT), STs exhibit only a minor impairment in hit rates but, more robustly, unstable performance over time. These observations raised the question as to the neuro-behavioral or -cognitive mechanisms via which STs perform the SAT. Male and female STs were trained on SAT. The SAT requires the reporting of cues as well as non-cue events via separate levers, yielding four response categories (hits and misses, and correct rejections and false alarms). After reaching criterion, half of STs received bilateral infusions of the cholino-selective neurotoxin 192-IgG saporin while the remaining STs received sham-lesions. Following recovery, performance was assessed on the SAT and a version of SAT incorporating a flashing house light distractor (dSAT). Goal-directed (or top-down) attention is thought to maintain and recover performance during dSAT and mediated via increases in cortical cholinergic activity. In STs, neither SAT nor dSAT performance depended on the integrity of the cholinergic system. We therefore hypothesized that STs perform the SAT using model-free, non-attentional mechanisms, perhaps relying largely on trial-biased perceptual processes to detect salient cues. To test this hypothesis, separate STs and GTs were trained on SAT. The salience of the cue light relative to the house light was varied across operant chambers. In STs, greater perceptual sensitivity reductions were observed as a function of relatively weaker cue salience. In contrast, GTs’ perceptual sensitivity did not relate to cue salience. Associated with their relatively unresponsive cholinergic system, STs rely on perceptual mechanisms, rather than attentional mechanisms, to perform the SAT. The relative absence of (top-down) attentional control of behaviorally significant cues, combined with a propensity to attribute incentive value to such cues, renders STs less likely to reject such cues from guiding their behavior and engaging in alternative action.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Kruashvili L, Beselia G, Chkhikvishvili N (2019) Effect of medial septal selective and non selective lesions on exploratory behavior and recognition memory. Neuroscience 2019 Abstracts 336.01. Society for Neuroscience, Chicago, IL.

Summary: Investigation of cholinergic system and memory interaction has especially become the object of scientific attention due to the clinical and experimental data, in which the severity of dementia in Alzheimer’s disease (AD) was found to have a positive correlation with the extent of the cholinergic loss. The septum is connected to the hippocampus via the fimbria-fomix, which carries projections from the medial septum (MS), and the vertical limb of the diagonal band of Broca. These projections are predominantly cholinergic and GABAergic. Lesions of the fimbria-fomix, or electrolytic lesions of the MS, impair hippocampal- dependent learning and memory. The purpose of this study was to investigate ability to acquire and use spatial (or non-spatial) information as well as to habituate exploratory activity over time in sham-operated, electrolytic, neuro or immunotoxic MS lesioned rats. Methods: A total of 39 male rats were used. For electrolytic lesions a stainless steel was inserted in the MS. All injections were performed stereotaxically. Rats were individually given five 3-min sessions in the open field. All experiments were approved by the Animal Care and Use Committee of the Center and were in accordance with the principles of laboratory animal care. Results: Examination of the AChE stained sections showed that after injections of 192 IgG saporin into the MS, animals exhibited significantly less AChE staining in MS and hippocampus as compared to sections obtained from control animals. The MS electrolytic and ibotenic acid lesioned rats showed an increase in their exploratory activity to the objects and were impaired in habituating to the objects in the repeated spatial environment, rats with immunolesions of the MS did not differ from control rats. Electrolytic lesions of the MS disrupt spatial recognition memory, rats with immuno- or neurotoxic lesions of the MS were normal in detecting spatial novelty. The MS lesioned and control rats clearly reacted to the object novelty by exploring the new object more than familiar ones. Conclusions: MS is sufficient for spatial recognition, but is not sufficient for object recognition memory, the selective loss of septohippocampal cholinergic or noncholinergic projections does not disrupt the function of the hippocampus to a suffi cient extent to impair spatial recognition memory. Therefore, the present study demonstrates dissociation between the two major components (cholinergic and noncholinergic) of the septohippocampal pathway in exploratory behavior assessed in the open field.

Related Products: 192-IgG-SAP (Cat. #IT-01)

Guyenet PG, Stornetta RL, Souza GMPR, Abbott SBG, Shi Y, Bayliss DA. (2019) The retrotrapezoid nucleus: Central chemoreceptor and regulator of breathing automaticity. Trends Neurosci 42(11):807-824. doi: 10.1016/j.tins.2019.09.002

Summary: This review describes the neurons of the retrotrapezoid nucleus (RTN), their transcriptome, developmental lineage, and anatomical projections. The authors also review their contribution to CO2 homeostasis and to the regulation of breathing automaticity during sleep and wake.

Usage: Local injection of SSP-SAP to kill RTN neurons.

Related Products: SSP-SAP (Cat. #IT-11)

Kucinski A, Phillips KB, Koshy Cherian A, Sarter M (2020) Rescuing the attentional performance of rats with cholinergic losses by the M1 positive allosteric modulator TAK-071. Psychopharmacology (Berl) 237(1):137-153. doi: 10.1007/s00213-019-05354-5 PMID: 31620809

Related Products: 192-IgG-SAP (Cat. #IT-01)

Wercberger R, Basbaum AI (2019) Spinal cord projection neurons: A superficial, and also deep, analysis. Curr Opin Physiol 11:109-115. doi: 10.1016/j.cophys.2019.10.002

Summary: Modern approaches to map complex neural circuits require knowledge of the molecular language that defines cell type specificity. However, with few exceptions, NK1R remains the marker consistently used to define projection neurons and even to interrogate their contribution to pain and itch (Mantyh et al.) The first of two studies demonstrating that SP-SAP-mediated ablation of dorsal horn NK1R-expressing neurons reduces injury-induced hyperalgesia. (Carstens et al.) In this paper SP-SAP-mediated ablation of dorsal horn NK1R-expressing neurons reduced pruritogen-evoked scratching.

Related Products: SSP-SAP (Cat. #IT-11)

See Also:

• Mantyh PW et al. Inhibition of hyperalgesia by ablation of lamina I spinal neurons expressing the substance P receptor. Science 278:275-279, 1997.
• Carstens EE et al. Dorsal horn neurons expressing NK-1 receptors mediate scratching in rats. Neuroreport 21:303-308, 2010.