targeted-toxins

Butt AE, Allen K, Arthur K, Cole C, Cook S, Gerth A, Hoichi M, Long C, Noble M, Rea T, Rogers J (2000) A test of negative patterning reveals selective impairment in configural association learning in rats with 192 IgG-saporin lesions of the nucleus basalis magnocellularis. Neuroscience 2000 Abstracts 563.5. Society for Neuroscience, New Orleans, LA.

Summary: We have previously argued that the nucleus basalis magnocellularis (NBM) is selectively involved in configural and not simple association learning, although the experiments used to support our position have involved comparatively non-selective NBM lesions. In the current experiment, rats with bilateral lesions of the NBM created using the highly selective cholinergic immunotoxin 192 IgG-saporin (n = 6) and sham-operated rats (n = 6) were trained in the negative patterning paradigm. In this task, operant responses made in the presence of a light (L) or a tone (T) are reinforced (+) when either stimulus is presented alone, but responses made when these stimuli are presented in compound (LT) are not reinforced (-). We hypothesized that rats in the NBM lesion group would learn to respond to L+ and T+, which requires the ability to learn simple associations, but would fail to learn to withhold responding to the LT- compound, which requires the ability to form configural associations. Responding to L+ and T+ was normal in the NBM lesion group, suggesting an intact ability to learn simple associations, but these animals failed to learn to discriminate between the reinforced stimulus elements L+ and T+ and the nonreinforced compound LT-, suggesting an impairment in configural association learning. The greater level of LT- responding observed in the NBM lesion group did not reflect an overall response disinhibition, as responding during the inter-trial interval did not differ between groups.

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

Ritter S, Dinh TT, Bugarith K (2000) Anti-dβh-saporin injection into the paraventricular nucleus of the hypothalamus selectively abolishes 2DG-induced feeding without causing nonspecific tissue destruction. Neuroscience 2000 Abstracts 502.8. Society for Neuroscience, New Orleans, LA.

Summary: The toxin-antibody complex, saporin conjugated to a monoclonal antibody against dopamine-β-hydroxylase (anti-dβh-sap), selectively destroys dβh-containing catecholamine neurons. Previously we reported that PVH anti-dβh-sap injections abolish feeding and expression of Fos-immunoreactivity (-ir) in the PVH in response to 2DG-induced glucoprivation and cause selective destruction of dβh-containing neurons innervating the hypothalamus. To test the behavioral and neurochemical specificity of this lesion, anti-dβh-sap or control solution (saline or unconjugated saporin) was injected bilaterally into the PVH (n=6 per group). Beginning three weeks later, rats were tested for stimulation of feeding by 2-deoxy-D-glucose (2DG, 200 mg/kg) and mercaptoacetate (MA, 68 mg/kg), which reduce glucose and fatty acid oxidation, respectively, and for suppression of feeding by cholecystokinin octapeptide (CCK, 4 ug/kg). 2DG-induced feeding was abolished by anti-dβh-sap injection, but was not impaired by unconjugated saporin. Neither MA nor CCK responses were altered by anti-dβh-sap. The nonspecific toxicity of anti-dβh-sap at the injection site was assessed. We found that PVH magnocellular neurons at the injection site express oxytocin-ir and do not appear to be disrupted by the anti-βh-sap injection. Further, the ability of PVH neurons at the injection site to express Fos in response to a non-glucoprivic stimulus was not impaired by anti-dβh-sap since lateral ventricular injection of senktide, an NK3 receptor agonist, induced Fos ir in the PVH. PVH injections of anti-dβh-sap impair 2DG-induced feeding and PVH Fos expression by selective destruction of catecholamine neurons. PHS#DK 40498.

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

Secor AJ, Bishop J, Pang KCH (2000) The role of medial septal cholinergic and GABAergic neurons in social memory. Neuroscience 2000 Abstracts 563.6. Society for Neuroscience, New Orleans, LA.

Summary: Electrolytic lesions of the septum alters social behavior, increasing the number of social contacts with a conspecific. Furthermore, lesions of the septum impair both spatial and non-spatial memory. These findings lead researchers to invetigate the role of the septum in social memory. A recent study has demonstrated that administration of vasopressin antagonists into the lateral septum impairs social memory following a 30 minute delay. Social memory was measured as a decreased amount of exploaration of a familiar juvenile compared to a novel juvenile. The present experiment will investigate the role of the cholinergic and GABAergic projection neurons in the medial septum/diagonal band (MS/DB) in social memory. 192-IgG saporin and kainic acid will be administered into the MS/DB to destroy cholinergic and GABAergic MS/DB neurons, respectively. The effects of the drugs on social recognition will be assessed. Each adult rat will be allowed to explore a juvenile rat for 30 seconds. Following various delays (5, 30, 120 minutes), adult rats will be re-exposed to the same or a novel juvenile rat. The amount of time that the adult rat explores the juvenile rat in 1 minute and 3 minute periods will be measured. Differences in exploration time between the control and drug treated rats will provide evidence for alterations in social memory.

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

Siddiq MM, Tsirka SE (2000) Elimination of microglia suggests their involvement in neuronal plasticity. Neuroscience 2000 Abstracts 507.2. Society for Neuroscience, New Orleans, LA.

Summary: Reorganization of mossy fibers occurs in the mammalian hippocampus during consolidation of learning and memory. Induced low level seizures with kainic acid (KA) result in the development of new synapses and the reorganization of existing ones along the mossy fiber pathway. The serine protease tissue plasminogen activator (tPA) is expressed along the mossy fiber pathway and has been implicated in neurite remodeling after stimulation of neuronal activity. Both neurons and microglia secrete tPA. Microglial cells are thought to function only in pathological situations in the CNS, as they exhibit neurotoxic properties. However, a protective role has been observed in the regenerating optic nerve, where intervening activated microglia were involved in tissue remodeling. To investigate whether there is a role for microglia in mossy fiber remodeling, microglia were eliminated in C57/BL6 mice by immunolesioning. The reorganization of mossy fibers was evaluated. Kainate-injected wild-type mice had pronounced mossy fiber reorganization in the dentate gyrus of the hippocampal formation as detected by Timm staining, while the immunolesioned mice had significantly less and shorter mossy fibers. It is therefore suggested that activated microglia may play a role in active remodeling of mossy fibers in the hippocampus after KA-induced seizures.

Related Products: Mac-1-SAP mouse/human (Cat. #IT-06)

Mattsson A, Ögren SO, Olson L (2000) 192 IgG-saporin immunolesioning causes marked facilitation of dopamine-mediated locomotor activity in adult rats. Neuroscience 2000 Abstracts 563.7. Society for Neuroscience, New Orleans, LA.

Summary: Recent studies have indicated a possible link between changes in cholinergic mechanisms and schizophrenia. However there is limited information regarding the functional consequences of changes in ACh transmission on DA functions, which in turn are believed to be involved in schizophrenic symptoms. 192 IgG-saporin targets cells that express the low-affinity p75 neurotrophin receptor. Intracerebroventricular injection causes severe lesions of the cholinergic projections and may also damage Purkinje neurons. We have compared intracerebroventricular injections of 192 IgG SAP to adult rats (5 μg) with injections to neonate rats (0.4 μg day 4 or 0.4 μg day 4 + 0.8 μg day 13). As expected, treated adult rats are markedly impaired in the Morris swim maze both in terms of time to find the platform and in search behavior when the platform is removed, i.e. memory impairment. When tested as adults, neonatally treated animals were only modestly impaired. Interestingly, adult treated animals showed increased spontaneous motility and locomotion and markedly increased locomotor responses to amphetamine (1.5 mg/kg) as evidenced by increased rearing, motility and locomotion. These animals also responded to apomorphine (1 mg/kg) with an increased amount of rearing. There were no marked changes of locomotor activity in rats treated with 192 IgG SAP at 4 days or 4 and 13 days of age. Our results suggest that cholinergic denervation of the forebrain causes a marked enhancement of the behavior responses related to increased dopaminergic activity. However, it cannot be fully excluded that damage to non-cholinergic systems, e.g. Purkinje cells, might contribute to the effects. The striking overreaction to dopaminergic stimuli presumably caused by the cholinergic deficit is possibly relevant in relation to the role of cholinergic malfunctioning in schizophrenia.

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

De Rosa E, Hasselmo ME, Baxter MG (2000) Contribution of the cholinergic basal forebrain to proactive interference between stored odor memories during associative learning in rats: 192 IgG-saporin immunotoxic lesions. Neuroscience 2000 Abstracts 563.8. Society for Neuroscience, New Orleans, LA.

Summary: Previous electrophysiological studies and a computational model suggest that cholinergic neuromodulation may reduce olfactory associative interference during learning (Hasselmo & Bower, 1993; Hasselmo et al., 1992). Using a simultaneous discrimination task where rats were required to learn a baseline odor pair (A+B-) and then two novel odor pairs: A-C+ (with an overlapping component A) and D+E- (with no overlapping component), De Rosa & Hasselmo (2000) demonstrated that a 0.25 mg/kg systemic dose of scopolamine (SCOP) selectively increased proactive interference. Under the influence of SCOP, the rats were impaired on acquiring the odor pair AC and not the odor pair DE relative to their normal saline performance. To localize this effect male Sprague-Dawley rats, with bilateral selective cholinergic lesions of the horizontal limb of the diagonal band of Broca (HDB group) or of all of the cholinergic nuclei of the basal forebrain (BF group), were tested on our task. Neither lesion impaired normal acquisition of either odor pair relative to the sham-operated control rats. However, the BF group, but not the HDB and control groups, were sensitive to a lower dose of SCOP (0.125 mg/kg) than in the previous study: this dose selectively impaired the BF group on acquiring the odor pair AC and not the odor pair DE relative to their normal saline performance, suggesting that weaker cholinergic modulation after removing the majority of cholinergic neurons in the basal forebrain makes the system more sensitive to proactive interference during blockade of remaining cholinergic effects.

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

Rogers SD, Salak-Johnson JL, Schwei MJ, Pomonis JD, Mantyh PW (2000) Reduced anxiety related behavior following ablation of amygdala neurons expressing substance P receptor. Neuroscience 2000 Abstracts 571.2. Society for Neuroscience, New Orleans, LA.

Summary: The neurokinin substance P (SP) is localized in brain regions that coordinate stress response and may play a role in modulating anxiety. Effects of ablation of substance P receptor (SPR)-expressing neurons by administration of a substance P-toxin conjugate, substance P-saporin (SP-SAP), in the amygdala (a brain region known to modulate stress and anxiety responses) were examined immunohistochemically and behaviorally thirty days following SP-SAP treatments. Rats were bilaterally injected in basolateral amygdala nuclei with 5μl of sterile saline, 1 μM saporin (SAP), or 1 μM SP-SAP. SPR-immunofluoresence levels and number of SPR-IR positive neurons in amygdalar subnuclei decreased following SP-SAP treatment. SP-SAP did not induce significant gliosis or non-specific neuronal death. Interestingly, after SP-SAP treatment, the number of NPY-IR neurons were also decreased, and combined SPR and NPY immunofluorescence demonstrated a large number of NPY-IR neurons colocalize with SPR-IR neurons in the amygdala. Thirty days following SP-SAP treatment, rats were tested in elevated plus maze (EPM) and open field (OF). Anxiety level and exploratory behavior displayed by SP-SAP treated rats were altered; they had significantly more entries into and spent more time in EPM open arms than did saline- or SAP-injected rats. In the OF, SP-SAP treated rats spent less time frozen than saline or SAP treated rats. These results suggest that SPR expressing neurons in the amygdala plays a pivotal role in generation of anxiety behaviors and that SP may play a modulatory role in stress-induced anxiety behavior.

Related Products: SP-SAP (Cat. #IT-07)

McGaughy JA, Dalley JW, Robbins TW, Everitt BJ (2000) The behavioral and neurochemical effects of acute and incremental cholinergic lesions on visual attention during a 5-choice serial reaction time task. Neuroscience 2000 Abstracts 563.1. Society for Neuroscience, New Orleans, LA.

Summary: Previously studies have shown that infusions of 192 IgG-saporin (SAP)into the nucleus basal magnocellularis (nbm) produce severe,persistent impairments in visual attention that correlate with the extent of cortical cholinergic deafferentation. After one bilateral infusion of a low dose (0.15 μg/μl; LX1) of SAP into the nbm, rats performing in a 5 CSRTT show specific behavioral impairments when tested with an increased event rate (ITI=2sec). In vivo microdialysis performed while rats were tested under standard conditions (ITI=5sec) in the 5CSRTT showed that LX1 rats had an increased basal acetylcholine (ACH) efflux in the prefrontal cortex (PFC) relative to sham-lesioned animals on the first day of testing, but no difference in task related efflux on either day of testing. The current study investigated the effects of larger cholinergic lesions on attentional perfomance to determine if they would produce large decreases in cortical ACH efflux and consequently impair attention. Rats were trained in a 5 CSRTT prior to receiving intra-nbm infusions of SAP or vehicle (VEH). Lesioned animals were subjected to repeated infusions of a low dose of the toxin (0.15 μg/μl), a single high dose (0.45 μg/μl) or vehicle. The (0.45 μg/μl) dose of SAP produced profound impairments under baseline conditions that correlated with low levels of ACH efflux in the PFC. These impairments were not attenuated by systemic nicotine or physostigmine. The cumulative lesions were hypothesized to increase sensitivity to attentional demands and pharmacological intervention.

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

Janni G, Moallem T, Lappi DA, Ohara PT, Jasmin L (2000) Schwann cells are removed from the rat spinal cord after effecting recovery from paraplegia. Neuroscience 2000 Abstracts 516.8. Society for Neuroscience, New Orleans, LA.

Summary: Remyelination of the CNS is necessary to restore neural function in a number of demyelinating conditions such as multiple sclerosis. Schwann cells, the myelinating cells of the periphery, are good candidates for this purpose, having more robust regenerative properties than their central homologues, the oligodendrocytes. While the ability of Schwann cells to remyelinate the CNS and effect functional recovery has been demonstrated, their long term survival in the CNS after myelinating central axons is largely unknown. We use saporin conjugated to the cholera toxin B-subunit to demyelinate the rat lumbar spinal cord, remove macroglia, and produce paraplegia. This treatment is followed by a spontaneous proliferation of large numbers of endogenous Schwann cells which remyelinate spinal cord axons with concomitant functional recovery from paraplegia within 75 days. During the following weeks, however, quantification on thin sections shows that Schwann cells are progressively replaced by oligodendrocytes, without any lapse in behavioral recovery. This removal of Schwann cells is confirmed by ultrastructural examination and by immunocytochemistry for Schwann cells and oligodendrocytes. Our results indicate that Schwann cell remyelination of the spinal cord might not be permanent. They can be induced to demyelinate and desheath through endogenous mechanisms that remain to be characterized.

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

Winters BD, Dunnett SB (2000) Combined cholinergic denervation of the hippocampus and posterior cingulate cortex fails to impair working memory performance but may produce deficits in behavioural flexibility in the rat. Neuroscience 2000 Abstracts 563.2. Society for Neuroscience, New Orleans, LA.

Summary: Selective cholinergic denervation of either the hippocampal formation (HPC) or posterior cingulate cortex (pCCX) with the immunotoxin 192 IgG-saporin produces negligible effects on rats’ performance of the delayed nonmatching-to-position (DNMTP) task. Yet, fimbria-fornix transection, which disrupts the cholinergic input to both of these limbic regions, causes a delay-dependent deficit in this working memory task. In the current study, rats were trained in a standard DNMTP procedure and then divided into three groups: Group SAP (n=6) received injections of 192 IgG-saporin into both HPC and pCCX; Group NMDA (n=4) received similar injections of the excitotoxin N-methyl-D-aspartic acid; and Control rats (n=10) received vehicle injections. Following surgery, NMDA rats performed significantly worse than SAP and Control rats at all delays in the DNMTP task (p<0.05); SAP rats did not differ from Controls. All groups then acquired a matching-to-position task (i.e., reversal) over four sessions; however, SAP rats performed significantly more perseverative errors during the first reversal session, resulting in a significant Group x Session interaction (p<0.01). It is suggested that, while the cholinergic projections to the HPC and pCCX are not crucial for working memory performance in the DNMTP task, the cholinergic innervation of these limbic regions may influence behavioural flexibility by modulating a circuit mediating habit-like performance.

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