targeted-toxins

Datta S, Kline IV RH, Wiley RG (2005) Increased formalin behavior after selective destruction of μ opiate receptor-expressing dorsal horn neurons: impaired descending analgesic control?. Neuroscience 2005 Abstracts 623.15. Society for Neuroscience, Washington, DC.

Summary: Spinal intrathecal injection of dermorphin-saporin (derm-sap) selectively destroys dorsal horn neurons expressing the mu-opiate receptor (MOR). In the present study, we sought to determine the effect of derm-sap (500 ng, i.t.) on responses to intraplantar formalin injection (25 ul of 5%). After formalin injection, rats were immediately placed into a clear observation chamber with a video camera beneath the floor. Rats were videotaped for 90 minutes and their behavior scored offline for one minute out of every 5 minutes. 120 minutes after formalin injection rats were anesthetized with pentobarbital and perfused with formalin. Spinal cord sections were stained for MOR and cholecystokinin (CCK) using standard immunoperoxidase techniques on adjacent 40 um sections from L4 spinal segment. Coded sections were used to assess MOR staining intensity by quantitative densitometry. Derm-sap treated rats showed no separation between phase I and II and spent more time than vehicle controls licking/guarding/biting the injected hindpaw during both phase I and II. Derm-sap significantly decreased dorsal horn MOR. Staining for CCK showed time dependant changes after derm-sap which was not present in PBS controls. These same derm-sap treated rats performed normally on hotplate at 44, 47 and 52 C and had normal analgesic responses to systemic morphine on 44, 47 and 52 C hotplates. We interpret these data to indicate that loss of the dorsal horn MOR-expressing neurons reduces the effect of descending analgesic mechanisms. Supported by NIH R21-DA14380 and Department of Veterans Affairs.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

Vera-Portocarrero LP, Xie Y, King T, Lai J, Porreca F (2005) Facilitatory influences from the rostral ventromedial medulla (RVM) are required for pancreatic nociception. Neuroscience 2005 Abstracts 623.18. Society for Neuroscience, Washington, DC.

Summary: Pain is a frequent complaint of patients with pancreatitis or pancreatic cancer. An animal model of pancreatitis induced by dibutyltin dichloride (DBTC) is characterized by abdominal hypersensitivity to mechanical stimuli that appears by day 3 after induction of pancreatitis and persists for at least 10 days. We have used this model to evaluate the role of descending pain modulatory pathways from the RVM in the processing of visceral pain. Pancreatitis was induced in rats by a single tail vein injection of DBTC. Animals were monitored for mechanical sensitivity of the abdominal area as an index of pancreatic nociception using von Frey hairs applied to the surface of the abdomen and recording the frequency of withdrawals from stimulation. Six days after DBTC injection, when mechanical hypersensitivity was fully developed, lidocaine, or saline, was microinjected into the RVM. Lidocaine, but not saline, given into the RVM produced a time-related reversal of mechanical hypersensitivity which peaked by 20 min after injection in animals with pancreatitis. RVM lidocaine had no effect on rats without pancreatitis. A second group of rats received a single microinjection of the cytotoxin dermorphin-saporin into the RVM in order to ablate mu opioid receptor expressing cells that have been proposed to drive descending pain facilitation. 28 days later, the rats received DBTC and their response to mechanical stimulation was monitored daily. These rats showed mechanical hypersensitivity on day 3 after DBTC, but the sensory threshold reverted to normal level by day 6, while rats that had been pretreated with dermorphin, saporin, or water exhibited persistent mechanical hypersensitivity after DBTC out to day 10. These data suggest that a blockade of the descending input from the RVM by lidocaine is sufficient to block the pancreatitis-induced visceral pain, and that the mu opioid receptor expressing cells in the RVM are critical for the persistent pain state.

Related Products: Dermorphin-SAP / MOR-SAP (Cat. #IT-12)

Kozak R, Parikh V, Martinez V, Brown H, Bruno JP, Sarter S (2005) What does acetylcholine do in the posterior parietal cortex (PPC)? Attentional performance-associated increases in PPC ACh efflux. Neuroscience 2005 Abstracts 644.1. Society for Neuroscience, Washington, DC.

Summary: Medial prefrontal cortex (mPFC) ACh efflux has been demonstrated to mediate attentional performance, particularly under conditions that require increases in attentional effort or the processing of distractors. Activation of the mPFC, in part as a result of cholinergic activity, is thought to orchestrate top-down effects for optimization of input processing elsewhere in the cortex. We previously demonstrated that mPFC cholinergic mechanisms influence PPC ACh efflux, suggesting that PPC ACh efflux is a component of the prefrontal circuitry mediating top-down effects. The present experiment was designed to characterize attentional performance-associated increases in PPC ACh efflux in animals performing a regular sustained attention task, following the presentation of a visual distractor, and following loss of cholinergic inputs to the mPFC. Attention task-performing animals were equipped with a guide cannula for insertion of a microdialysis probe and to collect dialysates in the PPC. Cholinergic projections to the mPFC were lesioned bilaterally by infusing 192-IgG saporin into the mPFC. Regular attentional performance was associated with increases in PPC ACh efflux that mirrored those observed previously in the mPFC. In contrast to evidence indicating a cholinergic role in the processing of distractors in the mPFC, PPC ACh efflux was not affected by the distractor and associated impairments in performance. The performance effects of the distractor were augmented in animals with mPFC cholinergic deafferentation. Performance-associated increases in PPC ACh efflux of deafferented animals were higher following the presentation of the distractor than in intact rats. These data support the hypotheses that mPFC cholinergic inputs contribute to the suppression of the effects of distractors and to the recruitment of posterior cortical cholinergic inputs to optimize processing under challenging conditions.

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

Butt AE, Cabrera S, Chavez C, Corley S, Cortez A, Figueroa J, Kitto M, Torner E (2005) Basal forebrain cholinergic lesions produce a dissociation of impairment in delay and trace conditioning in rats. Neuroscience 2005 Abstracts 644.2. Society for Neuroscience, Washington, DC.

Summary: Recent research suggests that Pavlovian trace conditioning, but not delay conditioning, requires awareness or attention, where these processes appear to depend on specific brain systems. For example, Clark, Manns, and Squire (2002) have shown that although amnesiac humans with damage to the hippocampus (HPC) acquire a normal conditioned response (CR) in delay conditioning paradigms where the conditioned stimulus (CS) and unconditioned stimulus (US) partly overlap, they fail to acquire the CR in trace conditioning paradigms where the CS and US are separated in time. Han and colleagues (2003) have shown that the anterior cingulate cortex (ACC) is similarly necessary for trace but not delay conditioning in rats. The medial prefrontal cortex (mPFC) is also involved in trace but not delay conditioning (Kronforst-Collins & Disterhoft, 1998). The basal forebrain cholinergic system (BFCS) has projections to mPFC, ACC, and HPC. Given that each of these regions is critical for trace but not delay conditioning, we hypothesized that lesions of the BFCS using 192 IgG-saporin (SAP) would selectively impair trace but not delay appetitive conditioning in rats. Rats received bilateral injections of SAP or saline only (control group) into BFCS prior to conditioning with a tone CS and sucrose pellet US in either a delay or 10 s trace conditioning paradigm. Preliminary results support this hypothesis. Compared to controls, rats in the BFCS lesion group showed moderate impairment in delay conditioning but more severe impairment in the trace conditioning paradigm. Rats in both groups showed an increase in differential responding to the CS in the delay paradigm, although the BFCS lesion group showed less conditioned responding than controls. In contrast, only the controls showed progressive differential responding to the CS in the trace conditioning paradigm. These data suggest that the BFCS contribute critically to the maintenance of attention in Pavlovian trace conditioning.

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

Fadel J, Frederick-Duus D, Butts R (2005) Orexin lesions block food-related increases in cortical acetylcholine release. Neuroscience 2005 Abstracts 644.8. Society for Neuroscience, Washington, DC.

Summary: Hypothalamic orexin (hypocretin) neurons influence and coordinate arousal, state-dependent behavior, feeding and metabolic processes. Orexin fibers are seen in close proximity to choline acetyltransferase (ChAT)-positive magnocellular somata in portions of the basal forebrain and intrabasalis administration of orexin A increases cortical acetylcholine (ACh) release, suggesting that orexin inputs to the basal forebrain may be important for biasing attentional resources toward stimuli related to underlying homeostatic challenges. Here, we mildly food-deprived rats and trained them to associate an environmental stimulus (darkness) with presentation of palatable food. Microdialysis in these animals showed that the darkness stimulus, with or without accompanying food presentation, produced a robust increase in cortical ACh release. A subset of animals received unilateral administration of the immunotoxin orexin B-saporin (OxB-SAP; 350 ng/0.5 μl) or vehicle into the lateral hypothalamus and perifornical area. OxB-SAP produced a substantial (70-80%) ipsilateral loss of orexin-immunoreactive cells and a corresponding decrease in orexin fiber density in the basal forebrain. OxB-SAP did not alter the number or basal forebrain neurons showing ChAT-immunoreactivity and produced only mild (approximately 15%) loss of melanin-concentrating hormone cells. Basal cortical ACh release was unaffected in lesioned animals, but OxB-SAP lesions abolished increases in cortical ACh release associated with the food-paired stimulus. These data indicate that orexin inputs to the basal forebrain are required for food anticipatory-related increases in cortical ACh release. Orexins appear to be important components of the neural pathways by which interoceptive cues related to homeostasis recruit forebrain attentional systems.

Related Products: Orexin-B-SAP (Cat. #IT-20)

Strait TA, Montoya D, Pang KCH (2005) Role of the medial septum in a repeated acquisition task. Neuroscience 2005 Abstracts 647.14. Society for Neuroscience, Washington, DC.

Summary: The medial septum/diagonal band of Broca (MSDB) provides a major afferent pathway to the hippocampus and both regions are important in learning and memory. The two major projection cells of the MSDB are cholinergic and GABAergic neurons. Although nonselective lesions of the MSDB impair spatial memory, the role of the different MSDB neuronal population in memory is an active area of research. In the present study, rats with preferential cholinergic or GABAergic lesions of the MSDB will be tested on the repeated acquisition task. The task assesses how well a rat can learn the location of a reward that changes from day to day. All sessions are performed on an 8-arm radial arm maze using one arm for reward. Each daily session consists of 5 trials with rats starting from a different arm on each trial. Rats are tested for a total of 9 days; each day a new rewarded arm is used. Our preliminary data suggest that rats with selective cholinergic lesions using 192-IgG saporin are not impaired in acquisition of the task. These results with selective cholinergic lesions contrast with our previous work showing that preferential GABAergic MSDB lesions impair performance of a repeated acquisition task in a water maze. We are currently investigating the effects of preferential GABAergic MSDB lesions on this task. Our preliminary data suggests that cholinergic and GABAergic MSDB neurons may have differential roles in acquisition of a spatial memory task.

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

Lohals R, Veng LM (2005) Cholinergic therapy does not rescue spatial learning deficits induced by ICV injection of 192 IgG-saporin. Neuroscience 2005 Abstracts 653.5. Society for Neuroscience, Washington, DC.

Summary: The cholinergic hypothesis states that central cholinergic dysfunction is responsible for age-dependent cognitive decline. To model this in rats, we induced cholinergic basal forebrain loss the neurotoxin IgG192-saporin (SAP). Following ICV infusion of 2.5 or 5 microgram (ug) SAP, or saline, rats were tested in the radial 12-arm water maze (RAWM), a spatial learning and memory task. While saline sham or 2.5 ug SAP lesioned rats showed normal learning over 4 trials in the RAWM, 5 ug SAP rats were impaired. However, when trained over 20 trials, 5 ug SAP rats eventually attained the same level of performance as 2.5 ug SAP or saline sham rats, and 28 days later all rats showed intact memory for this platform location. In the open field, 5 ug SAP rats failed to habituate. However, SAP or saline sham lesioned rats did not differ in basal activity, rotarod, or visually cued RAWM performance. SAP lesion resulted in severe depletion of ChAT activity in hippocampus and cortex, which significantly correlated with learning impairment in the RAWM. In a second experiment, we used 5 ug ICV SAP to investigate the effect of cholinergic therapy on SAP-induced spatial learning deficits in the RAWM. However, neither galantamine (0.30, 1.25, 5.0 mg/kg) nor RJR-2403 (0.08, 0.31, 1.25 mg/kg) could reverse the SAP induced deficit in RAWM learning. In conclusion, we found that spatial learning in the RAWM was consistently impaired following severe (5.0 ug SAP) cholinergic basal forebrain lesion in rats. This learning deficit was not confounded by general behavioral disturbances. However, with excessive training SAP lesioned rats could learn and later recall spatial information, suggesting that recall is intact in cholinergic lesioned animals. Severe SAP lesion also impaired habituation in an open field and this was not due to hyperactivity. Finally, treatment with galantamine and RJR-2403 did not alleviate the cognitive deficit induced by the SAP lesion, likely due to the severity of cholinergic depletion.

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

Knox DK, Berntson GG (2005) The potential role of the corticopetal cholinergic system in mediating anxiogenic states in rats. Neuroscience 2005 Abstracts 659.10. Society for Neuroscience, Washington, DC.

Summary: Previous research has demonstrated that the corticopetal cholinergic system is important in mediating defensive tachycardia which suggests that this system may be important in mediating aversive states such as fear and anxiety. The aim of this study was to determine how corticopetal cholinergic lesions affect behavioral models of aversive states. The cholinergic immunotoxin 192 IgG saporin (ATS, San Diego CA) was infused into the nucleus basalis of rats in order to accomplish corticopetal cholinergic lesions. Lesioned and control rats were then evaluated on three behavioral models of anxiogenic states: behavior in the elevated plus maze, behavioral suppression induced by classical and contextual fear conditioned stimuli, and heightened arousal induced by a footshock. Lesioned and control rats did not differ on any anxiogenic behavioral measure in the elevated plus maze indicating that corticopetal cholinergic lesions did not affect behavioral indices of unconditional fear. In contrast, both classical and contextual fear conditioned stimuli induced behavioral suppression in control rats, and these effects were attenuated in lesioned rats indicating that corticopetal cholinergic lesions attenuated conditioned fear. Lastly, heightened arousal was evaluated in lesioned and control rats by monitoring behavioral suppression and changes in the electroencephalogram (EEG) over the retrosplenial cortex after a footshock. The footshock induced decreases in the integral area of the delta band and increases in the integral area of the theta band of the EEG in control rats. Both of these effects were attenuated in lesioned rats. In addition, changes in delta and behavioral suppression induced by the footshock were significantly correlated. These results indicated that corticopetal cholinergic lesions attenuated the heightened arousal induced by an aversive event. Taken together, the results of the study suggest that the corticopetal cholinergic system may be important in mediating components of anxiogenic states.

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

Stead S, Trottier N, Doering LC (2005) Characterization of an immunotoxin model of Parkinson’s disease in mice. Neuroscience 2005 Abstracts 664.9. Society for Neuroscience, Washington, DC.

Summary: The primary event underlying the motor deficits of Parkinson’s disease (PD) is degeneration of neurons in the nigro-striatal system. The most widely employed laboratory rodent models of Parkinson’s are the neurotoxin 6-hydroxydopamine (6-OHDA) model that causes acute degeneration of the dopamine neurons in the substantia nigra (SN) and the MPTP mouse model. To date, there is no single model which accurately simulates the pathogenic, histological, biochemical and clinical features relevant for the investigation of PD. Toxins conveyed by axonal transport can be used to make selective lesions in the central nervous system. As previously shown in rats (Wiley et al., Cell. Mol. Biol., 2003), we have found that selective degeneration of the SN can be induced with an immunotoxin consisting of the highly active ribosome inactivating protein Saporin linked to an antibody to the dopamine transporter. A unilateral stereotaxic injection of anti-DAT-Saporin (0.25ug/2ul and 0.05ug/2ul) into the striatum of young (6-8 weeks old) female C57BL6 mice causes a progressive reduction in the number of DA neurons in the SN in comparison to the non-lesioned hemisphere and in various controls. Furthermore, in parallel to the immunohistochemical dopamine neuron death, the animals display a pronounced circling behaviour when challenged with apomorphine (3mg/kg). We are currently examining the affected brain sections for inclusion bodies and changes in astrocytes. This model exhibits the selective deterioration of the nigro-striatal system that occurs in Parkinson’s disease and provides a system to intervene at various stages of dopamine neuron loss and evaluate the effectiveness of stem cell therapy.

Related Products: Anti-DAT-SAP (Cat. #IT-25)

Fargo KN, Sengelaub DR (2005) Testosterone treatment prevents deficits in motor activation caused by partial loss of motoneurons. Neuroscience 2005 Abstracts 672.8. Society for Neuroscience, Washington, DC.

Summary: In male rats, motoneurons of the spinal nucleus of the bulbocavernosus (SNB) project to the bulbocavernosus and levator ani muscles (BC/LA). The SNB system is dependent on androgens for its development, adult morphology, and function. We have previously demonstrated that unilateral depletion of SNB motoneurons induces atrophy of dendrites and somata in contralateral SNB motoneurons, and that this atrophy is prevented by treatment with exogenous testosterone. In the present experiment, we tested the hypothesis that this neuroprotective effect of testosterone on the morphology of SNB motoneurons is accompanied by a neuroprotective effect on the electrophysiological function of the system. We unilaterally depleted right-side SNB motoneurons by intramuscular injection of cholera toxin-conjugated saporin. Simultaneously, some of the saporin-injected rats were castrated and immediately given exogenous testosterone in subcutaneous Silastic capsules designed to produce testosterone titers in the high-normal physiological range. Four weeks later, animals were anesthetized and spinally transected. A stimulating electrode was placed on the left L6 dorsal root, which carries motor afferents from the BC/LA, and a recording electrode was placed on the motor branch of the left pudendal nerve, which carries SNB motoneuron axons to the BC/LA. Both nerves were then severed distal to electrode placement, and recruitment curves were generated by stimulating through the entire range of effective intensities. Consistent with our previously reported morphological changes, unilateral motoneuron depletion resulted in an attenuation of the recruitment of motoneurons in the contralateral SNB, and this was completely prevented by treatment with exogenous testosterone. This result provides a functional correlate to the neuroprotective effects of testosterone treatment on SNB morphology following unilateral motoneuron depletion, further supporting a role for testosterone as a neurotherapeutic agent in the injured nervous system.

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