targeted-toxins

Li A-J, Dinh TT, Wang Q, Wiater MF, Ritter S (2010) Leptin-saporin lesion of hypothalamic arcuate neurons impairs circadian feeding rhythms. Neuroscience 2010 Abstracts 498.6/III29. Society for Neuroscience, San Diego, CA.

Summary: To examine the role of leptin receptor-expressing neurons in the arcuate nucleus (Arc) in circadian control of spontaneous feeding and energy expenditure, we injected a novel targeted toxin, leptin conjugated to saporin (Lep-SAP) into the Arc in rats. Lep-SAP effectively lesioned Arc neurons in a leptin-receptor dependent manner, indicated by an 80% reduction of agouti gene-related protein- or melanocyte-stimulating hormone-immunoreactive neurons in Sprague Dawley rats, but not in leptin receptor deficient Zucker fa/fa rats. Food intake and metabolism were monitored 3-5 weeks after Arc Lep-SAP and control blank-saporin (B-SAP) injections using an Oxymax system. Lep-SAP rats consumed 49% of their total daily intake during the day, compared to 34% in B-SAP rats. Eatograms (feeding actograms), cosinar analysis and Chi-square periodograms of continuous feeding records failed to detect a circadian oscillation in the feeding patterns of Lep-SAP rats, but did detect significant circadian rhythms in B-SAP controls. Unlike feeding, metabolic rate, respiratory exchange ratio and locomotor activity continued to exhibit significant circadian periodicity in both groups, though dampened in amplitude in Lep-SAPs, suggesting that rhythms of feeding and metabolism may be controlled by separate mechanisms. Expression of clock-related genes (Per1 and Bmal1) in hypothalamus, liver and white fat tissue was asynchronous in Lep-SAP rats. These results suggest that leptin-receptive neurons in the Arc exert a critical influence on the circadian patterning of food intake.

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

St Peters MM, Bruno JP, Sarter M (2010) Mesolimbic-basal forebrain circuitry mediating the motivational activation of attention. Neuroscience 2010 Abstracts 506.12/LLL52. Society for Neuroscience, San Diego, CA.

Summary: Prefrontal circuitry mediating cue detection is modulated by the tonic component of cholinergic activity. Performance-associated increases in tonic cholinergic activity are augmented by demands on the cognitive control of attention. Highest levels of tonic cholinergic activity are observed while animals perform below baseline as a result of, for example, a distractor, but while they remain motivated to stabilize and recover attentional performance. Cortico-mesolimbic-basal forebrain circuitry is thought to mediate such motivated activation of attentional performance. We previously observed that stimulation of ionotropic glutamate receptors in the shell of the nucleus accumbens (NAs) stimulates tonic cholinergic activity in the prefrontal cortex. Here we test the hypothesis that such stimulation benefits attentional performance while distractors evoke cognitive control. Rats were trained in an operant sustained attention task (SAT) before undergoing surgery for implantation of a bilateral guide cannula targeting the NAs or, in separate animals, the core of the NA (NAc). NMDA (0.01-0.15 µg/0.5 µL/hemisphere) or vehicle (0.9% saline) was infused bilaterally into task-performing animals during SAT and the more challenging distractor version (dSAT). For the dSAT, the operant chamber ceiling lights flashed on/off at 0.5 Hz during the middle block of three blocks of trials that constituted a session. NMDA infusions in the NAs, but not into the NAc, significantly improved the animals’ attentional performance in the presence of the distractor. These findings are consistent with the hypothesis that activation of the NAs mediates attentional performance under conditions that require top-down control. The next set of experiments determined whether the effects of NAs activation require the cortical cholinergic system. We infused the immunotoxin 192 IgG saporin into prefrontal or parietal regions, in addition to implantation of guide cannula targeting the NAs. Replicating the initial finding, NAs NMDA infusions enhanced dSAT performance. Both PFC and PPC cholinergic deafferentation prevented this effect of NMDA. These findings suggest that the motivated activation of the cholinergic attention system during demands on top-down control modulates fronto-parietal attention networks to optimize attentional performance.

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

Savage ST, Olson L, Mattsson A (2010) Novel object recognition and social interaction in rats lacking cortical cholinergic innervation; comparing manual and digital video tracking systems. Neuroscience 2010 Abstracts 506.9/LLL49. Society for Neuroscience, San Diego, CA.

Summary: Alterations in cholinergic signaling in the brain have been implicated as a contributing factor in the pathogenesis of schizophrenia. We have shown that cholinergic denervation of cortex cerebri by stereotaxic infusion of the immunotoxin 192 IgG-saporin into nucleus basalis magnocellularis in adult rats leads to an enhanced locomotor sensitivity to amphetamine, as well as, a potentiated dopamine release in nucleus accumbens. We have also shown that this cortical cholinergic denervation leads to an increased locomotor response to the NMDA receptor antagonist phencyclidine (PCP), suggesting that disruption of cortical cholinergic activity can lead to disturbances of glutamatergic transmission. We hypothesize that this loss of cortical cholinergic input alters the activity of cortical glutamatergic neurons and in turn, their regulation of subcortical dopamine neurons. In current studies we are investigating memory functions using the novel object recognition task (NOR) and social interaction in adult male Lister hooded rats with cholinergic denervation of neocortex. The behavioral tasks are being conducted under normal conditions and with a PCP-challenge. The data are analyzed both manually by a trained observer, and with a nose point digital video tracking system (Clever Sys Inc.). Manually scoring behavioral data requires extensive observer training, is subject to inter-observer variability, and is time consuming. An automated tracking system could potentially improve upon these issues, however is prone to other problems, including the difficulty of accurately tracking multiple body points. Furthermore, the Lister hooded fur has two different colors which proves difficult for computerized systems to accurately determine the body points. A comparison of the manual scoring and the computerized tracking system is being conducted to determine the most reliable method for each behavioral task. Preliminary results indicate that the cholinergically denervated rats performed the NOR task under normal conditions as well as the controls, however failed to show a preference for the novel object under PCP-challenge. These results were obtained through analysis with both the manual and automated system. Despite fur color difficulties, the video tracking system was able to analyze the NOR task and accurately calculate the distance traveled, which is not easily obtained through manual scoring. These initial results indicate that cortical cholinergic deficits, in addition to a potentiation of the locomotor response to PCP, can also lead to an enhanced sensitivity to PCP-induced cognitive impairments.

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

Datta S, Chatterjee K, Wiley R (2010) Decreasing abnormal nocifensive responses in the bilateral chronic constriction injury (bCCI) model of neuropathic pain: Effects of lumbar intrathecal CCK-saporin. Neuroscience 2010 Abstracts 175.22/MM12. Society for Neuroscience, San Diego, CA.

Summary: The bCCI model produces long lasting -cold hyperalgesia (at least 100 days) along with decreases in staining for cholecystokinin (CCK) in the dorsal horn (DH). Spinal cholecystokinin (CCK) has anti-opiate activity, and selective destruction of DH neurons expressing CCK receptors by injection of intrathecal CCK-saporin, in naïve rats decreases thermal nocifensive reflex responses and is additive with morphine in decreasing nocifensive responses to heat. In the present study, we sought to determine the effects of intrathecal CCK-sap in the bCCI model of neuropathic pain in Long Evans female rats. bCCI rats underwent bilateral ligation of the sciatic nerves with chromic gut sutures. Controls underwent sham surgery with no ligation. Rats were tested on 0.3 C cold plate, thermal preference task (TPT) (shuttle box with floor temperatures of 15 C vs 45 C) and mechanical stimulation (von Frey). bCCI produced increased responses on the cold plate. 21 days after the bCCI surgery, the rats were injected with 1500 ng CCK-sap into the lumber CSF. Then, thermal and mechanical testing was repeated at intervals. Intrathecal CCK-sap injections decreased abnormal nocifensive responding of bCCI rats on the cold plate. CCK-sap reduced withdrawal responses to mechanical stimulation in bCCI rats. In TPT testing, the bCCI animals were hyperalgesic to cold (reduced cold side occupancy). After intrathecal CCK-sap injections, thermal preference was reversed (increased cold side occupancy). We interpret these results as showing that CCK-sap reverses abnormal nocifensive responses of bCCI in rats to aversive cold and mechanical stimuli. These results suggest that silencing CCK receptor-expressing superficial DH neurons is a potential strategy for development of new treatments for chronic neuropathic pain.

Related Products: CCK-SAP (Cat. #IT-31)

Li C, Back S, Lee J, Baek SK, Na H (2010) Gastrin-releasing peptide receptor in the spinal cord mediates mechanical allodynia following nerve injury. Neuroscience 2010 Abstracts 176.2/OO4. Society for Neuroscience, San Diego, CA.

Summary: Gastrin-releasing peptide receptor (GRPR) has been suggested as an itch-specific gene in the spinal cord (Sun et al., Nature, 2009). They described that selective ablation of GRPR-expressing lamina I neurons led to deficits in itch-related scratching behaviors without any effects on pain behaviors including nerve injury-induced mechanical allodynia. It has been known that two types of mechanical allodynia, such as static and dynamic allodynia, can be detectable in neuropathic patients, and may be mediated by distinct mechanisms. In the present study, we investigated the role of spinal GRPR in each of static and dynamic allodynia using both rat- and mouse-tail models of neuropathic pain. Bombesin-saporin (bombesin-sap) was administered intrathecally to ablate spinal GRPR-expressing neurons. Scratching behaviors evoked by pruritogenic agents, such as serotonin and chloroquine, and physiological pain behaviors were analyzed before nerve injury. Static or dynamic allodynia was assessed by the application of von Frey filaments to the tail or brushing the tail with a filament, respectively. RC3095, a GRPR antagonist, was given intrathecally to see its effects on static and dynamic allodynia in neuropathic rats. Bombesin-sap treatment resulted in reduction of GRPR-immunoreactive cells in lamina I of spinal dorsal horn and scratching deficits. Physiological pain behaviors of these animals were not different from those of control animals. Following the partial injury of tail-innervating nerves, animals treated with bombesin-sap exhibited comparable dynamic allodynia to control one. However, they failed to manifest static allodynia during the entire experimental period. In addition, RC3095 relieved static, but not dynamic, allodynia. These findings suggest that spinal GRPR mediates nerve injury-induced static mechanical allodynia as well as itching sensation in normal state.

Related Products: Bombesin-SAP (Cat. #IT-40)

Gulino R, Gulisano M (2010) The recovery of locomotion after lumbar spinal cord motoneuron depletion is affected by the modulation of Sonic Hedgehog and Notch-1 pathways. Neuroscience 2010 Abstracts 259.19/W12. Society for Neuroscience, San Diego, CA.

Summary: Sonic hedgehog (Shh) and Notch-1 are involved in the regulation of stem cell function. Additionally, Notch-1 has a role as modulator of synaptic plasticity. In our previous work, we injected Cholera toxin-B saporin (CTB-sap) into the gastrocnemius muscle to induce a selective depletion of motoneurons within lumbar mice spinal cord (SC) and analysed the expression levels of Shh, Notch-1, Numb, Choline acetyltransferase (ChAT) and Synapsin-I proteins. The functional outcome of the lesion was monitored by grid walk test and rotarod. Shh and Notch-1 appeared reduced in the lesioned tissue and correlated with ChAT and Synapsin-I levels, suggesting a role in modulating synaptic plasticity. Numb expression was also reduced after lesion and appeared correlated with motor performance but not with synaptic plasticity. We sought to determine if the pharmacological manipulation of the expression of Shh and Notch-1 could affect functional recovery by a mechanism involving synaptic plasticity. Therefore, we used CTB-sap to induce lesion as above, and injected Cyclopamine, recombinant Shh or recombinant DLL4 chronically into the intrathecal space by means of osmotic minipumps for two weeks. The functional recovery was monitored for one month after lesion by means of grid walk test, two times a week, whereas the modifications of Shh, Notch-1, ChAT and Synapsin-I protein expression levels were measured by western blot and immunohistochemistry. Here, we show that the modulation of Shh or Notch-1 pathways could affect the recovery of locomotion. Moreover, the molecular mechanisms underlying this process is discussed.

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

Moore JT, Mccarren HS, Beck SG, Kelz MB (2010) Lesioning of the ventrolateral preoptic nucleus alters isoflurane-induced hypnosis in a time-dependent fashion. Neuroscience 2010 Abstracts 300.28/KKK36. Society for Neuroscience, San Diego, CA.

Summary: Despite 160 years of clinical use, the neural mechanisms through which general anesthetics act remain unknown. One possibility is that anesthetics exert their hypnotic effects by acting on the endogenous arousal neural circuitry, including the wake-promoting orexinergic neurons of the hypothalamus and the sleep-promoting GABAergic and galaninergic neurons of the ventrolateral preoptic nucleus (VLPO). We have previously demonstrated that orexinergic neurons play an essential role during emergence from general anesthesia but not during anesthetic induction (Kelz et al., 2008). Here, we present evidence that the VLPO exerted a modulatory role in the induction of anesthetic hypnosis. We used c-Fos immunohistochemistry to analyze the activity of VLPO neurons in brain slices of mice sacrificed after two hours of anesthetic exposure. Whereas anesthetic exposure produced a decrease in the number of c-Fos-positive nuclei in most brain areas, this was not true for the VLPO: exposure to the volatile anesthetics isoflurane or halothane produced a rapid, dose-dependent increase in the number of c-Fos-positive nuclei in the VLPO, implying that hypnotic doses of volatile anesthetics increased the firing rates of VLPO neurons. To determine whether activation of the VLPO was necessary for anesthetic-induced hypnosis, galanin-saporin was used to produce targeted lesions of VLPO neurons. Six days following surgery, the bilaterally lesioned mice were more resistant to induction with isoflurane than control animals in a loss of righting reflex assay. However, 24 days following surgery the lesioned animals were more sensitive to isoflurane than controls. This time-dependent effect was likely due to the build-up of sleep debt–which is known to reduce the anesthetic dose needed to induce hypnosis–as a result of the insomnia-producing VLPO lesions (Lu et al., 2000). These findings are consistent with the VLPO playing a key role in the induction of volatile anesthetic-induced hypnosis, though formal proof will require acute manipulations of VLPO activity that do not produce a sleep debt confound.

Related Products: Galanin-SAP (Cat. #IT-34)

Szot P, Franklin A, White S, Raskind M (2010) Time- and dose-response of 6-hydroxydopamine on locus coeruleus noradrenegric neurons in c57bl/6 mice. Neuroscience 2010 Abstracts 157.20/R1. Society for Neuroscience, San Diego, CA.

Summary: Locus coeruleus (LC) noradrenergic neurons are severely reduced in Alzheimer’s and Parkinson’s disease. However, it is unclear why these neurons are lost and the consequence of this loss on the progression and symptoms of these neurodegenerative disorders. Therefore, establishing an animal model of LC noradrenergic neuronal loss is critical in determining how the LC contributes to these disorders. The purpose of this study was to determine the dose- and time-response of noradrenergic neurotoxicity of 6-hydroydopamine (6OHDA) in adult male C57BL/6 mice. Our laboratory recently demonstrated that DSP4 does not result in a loss of LC noradrenergic neurons. Neurotoxicity of 6OHDA on LC noradrenergic neurons was determined by measuring tyrosine hydroxylase (TH) mRNA expression and TH-immunoreactivity (IR) in LC noradrenergic neurons. TH mRNA was quantitated using MCID (OD), while TH-IR was used to determine if protein levels reflected what was observed with mRNA. 6OHDA (20 µg/µl bilaterally) and dopamine beta-hydroxylase-saporin (DBH-saporin; 1 µg/µl bilaterally) were initially administered into the lateral ventricles (icv) and sacrificed 2 weeks later. 6OHDA reduced TH mRNA and -IR in both the dopaminergic neurons of the substantia nigra (SNpc) and ventral tegmental nucleus (VTA), and LC by -46%, -65% and -63%, respectively. DBH-saporin icv injection did not affect dopaminergic or noradrenergic neurons. Injection of DBH-saporin into the LC (0.1 µg/µl unilaterally) also did not affect LC noradrenergic neurons 2 weeks later. As a time-course 6OHDA (7 µg/µl) was injected unilaterally into the LC (vehicle was administered in the alternate LC) and sacrificed 3 days, 2 and 3 weeks later. A loss of LC noradrenergic neurons was observed only 3 weeks later (-81.4%). 6OHDA was then injected unilaterally into the LC at 7, 10, and 14 ug/ul (vehicle was administered in the alternate LC) and sacrificed 2 weeks later. The 7 µg/µl dose of 6OHDA did not affect TH mRNA in the LC as compared to control side (-19%), 10 ug/ul 6OHDA significantly reduced TH mRNA in the LC by ~55%, and 14 ug/ul 6OHDA dramatically reduced TH mRNA in the LC by ~90%. TH-IR in the LC of the three different 6OHDA doses reflected closely the TH mRNA data. 6OHDA at the dose of 14 µg/µl, which resulted in a near complete loss of LC noradrenergic neurons, did not affect dopaminergic neurons in the SN (-9%) and VTA (+17%). These data indicate that DBH-saporin, at the parameters studied, did not affect mouse LC noradrenergic neurons. 6OHDA demonstrated a time- and dose-response reduction of mouse LC noradrenergic neurons. The consequence of this LC neuronal loss on forebrain noradrenergic markers will also be presented.

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

Ramanathan D, Conner JM, Anilkumar AA, Tuszynski MH (2010) Early post-natal cholinergic lesion impairs normal development and maturation of the motor cortex in rats. Neuroscience 2010 Abstracts 32.14/D20. Society for Neuroscience, San Diego, CA.

Summary: Prior studies have indicated that sensory and motor representations develop over a defined postnatal period and are dependent upon behavioral experience to achieve appropriate adult patterns. In adult animals, behaviorally driven forms of cortical map plasticity are critically dependent upon the basal forebrain cholinergic system. Based on the critical role cholinergic mechanisms play in mediating experience-dependent plasticity in adulthood, we postulated that cholinergic mechanisms may also play a critical role in shaping initial cortical map formation during development. In this study, using 25 male Fisher rats between the ages of 15 days and 60 days, we first characterized the normal motor map development in the rat. We found that motor maps underwent a significant change in overall size and refinement over time, with more mature animals having larger overall maps (p < 0.001) and an increase in the size of distal forelimb representations (p < 0.01). Following the initial characterization of normal motor map development in the rat, we used 192-IgG-saporin (SAP) to create selective cholinergic lesions early in map development (PND 24), in 5 animals (with 6 animals receiving ACSF as controls). This early cholinergic depletion impaired the normal maturation and refinement of cortical motor representations: the total caudal forelimb area (comprising elbow and wrist) was decreased by 33% in cholinergically depleted animals, from 5.1 ± 0.3 mm2 to 3.4 ± 0.3 mm2 (t-test p < 0.01). This decrease in caudal forelimb area in cholinergically-depleted animals was primarily driven by a significant 37% reduction in the size of the distal forelimb (wrist) representation, from 3.1 ± 0.1 mm2 to 2.0 ± 0.1 mm2 (p < 0.001). In a follow-up experiment with 12 additional animals (6 with cholingeric lesions and 6 controls), we found that early (PND 24) cholinergic depletions resulted in long-term impairments in skilled motor learning, with significant differences in daily motor performance beginning at day 3 of training (repeated measures ANOVA < 0.05). These results suggest a novel role for the basal forebrain cholinergic system in establishing normal cortical map formation during development.

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

Sheikh A, Kanold PO (2010) Subplate neurons promote the formation of barrels within rat primary somatosensory cortex. Neuroscience 2010 Abstracts 33.1/E1. Society for Neuroscience, San Diego, CA.

Summary: Subplate neurons are a transient neuronal population present in the neonatal cortex. Subplate neurons receive thalamic afferents and project into the developing cortical plate. Selective removal of subplate neurons in cat visual cortex prevents the normal development of ocular dominance columns and the functional maturation of thalamocortical connections (Ghosh & Shatz 1992, Kanold et al. 2003) . A role of subplate neurons in the development of other sensory cortices is unknown. In rodents, thalamocortical afferents representing the whiskers segregate into barrels in the primary somatosensory cortex (S1). This segregation occurs postnatally and can be disrupted by manipulations of neuronal activity. We previously showed that subplate removal disrupts the development of patterned cortical activity in S1 (Tolner, Yukin, Kaila, Kanold, Abstr. SFN 2009). Thus we hypothesized that disruption of patterned activity in S1 alters the development of barrels. Thus here we investigated if subplate neurons play a role in the development of barrels in rat S1. Subplate neurons were ablated in the somatosensory cortex of rat pups at postnatal day (P) 0 by immunotoxin injections. 10-14 days later we investigated the pattern of barrels in S1 via cytochrome oxidase staining. After subplate ablation there was a disturbance in the barrel patterning when compared to the un-manipulated or control-toxin injected hemispheres. Therefore, subplate neurons are involved in the formation of barrels in S1.

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