targeted-toxins

Gielow M, Roland J, Servatius, RJ Pang KCH (2010) Do GAT1-saporin lesions of the medial septum damage GABAergic afferents to the medial septum?. Neuroscience 2010 Abstracts 811.3/LLL66. Society for Neuroscience, San Diego, CA.

Summary: 192-IgG saporin is an antibody directed to the p75 receptor conjugated to the ribosomal-inactivating compound saporin. 192-IgG saporin has been widely used to selectively ablate cholinergic cells of the basal forebrain. Cholinergic lesions are typically made by injections of 192-IgG saporin at the soma in basal forebrain nuclei. However, 192-IgG saporin is also effective in damaging specific cholinergic projections by administration of the toxin in the axon terminal region. Recently, GAT1-saporin has been developed as a tool to selectively damage cells expressing the GABA transporter GAT1. GAT1-saporin combines an antibody to the GABA transporter GAT1 with saporin. GAT1 transporters are primarily localized to neurons and GAT1-saporin has been shown to selectively damage GABAergic neurons in the BNST and medial septum. Given the similarity to 192-IgG saporin, a major question is whether GAT1-saporin is effective in damaging GABAergic afferents to the area of administration. Our previous studies found that GAT1-saporin administered to the medial septum / diagonal band of Broca (MSDB) damages GABAergic septohippocampal neurons and impaired performance on delayed match to position tasks. While it seems likely that damage of GABAergic MSDB neurons is responsible for these behavioral impairments, one cannot rule out the possibility that destruction of GABAergic afferents to the MSDB may also contribute. Therefore, the present study was undertaken to determine whether GAT1-saporin lesions of the MSDB damage the GABAergic hippocamposeptal projection. Male Sprague Dawley rats received both fluorogold and either GAT1-saporin or vehicle in medial septum. Immunocytochemistry for choline acetyltransferase and parvalbumin confirmed the extent of the lesion. The majority of hippocamposeptal GABAergic neurons contain the neuropeptide somatostatin. Quantification of double-labeled hippocampal fluorogold-positive cell bodies with anti-somatostatin immunofluorescence was performed using unbiased stereology. Preliminary data suggest that GABAergic hippocamposeptal neurons are intact. These results will be important in understanding the damage produced by GAT1-saporin.

Related Products: GAT1-SAP (Cat. #IT-32)

Matchynski JJ, Lowrance SA, Rossignol J, Dekorver NW, Puckett ND, Pappas CA, Trainor KJ, Delongchamp JL, Radwan J, Heldt JC, Dey ND, Dunbar GL (2010) The effects of a combination of antioxidants and essential fatty acids as treatment for Alzheimer’s disease in the mu-p75 saporin-injected model. Neuroscience 2010 Abstracts 856.15/I21. Society for Neuroscience, San Diego, CA.

Summary: Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that is marked by a progressive loss of memory and affects over five million people nationwide (Alzheimer’s Association, 2010). It is characterized by an increase in oxidative stress, amyloid plaques, neurofibrillary tangles, and the loss of cholinergic neurons. Mice injected with the ribosome deactivating protein, mu-p75 saporin, model the deficits in memory, loss of cholinergic neurons, and increased oxidative stress observed in AD. The current study aimed to decrease the deficits observed in the saporin mouse model using a combination of antioxidants from tart cherries and essential fatty acids, Cerise© total body rhythm (TBR). Mice dosed with TBR or methylcellulose were given bilateral ventricular injections of phosphate buffer saline or saporin. Memory and motor functioning were then measured in a series of behavioural tests. Results indicate that TBR decreased the memory deficits observed in object recognition, place recognition, and Morris-water-maze tasks, as well as the inflammatory response and loss of cholinergic neurons in the medial septum. The findings suggest that TBR could provide an effective, adjunctive treatment that may delay the onset or decrease the severity of AD.

Related Products: mu p75-SAP (Cat. #IT-16)

Hernandez MA, Hernández-Melesio M, Gonzalez-Ezquivel D, Quevedo-Corona L, Jiménez-Cataño M, Santoyo-Pérez M, Rios-Castañeda C, Pérez-Severiano F (2010) Molsidomine promotes the recovery of cognitive deficit induced by 192 IgG saporin in rats. Neuroscience 2010 Abstracts 856.27/I33. Society for Neuroscience, San Diego, CA.

Summary: The NO donor molsidomine (MOLS) has been used as a pharmacological tool in order to antagonize the cognitive deficit associated to cholinergic hypofunction produced by scopolamine. However, the participation of NO in the recovery of cholinergic deficit due to the administration of the cholinergic immunotoxin, 192 IgG saporin (SAP) has not been analyzed. The aim of the present study was to determine the effect of MOLS to counteract the cognitive deficits induced by cholinergic denervation in the object recognition task. Male Wistar rats were divided in the follow experimental groups according to the intraseptal administration of SAP and its vehicle PBS, and the injection (i.p) of the NO donor molsidomine and its vehicle saline: SAP (0.22 µg), PBS (0.1M pH 7.4), molsidomine (4mg/kg), SAP/molsidomine. The single dose of MOLS used in this study antagonized the cognitive failure related to SAP administration and increased the exploration time of novel object. We conclude that MOLS promote the acquisition of recognition memory in the model of cholinergic denervation associated to 192 IgG SAP and further immunohistological studies are being carried out in order to demonstrate that nitric oxide could have an effect over the cholinergic functionality.

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

Lowrance SA, Matchynski JJ, Rossignol J, Dekorver N, Fink K, Salibi P, Dunbar GL (2010) Krx-0501 reduces cognitive deficits in a saporin mouse model of Alzheimer’s disease. Neuroscience 2010 Abstracts 856.8/I14. Society for Neuroscience, San Diego, CA.

Summary: Alzheimer’s disease (AD) is a progressive neurodegenerative disease marked by memory loss and dysfunction of cholinergic neurons. Neurotrophic factors, like nerve growth factor (NGF), have shown to improve cognitive function in AD patients. The inability of NGF to cross the blood brain barrier (BBB) and painful side effects have caused serious concerns over its future use as a treatment. Substituted pyrimidines, such as KRX-0501 (KRX; Keryx Biopharmaceuticals, New York, NY) on the other hand, readily cross the BBB and exert beneficial neurotrophic-like effects in vivo. In this study KRX was administered daily to mice that were given intra-cerebroventricular injections of mu p-75 Saporin (SAP; Advanced Targeting Systems, San Diego, CA) or vehicle (phosphate buffered saline). KRX treatment began at seven weeks of age and continued for 32 days. Doses were set at 10, 15, and 20mg/kg respectively. Animals were tested for cognitive impairment using the Morris water maze (MWM) task, object recognition (OR) and place recognition (PR) tasks while motor deficits were tested using MWM swim speed, rotarod (RR) and the open field (OF) tasks. On day 33 of KRX treatment, mice were sacrificed by transcardial perfusion. In a second experiment, mice received SAP or vehicle surgery and were sacrificed for enzyme-linked immunosorbent assay (ELISA) analysis. MWM results revealed significantly lower escape latencies of control animals relative to SAP animals. In addition mice treated with the low and middle doses of KRX displayed decreased escape latency on the MWM. In the OR task, only mice in the highest treatment group performed significantly above chance levels. No between group differences were seen in the PR task, swim speed, latency to fall from the RR, and distance travelled in the OF. Immunohistochemistry (IHC) using the glial fibrillary acidic protein antibody indicated that astrocyte activation took place primarily around the surgical injection sites. IHC labeling against choline-acetyltransferase revealed a significant decrease in cholinergic neurons of the medial septum. Finally, ELISA protein analysis of midbrain sections revealed that the KRX treatments did not increase levels of endogenous NGF. These results show that SAP injections produced a reproducible destruction of cholinergic neurons, accompanied by memory deficits in the MWM, in the absence of motoric deficits. The KRX treatment attenuated memory deficits, despite unabated cholinergic cell loss in the medial septum, and did so without affecting levels of endogenous NGF.

Related Products: mu p75-SAP (Cat. #IT-16)

Wiater MF, Oostrom M, Barfield R, Dinh TT, Li A-J, Ritter S (2010) Leptin-saporin lesions of the arcuate nucleus induce an arrhythmic circadian feeding pattern. Neuroscience 2010 Abstracts 733.6. Society for Neuroscience, San Diego, CA.

Summary: The endogenous circadian rhythm of feeding is incompletely understood. The leptin sensitive network within the arcuate nucleus (Arc) of the hypothalamus is important for the control of feeding. Genetic deletion of leptin or leptin receptors results in profound obesity, hyperphagia, and the loss of day/night differences in food intake. Because the Arc is critically involved in control of food intake and contains leptin receptors, we hypothesized that the Arc plays an important role in maintenance of feeding rhythms. To examine this hypothesis, we injected a newly developed targeted toxin, leptin conjugated to saporin (LSAP), into the Arc to lesion leptin receptor-expressing neurons in the vicinity of the injection. Controls were injected saporin conjugated to a peptide with no known action or receptor (blank-saporin, BSAP). We expected the Arc LSAP would disrupt the circadian rhythm of food intake, as seen in rats with genetic deletion of leptin or its receptor. Eating rhythms were monitored continuously (each minute) over a 60-day period using BioDAQ (Research Diets) automated meal monitoring equipment. Data were analyzed for circadian rhythm using ClockLab (ActiMetrics) software. Eatograms (food intake in actogram format), showing eating times and durations comparable to actograms used for wheel-running activity, and Chi-square periodograms were generated. Feeding was monitored in light:dark, dark:dark, or light:light conditions. The LSAP injection caused profound hyperphagia, weight gain and disrupted circadian feeding patterns. Although LSAP rats remained sensitive to light and dark under certain circumstances and were capable of an apparent rhythm during light:dark conditions, feeding was arrhythmic by all measures when photic cues were removed (i.e., in dark:dark and light:light conditions). At the end of experimentation, lesions were analyzed using immunohistochemistry to detect agouti gene related protein (AGRP) and α-melanocortin stimulating hormone (α-MSH) neurons, both known to express leptin receptors. Cell bodies positive for these peptides were greatly diminished in the Arc. Results indicate that the Arc contributes importantly to the expression of circadian rhythms of food intake.

Related Products: Leptin-SAP (Cat. #IT-47), Blank-SAP (Cat. #IT-21)

Carvalho AF, Van Bockstaele E (2010) Defining the role of norepinephrine in cannabinoid-induced aversion and anxiety. Neuroscience 2010 Abstracts 833.3. Society for Neuroscience, San Diego, CA.

Summary: In the central nervous system, cannabinoids have been shown to regulate neurotransmitter release, control the hypothalamic-pituitary-adrenal axis and impact several physiological systems, such as food intake, pain and emotion perception. Manipulation of the cannabinoid system using exogenous compounds has been explored as a potential therapeutic for several disorders; however some severe side effects have been reported. Understanding the neural circuits and neurochemical substrates impacted by cannabinoids will provide a better means of gauging their actions within the central nervous system that may contribute to the expression of unwanted side effects. Previous work from our lab had shown that the cannabinoid receptor (CBr) agonist WIN 55,212-2 is able to induce changes in noradrenergic transmission in limbic structures such as prefrontal cortex (PFC) and the nucleus accumbens (Acb). Moreover, we have previously reported that norepinephrine in the nucleus accumbens (Acb) is critical for WIN 55,212-2-induced aversion, as measured by the place conditioning paradigm. In the present study, we further explore the role of norepinephrine in cannabinoid-induced behaviors. More specifically, we investigate whether norepinephrine in the limbic forebrain of rats is important for the anxiety induced by WIN 55,212-2 (3.0 mg/kg, i.p.). Lesion of noradrenergic neurons in the Acb and bed nucleus of the stria terminalis (BNST) was achieved by the intracerebral injection of the toxin saporin conjugated with an antibody that recognizes the enzyme dopamine-beta-hydroxylase (DBH). This toxin yields a specific lesion of noradrenergic neurons. The anxiogenic effects of WIN 55,212-2 were then measured in the elevated zero maze. The results show that depletion of noradrenergic innervation of the Acb and BNST did not reduce the anxiogenic properties of WIN 55,212-2. These results, together with our previous findings, suggest that the anxiogenic and aversive properties of the CBr agonist WIN 55,212-2 are differentially regulated, with the aversive effects being dependent on noradrenergic transmission within the Acb and the anxiogenic effects being regulated by a, yet to be determined, alternative mechanism/circuit.

Related Products: Anti-DBH-SAP (Cat. #IT-03)

Hammond R, Shinde A, Gibbs RB (2010) Effects of basal forebrain cholinergic lesions and estradiol on relative levels of estrogen receptor mRNAs in the rat forebrain. Neuroscience 2010 Abstracts 611.16/MMM67. Society for Neuroscience, San Diego, CA.

Summary: Beneficial effects of estradiol on cognitive performance are lost in response to cholinergic denervation of the hippocampus and frontal cortex. Effects of estradiol also decline with age and time following the loss of ovarian function, which parallels naturally-occurring declines in basal forebrain cholinergic function. We hypothesize that cholinergic impairment may alter the expression of estrogen receptors in specific regions of the brain, thereby decreasing estradiol effects. In the present study, quantitative RT-PCR was used to evaluate the effects of septal cholinergic lesions ± estradiol treatment on relative levels of three estrogen receptors, ERα, ERß, and GPR30. Young adult ovariectomized (OVX) rats received intraseptal injections of saline or 192 IgG-saporin (a selective cholinergic immunotoxin). One week later, rats received either silastic capsules containing 17ß-estradiol or a blank capsule, implanted s.c. Seven days later, rats were killed and the brains were dissected. Tissues from the hippocampus, frontal cortex, prefrontal cortex, striatum, and septum were collected. RNA was extracted and relative levels of ER mRNA determined. Levels within each sample were normalized to levels of GAPDH. Differences between treatments and controls were calculated using the ΔΔCt method. Preliminary data indicate that septal cholinergic lesions produced significant decreases in relative levels of ERα and ERß mRNA in the hippocampus, and an increase in ERß mRNA in the frontal cortex. Estradiol alone produced decreases in levels of ERα, ERß, and GPR30 mRNA in the frontal cortex, decreased levels of ERα and ERß mRNA in the septum, and increased levels of ERα mRNA in the striatum. In rats with cholinergic lesions that also received estradiol, decreased levels of ERα mRNA were detected in hippocampus and septum, and decreased levels of ERß mRNA also were detected in septum. Data suggest that some of the effects of cholinergic denervation on ER mRNA expression may be mitigated by estradiol treatment. These data show that cholinergic lesions significantly affect ER mRNA expression in the brain, and that effects are region-specific. Such effects could account for the loss of beneficial effects of estradiol on cognitive performance in association with age and time following menopause, as well as in association with specific neurodegenerative diseases such as Alzheimer’s disease.

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

Wiater MF, Mukherjee S, Dinh TT, Rooney E, Li A-J, Simasko SM, Ritter S (2010) The arcuate nucleus of the hypothalamus controls the circadian distribution of sleep and feeding. Neuroscience 2010 Abstracts 648.16/H17. Society for Neuroscience, San Diego, CA.

Summary: Integration of daily sleep and feeding rhythms is incompletely understood. We examined the role of the hypothalamic arcuate nucleus (Arc) in these processes using Arc microinjections of the targeted toxin, NPY-saporin (NPY-SAP), or control blank-saporin (B-SAP). NPY-sap targets and destroys NPY receptor-expressing neurons. We monitored 24 hr feeding over a 30-day period beginning 2 wks after the Arc injections, and used EEG recordings to assign vigilance states. Vigilance was divided into rapid-eye movement sleep (REMS), non-REMS (NREMS) and wake. NPY-SAP lesioned rats were hyperphagic , consuming up to 225% of pre-injection baseline. They rapidly became obese. While in the sleep-monitoring chambers, their body weight change per week ranged from 56 ± 9 g to 40.5 ± 4.5g, compared to 6 ± 0.4 g/wk for B-SAP rats. Their circadian pattern of food intake was severely disrupted, such that intake in light and dark periods were approximately equal (43% of their total intake was consumed in the light period vs. 25% in B-SAP controls). Sleep patterns were also significantly disrupted in the NPY-SAP animals. The occurrence of rapid eye movement sleep (REMS) was inverted in phase, occurring mainly at night, rather than during the day. NonREMS was distributed equally across day and night, instead of occurring predominantly during the day. However, 24-hr total REMS and NREMS time was normal. B-SAP controls had normal sleep patterns, with NREMS and REMS occurring predominantly in the light phase. To determine if the change in sleep pattern was due to the change in feeding patterns, we restricted access to food to the dark period for 4 days. NPY-SAP treated animals doubled their food intake in the dark period. However, sleep patterns were not changed compared to the ad libitum feeding period in either NPY-SAP or B-SAP rats. After 7 days of ad libitum feeding, we restricted food access to the light period for 4 days. Again, NPY-SAP animals doubled their intake during the feeding period, this time during the light phase, and sleep patterns were not changed in either group by the restricted feeding. By 100 days post-lesion, the NPY-sap animals were still obese, but the patterning and amount of their food intake were becoming similar to controls. However, when evaluated again, sleep patterns were still altered to the same degree as observed early post-lesion. These results confirm the importance of NPY-receptive Arc neurons in controlling food intake. They also reveal an unexpected role for the Arc in the timing of both NREMS and REMS that appears to be independent of the patterning of food intake.

Related Products: NPY-SAP (Cat. #IT-28), Blank-SAP (Cat. #IT-21)

Khasabov SG, Fliss PM, Rao AS, Simone DA (2010) NK-1 Receptors in the RVM: Involvement in hyperalgesia produced by naloxone but not in morphine analgesia. Neuroscience 2010 Abstracts 678.15/QQ2. Society for Neuroscience, San Diego, CA.

Summary: The rostral ventromedial medulla (RVM) is a crucial supraspinal site for opioid analgesia. Descending modulation of nociceptive transmission by the RVM can be antinociceptive, which is associated with increased activity of OFF cells, or pronociceptive, which is related to activation of ON cells. Analgesia produced by opioids at the RVM level is due to direct inhibition of ON cells and the indirect increase in discharge of OFF cells. A subpopulation of neurons in the RVM (approximately 7%) express neurokinin-1 receptors (NK-1R), which are receptors for substance P (SP). We have shown that NK-1R in the RVM are located primarily on ON cells and contribute to descending facilitation of nociception. We suggest that elimination of NK-1R expressing neurons by the specific saporin toxin conjugate SSP-SAP, will reduce the number of ON cells and thereby decrease descending facilitation without affecting antinociception associated with activity of OFF cells. We therefore determined the contribution of NK-1R expressing neurons in the RVM to changes in nocifensive behaviors produced by morphine or the opioid receptor antagonist naloxone by eliminating NK-1R expressing neurons. Adult male Sprague Dawley rats were pretreated with injection of SSP-SAP (1 µM/0.5 µl) or inactive toxin into the RVM. Ablation of NK-1R possessing neurons was determined histologically and did not alter tale flick or paw withdrawal latencies to heat for up to 4 weeks following treatment, indicating that these neurons do not modulate acute nociception. Morphine (30 µg/0.5 µl) injected into the RVM of control rats or rats pretreated with SSP-SAP increased tail flick latencies approximately 133.5 ± 20.8% and 140.4 ± 8.3%, respectively. The increase in paw withdrawal latency following morphine was also similar between groups. However, injection of naloxone (50 µg/0.5 µl) in control rats decreased tail flick latencies for 90 min with a maximal reduction of 32.2 ± 4.1%, whereas in rats treated with SSP-SAP latencies decreased by 17.8 ± 4.9% and for only 30 min. A similar pattern of effects was found on paw withdrawal latencies to heat. These data support the notion that ON cells possess NK-1Rs and contribute to facilitation of nociceptive transmission.

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

Ferrini F, Mattioli TAM, Lorenzo L-E, Godin A, Wiseman PW, Ribeiro-Da-Silva A, Cahill CM, Milne B, De Koninck Y (2010) Morphine-induced pain hypersensitivity, but not opioid tolerance, depends on microglia-mediated alteration of Cl- homeostasis in spinal dorsal horn. Neuroscience 2010 Abstracts 678.9/PP14. Society for Neuroscience, San Diego, CA.

Summary: Prolonged morphine exposure leads to a reduction of the antinociceptive effect (opioid tolerance) and to an increase in pain sensitivity. Recent evidences suggest that these side effects share similar mechanisms with those underlying neuropathic pain. We have shown that the release of BDNF by activated microglia following peripheral nerve injury causes a decrease in KCC2 activity in the spinal dorsal horn (DH) and weakens Cl−-mediated inhibition through GABAA and glycine receptors. Here, we tested the hypothesis that a similar cascade of events underlies morphine-induced pain hypersensitivity. Adult rats, receiving either morphine (10mg/Kg s.c. twice a day) or saline, were tested for nociceptive thresholds prior to and 1 h after morphine injections each day. Morphine induced tolerance within 2 days and hyperalgesia within 5 days. The hyperalgesia, but not the tolerance, was reversed by intrathecal (i.t.) administration of the anti-mac1 saporin-conjugated antibody (an immunotoxin targeted against microglia) or a TrkB blocking antibody, confirming involvement of both microglia and BDNF in the morphine-dependent hyperalgesia. Microglial activation was confirmed by an increased OX-42 staining after chronic morphine and was blocked by i.t. (-)-naloxone, as well as by (+)-naloxone. Interestingly, (+)-naloxone, while prevented microglia activation, had little effect on morphine tolerance. After 7 days of treatment, rats were sacrificed and DH lamina I-II neurons were recorded by imposing a Cl- load (29 mM). A depolarizing shift in EGABA was observed in lamina I neurons from morphine-treated rats (-42 ± 1 mV, n=6) compared to controls (-50 ± 2 mV, n=5, P<0.05) indicating a weaker Cl- extrusion capacity in these cells. A similar effect was also observed following 3h in vitro incubation of spinal cord slices with morphine (1 μM). No change in EGABA was observed either in the presence of opioid receptor antagonists or the TrkB blocking antibody, confirming the involvement of BDNF in the morphine-signalling pathway. Interestingly, morphine did not produce any change in EGABA in lamina II neurons. To confirm the participation of altered Cl- homeostasis on morphine-induced hyperalgesia in vivo, we administered the carbonic anhydrase inhibitor acetazolamide (i.t.) to minimize the bicarbonate-mediated component of GABAA/glycine currents. Acetazolamide was sufficient to restore inhibition in spinal DH neurons and to reverse the morphine-dependent hyperalgesia. Our data suggest that microglial activation and BDNF release following chronic morphine treatment may alter Cl- extrusion capacity of spinal lamina I neurons and increase pain hypersensitivity.

Related Products: Mac-1-SAP rat (Cat. #IT-33)