References

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.

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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.

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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.

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Fraley GS (2005) Immunolesions of glucoresponsive projections to the arcuate nucleus alter glucoprivic feeding and luteinizing hormone secretion but not sex behavior in adult male rats. Neuroscience 2005 Abstracts 758.7. Society for Neuroscience, Washington, DC.

Summary: Metabolic signals such as insulin, leptin and glucose are known to alter hypothalamic function. Although insulin and leptin are known to directly alter hypothalamic areas that regulate reproduction, the mechanisms by which glucose alters reproductive function are not as clear. Catecholaminergic neurons in the A1/C1 region of the hindbrain are glucose-responsive and project to the arcuate nucleus. To determine if this pathway is involved in the regulation of sex behavior and luteinizing hormone (LH) secretion, this catecholamingergic pathway was lesioned by injecting saporin conjugated to anti-dopamine-β-hydroxalase (DSAP) or unconjugated saporin (SAP) into the arcuate nucleus of adult male rats. Rats were given glucoprivic challenges then feeding and sex behaviors were observed. As was expected, the DSAP treated rats showed a significant decreased in feeding during glucoprivation (250 mg/kg 2-deoxy-D-glucose, 2DG) compared to SAP controls (p < 0.05). Glucoprivation caused a significant reduction in sex behavior (p < 0.05) in both SAP and DSAP animals equally, compared to saline treatments in either treatment group. At the end of the experiment, animals were given a final challenge with 2DG or saline, killed by decapitation and trunk blood was assayed for plasma LH levels. In SAP animals, 2DG elicited a significant decrease in plasma LH levels (p < 0.05). However, in DSAP animals there was a significant increase (p < 0.05) in plasma LH levels compared to saline-treated rats. These data indicate that the A1/C1 efferents to the ventromedial hypothalamus are involved in the glucostatic regulation of feeding behavior and LH secretion, but not sex behavior in the adult male rat.

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Vijayakumar S, Masood A, Smith M, Clark JP, Nelson DE, Ding JM (2005) Immunolesion of p75 NGF receptor in the mouse SCN attenuated light-induced phase shift of the circadian wheel-running rhythm. Neuroscience 2005 Abstracts 766.18. Society for Neuroscience, Washington, DC.

Summary: Mammalian circadian rhythms are regulated by the suprachiasmatic nucleus (SCN) of the hypothalamus. Alhough the SCN can orchestrate these rhythms in the absence of external cues, it is entrained to environmental cycles through the retinohypothalamic tract. Light-induced phase shifts in circadian rhythm is a classic example of short-term environmental stimuli inducing lasting changes in intracellular signals and gene expression within the SCN cells that alter the phase of the SCN pacemaker and allow entraiment. Since neurotrophins are known to mediate neural plasticity, we investigated the role of brain-derived neurotrophic factor (BDNF) on resetting the phase of the SCN both in vitro and in vivo. We used the SCN brain slice model to study the direct effect of BDNF on the circadian rhythm. Briefly, coronal hypothalamic slices containing the SCN were prepared using 129B/6 mice. The circadian rhythm of the SCN neurons in the brain slice was monitored for 2-3 days by continuously sampling the spike frequencies with single-unit extracellular electrodes. Brief microdrop applications of BDNF (10 uM) induced robust phase delays at CT 16 and phase advances at CT 22. BDNF binds to neurotrophin receptors, including the low affinity p75NTR, which is localized in the SCN. When the toxin Saporin is conjugated to the antibody against p75NTR, it selectively destroys the cells expressing the p75NTR. Three weeks after the stereotaxic injection of the mu p75-Saporin (Advanced Targeting System) into the third ventricle (1 ul over 20 min), the p75NTR immunoreactivity in the mouse SCN is abolished. Immunolesion of the p75NTR in the SCN attenuated light-induced phase delays of the wheel running rhythm at CT16. Consistent with previous findings, our results support a role for BDNF and its receptor p75NTR, in resetting the circadian rhythm of the SCN in mice.

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Greene DM, Castillo MR, Alexander KA, McMahan A, Raap DK, Bult-Ito A (2005) Neurotoxic lesions of serotonin cells in the dorsal raphe reduce compulsive-like nest building in mice. Neuroscience 2005 Abstracts 796.10. Society for Neuroscience, Washington, DC.

Summary: Bi-directional selection for thermoregulatory nest-building behavior in house mice (Mus musculus) has resulted in a 40-fold difference in the amount of cotton used for nest-building between the high and the low selected lines (big and small nest-builders, respectively). The efficacy of serotonin re-uptake inhibitors (SSRIs), especially fluoxetine, for the treatment of obsessive-compulsive disorder (OCD) indicates a serotonergic involvement in the disorder. The repetitive nest-building behavior, characteristic of the big nest-builders, is a compulsive-like behavior that is responsive to SSRI treatment. We investigated the functional involvement of serotonergic pathways in excessive, repetitive nest-building behavior in mice by lesioning serotonergic cells in the dorsal raphe using the neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) or SERT-saporin (Advanced Targeting Systems). 5,7-DHT lesioned mice had a significant decrease in the number of serotonin-stained cells in the dorsal raphe. No decrease was noted in serotonin staining after lesions performed with the SERT-saporin neurotoxin. Mice with successful 5,7-DHT lesions also significantly decreased compulsive-like nest-building as compared to sham and non-surgery controls. These data taken together with additional findings in these mice support the involvement of serotonin pathways in OCD. This data further supports the big nest-builders as a potentially valuable animal model of compulsive behaviors in humans and a means to more clearly identify neurobiological pathways involved in OCD.

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Truitt WA, Oberlin BG, Dietrich AD, Fitz SD, Shekhar A (2005) Neurokinin 1 receptor containing interneurons of the BLA are putative candidates for the inhibitory component of feed-forward inhibition from the mPFC to the BLA. Neuroscience 2005 Abstracts 796.12. Society for Neuroscience, Washington, DC.

Summary: The amygdala and in particular the basolateral nucleus of the amygdala (BLA) is a central site for fear and anxiety. The BLA is under tonic inhibition by a network of inhibitory interneurons. Additionally, cortical inputs can both excite or inhibit the output of the BLA, resulting in increases or decreases in anxiety/fear-like behaviors. In particular mPFC inputs to the BLA can suppress BLA output and inhibit fear conditioning. However, the mechanism by which this occurs is not fully understood. Evidence from electrophysiological studies suggests a feed forward inhibitory relationship between the mPFC and the BLA. This feed forward inhibition putatively occurs by mPFC-glutamatergic inputs exciting GABAergic interneurons of the BLA, which in turn suppress firing of the BLA projection neurons. However, tracing studies demonstrate that the vast majority of mPFC inputs to the BLA form synapses with dendritic spines, which have been reported to exist only on projection neurons of the BLA. Here we present data that suggests a specific subclass of BLA interneurons, those that express neurokinin 1 receptors (NK-1r) are likely candidates for the inhibitory component of the feed forward inhibition described above. Here we report that, in the rat, the NK-1r containing BLA-interneurons contain dendritic spines and NMDA receptors. Furthermore, we report that in anesthetized rats disinhibition of mPFC neurons by injections of bicuculline methiodide (50 pmol), leads to cFos induction in 25 – 50% of the NK-1r containing interneurons in the BLA, while 0% of the NK-1r interneurons expressed cFos following vehicle injections. Furthermore, selective ablation of these NK-1r containing BLA-interneurons (by use of the targeted toxin, SSP-Saporin) suppressed anxiolytic-like effects of familiarity in the SI test. Collectively, these data suggest the NK-1r containing interneurons of the BLA may respond to glutamatergic inputs from the mPFC and may be involved in a mPFC-BLA anxiety or fear regulating pathway.

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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.

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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.

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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)