sfn2003

Fargo KN, Sengelaub DR (2003) Testosterone treatment protects motoneurons from dendritic atrophy following contralateral motoneuron depletion. Neuroscience 2003 Abstracts 602.2. Society for Neuroscience, New Orleans, LA.

Summary: In male rats, motoneurons of the spinal nucleus of the bulbocavernosus (SNB) project to the bulbocavernosus and levator ani muscles. SNB motoneurons and their target muscles are dependent on testosterone (T). We have previously demonstrated that unilateral depletion of SNB motoneurons induces dendritic atrophy in contralateral SNB motoneurons, and this atrophy is prevented by androgen manipulation. In the previous study, males were castrated for 6 weeks, then given replacement T coincident with motoneuron depletion. Because castration results in SNB dendritic retraction, and T replacement causes SNB dendrites to regrow to normal length, it is possible that the regressive changes or the active regrowth are involved in the protective effect of T manipulation. Alternatively, it may be that the effect can be accounted for simply by the high-normal levels of T produced by hormone implants. In the present experiment we show that SNB motoneuron dendrites are protected from contralateral motoneuron depletion by exogenous T alone (i.e., with no delay between castration and T replacement). We unilaterally depleted SNB motoneurons in male rats by intramuscular injection of cholera toxin conjugated saporin. Simultaneously, some saporin-injected rats were castrated and immediately given implants containing T. Four weeks later, contralateral SNB motoneurons were labeled with cholera toxin conjugated HRP, and dendritic arbors were reconstructed in 3 dimensions. A group of intact control males was also used. Contralateral SNB motoneuron depletion induced dendritic retraction to about 40% of normal length, but this atrophy was completely prevented by T treatment. Thus, the protective effect of T on SNB motoneurons is not due to prior dendritic retraction or T-induced regrowth per se. Instead, the presence of high-normal levels of T prevents dendritic retraction induced by contralateral motoneuron depletion.

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

Chance WT, Dayal R, Friend LA, Sheriff S (2003) Normalization of burn-induced hypermetabolism following 3rd ventricle injection of saporin-CRF conjugate. Neuroscience 2003 Abstracts 614.5. Society for Neuroscience, New Orleans, LA.

Summary: The development of hypermetabolism following major burn trauma presents significant problems for patient management and recovery. To better understand CNS mediation of burn-induced hypermetabolism, we disrupted CRF neurotransmission by injecting a conjugate of CRF to the ribosome toxin, saporin, into the 3rd ventricle of burned and control rats. Following anesthetization (ketamine/xylazine; 80/15 mg/kg), cannulae (24 ga) were implanted into the 3rd ventricle of 58 adult, male, SD rats. Two weeks later, these rats were anesthetized again and subjected either to a 25 sec, open-flame, full-thickness burn or sham-burn procedures. One week later, the rats were divided into groups to receive ivt injections of artificial CSF (5 ul), saporin (2.5 ug) or saporin-CRF (2.5 ug). Resting energy expenditure (REE) was determined by indirect calorimetry for 60 min on all rats 14 days post-burn. Burned rats treated with CSF exhibited significantly (p<0.01) increased REE (164 ± 4 vs 132 ± 7 kcal/kg/day). Although the saporin treatment had no effect in burned (175 ± 6 kcal/kg/day) or sham-burned (133 ± 10 kcal/kg/day) rats, REE was reduced (p<0.01)in the burned rats treated with the saporin-CRF conjugate (145 ± 6 kcal/kg/day). CRF-induced (1 ug) increase in REE was also prevented in saporin-CRF-treated sham-burned rats. Determination of hypothalamic CRF receptor mRNA by RT-PCR suggested that CRF-R2 expression was reduced in saporin-CRF-treated rats, while CRF-R1 expression was not affected. These results suggest that hypothalamic CRF activity is involved in the maintenance of burn-induced hypermetabolism, and the CRF-2 receptor is important for the expression of this increase in REE. Therefore, control of hypermetabolism may be possible using selective CRF-R2 antagonists.

Related Products: CRF-SAP (Cat. #IT-13)

Li AJ, Ritter S (2003) 2-deoxy-D-glucose (2DG) increases NPY mRNA expression in hindbrain neurons. Neuroscience 2003 Abstracts 615.7. Society for Neuroscience, New Orleans, LA.

Summary: Previous results suggest that the orexigenic peptide, neuropeptide Y (NPY), participates in glucoprivic feeding. NPY mRNA in the hypothalamus is increased by glucoprivation (Sergeyev et al, 2000; Fraley and Ritter, 2003) and injection of anti-NPY antibody into the paraventricular nucleus of the hypothalamus (PVH) impairs glucoprivic feeding (He and Edwards, 1998). The hypothalamus is innervated by both arcuate and hindbrain NPY cell bodies. NPY innervation from the hindbrain is substantial and is derived largely or entirely from cell bodies that co-express norepinephrine or epinephrine. Selective immunotoxin lesions have demonstrated that these hindbrain catecholamine neurons are required for glucoprivic feeding (Ritter et al., 2001), as well as for glucoprivic stimulation of corticosterone secretion (Ritter et al., 2003) and suppression of estrus (I’Anson et al., 2003). However, the specific contribution of hindbrain NPY to these glucoregulatory responses has not been examined. Therefore, we examined NPY mRNA expression in hindbrain catecholamine cell groups 1.5 hr after 2-deoxy-D-glucose (2DG, 250 mg/kg) injection using in situ hybridization. Cell groups A1, A1/C1, the middle portion of C1 and C2, showed a basal level of NPY mRNA signal that was dramatically increased by 2DG. In rostral C1 and in C3, where basal NPY mRNA expression was below detection threshold, the hybridization signal was also significantly increased by 2DG. In cell groups A2, A5, A6 and A7, neither basal nor 2DG-stimulated NPY mRNA expression was detected. PVH microinjection of the retrogradely transported catecholamine immunotoxin, saporin conjugated to anti-dopamine-β-hydroxylase, destroyed hindbrain catecholamine neurons and abolished basal and 2DG-stimulated increases in NPY expression in hindbrain cell groups. These data suggest that hindbrain NPY neurons with projections to the hypothalamus participate in glucoprivic feeding and other glucoregulatory responses.

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

Gerashchenko D, Murillo-Rodriguez E, Lin L, Xu M, Hallett L, Nishino S, Mignot E, Shiromani PJ (2003) Relationship between CSF hypocretin levels and hypocretin neuronal loss. Neuroscience 2003 Abstracts 616.2. Society for Neuroscience, New Orleans, LA.

Summary: In the sleep disorder narcolepsy there is a massive reduction in the number of neurons containing the neuropeptide, hypocretin (HCRT). Most narcoleptic patients also have low to negligible levels of HCRT in the cerebrospinal fluid (CSF). However, the relationship between HCRT neurons and HCRT levels is not known, making it difficult for investigators to estimate how many HCRT-containing neurons might be present based on measurements of CSF HCRT levels. A relationship between neuronal loss and CSF levels of the ligand is known in other degenerative diseases, such as Parkinson’s, but not in narcolepsy. To identify this relationship, hypocretin-2-saporin, the neurotoxin that kills hypocretin neurons, or saline were administered to the lateral hypothalamus and CSF was extracted at zeitgeber times (ZT) 0 (time of lights-on) or ZT 8 at various intervals (2, 4, 6, 12, 21, 36, 60 days) after the neurotoxin administration. Compared to saline animals (n=8), rats with an average loss of 73% of HCRT neurons (n=9) had a 50% decline in CSF HCRT levels on day 60. The decline in HCRT levels was evident by day 6 and there was no recovery or further decrease. The decline in HCRT was correlated with increased REM sleep. Rats with an average loss of 14.4% of HCRT neurons (n=4) showed no significant decline in CSF HCRT levels compared to saline rats. In rats with 73% loss of HCRT neurons, the HCRT levels were not substantially increased by 6h prolonged wakefulness indicating that surviving neurons were not able to increase the output of HCRT to compensate for the HCRT neuronal loss. From these data we conclude that since most narcoleptics have more than 80% reduction of CSF HCRT that in these patients most HCRT neurons are lost.

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

Pan S, Borowski T, de Lacalle S (2003) Sleep deprivation impairs retention performance on an olfactory discrimination task. Neuroscience 2003 Abstracts 616.21. Society for Neuroscience, New Orleans, LA.

Summary: Sleep deprivation is known to adversely affect learning and memory. We examined the effects of sleep deprivation on attentional and memory processes in rats that received unilateral cholinergic lesions with 192IgG-saporin. Young Fisher 344 male rats were evaluated on an olfactory discrimination learning task both before and after exposure to 8 hours of sleep deprivation. Prior to testing, rats were trained to associate a particular scent with a food reward. They were then tested on their ability to successfully distinguish between two randomly placed, differently scented cups to retrieve the food reward. On a second experiment we investigated the effect that chronic estrogen administration may exert on the cognitive response to sleep deprivation. Gonadectomized rats were implanted s.c. with a pellet containing estrogen or placebo, and tested before and after sleep deprivation, one month after treatment. Untreated rats displayed impaired performance on the retention of the olfactory discrimination task; sleep deprivation resulted in an inability to remember the association of the baited scent from the previous day of testing. However, hormonal treatment appeared to have no significant effect on olfactory discrimination performance. These findings suggest a beneficial effect of sleep in learning and memory. Further research is needed to unravel the role of steroid hormones in modulating sleep-deprived learning deficits in rodents.

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

Lee R, Gallegos RA, Crawford EF, Wills DN, Zhukov VI, Huitron-Resendiz S, Criado JR, Henriksen SJ (2003) Ventral tegmental area lesions alter EEG power spectrum across the sleep/wake cycle. Neuroscience 2003 Abstracts 616.5. Society for Neuroscience, New Orleans, LA.

Summary: The ventral tegmental area (VTA) has long been implicated in reward and drug abuse. We previously demonstrated (Lee et al, J. Neurosci. 2001) a role for VTA GABAergic neurotransmission in REM sleep. In continuing studies the potential role of the VTA in modulating electroencephalogram (EEG) activation was explored by selectively lesioning mu-opioid receptor expressing cells, or NMDA-lesioning cells, in the VTA. Under sodium pentobarbital anesthesia rats received either (1) a sham operation (2) a saporin injection (3) an injection of a dermorphin-saporin (DERM-SAP) conjugate (Advanced Targeting Systems, San Diego, CA) (4) or a bilateral VTA injection of NMDA. All injections were delivered in a volume of 0.5 to 1.0 µL over 4 to 8 minutes. Animals were also implanted with electrodes for recording the EEG & EMG. The filtered EEG & EMG were recorded continuously for 24 hours beginning 21 days after surgery. Frequency analysis of the EEG in 15-sec epochs revealed differences in the distribution of relative power in the DERM-SAP or NMDA-lesioned animals, compared to controls. Higher frequency components (12-25 Hz) were reduced in DERM-SAP lesioned animals during waking and slow wave sleep. Histology demonstrated gliosis of GAD-stained neurons in the VTA 3 to 4 weeks after injection of DERM-SAP. These data suggest that long-projecting GABA neurons of the VTA have a desynchronizing influence on cortical EEG arousal mechanisms. This is supported by anatomical evidence of both direct and indirect non-thalamic GABAergic projections to widespread areas of cortex in the rodent. Supported by: DA08301 to SJH.

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

Reynolds JN, Sutherland JM, Sutherland RJ (2003) A novel nitrate ester enhances performance in a spatial memory task in rats with forebrain cholinergic depletion. Neuroscience 2003 Abstracts 626.11. Society for Neuroscience, New Orleans, LA.

Summary: Forebrain acetylcholine (ACh) depletion is associated with a variety of cognitive problems, including memory deficits. Here we evaluate the efficacy of a novel nitrate ester, GT 1061, a potential cognition enhancer, in reversing the memory deficit produced by ACh depletion. Long-Evans hooded rats were stereotaxically injected with 192-IgG-saporin intraventricularly or into basal forebrain cell regions to effect loss of cholinergic cells in the basal forebrain and depletion of cholinergic input to neocortex and hippocampus. The rats were postoperatively tested in a version of the Morris water task in which the location of the hidden platform was changed every second day. This version allows for repeated testing of new spatial learning and 24-hr memory retention. ACh depletion causes statistically reliable deficits in new learning and retention components of the task. We examined the effects of oral (0.5, 1, 5, and 10 mg/kg) and intraperitoneally injected (1, 10, 25 and 50 mg/kg) GT 1061 and donepezil oral (0.05, 0.5, 0.1, 1 mg/kg) and intraperitoneal (0.5 mg/kg) on performance of ACh depleted rats. Both oral and injected GT1061 (10 mg/kg oral, and 1 mg/kg i.p.) and donepezil improved new learning and retention performance. The improvement was especially evident during the 24-hr retention tests when GT1061 treated rats performed as well as normal rats. On this measure 10 mg/kg GT 1061 and 1 mg/kg donepezil administered orally were equipotent.

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

Dudkin KN, Chueva IV, Makarov FN, Beach TG, Roher AE (2003) Impairments of working memory processes on a model of Alzheimer’s disease in monkeys. Neuroscience 2003 Abstracts 626.8. Society for Neuroscience, New Orleans, LA.

Summary: We have investigated the characteristics of visual working memory in a delayed-discrimination task in a model of Alzheimer’s disease (AD) in rhesus monkeys. Three animals received unilateral stereotaxic intracerebroventricular injection of the nucleus basalis of Meynert and three monkeys received sterile saline injections and thus served as controls. The lesioning agent consisted of a ribosomal toxin, saporin, conjugated to monoclonal antibodies against (the nbM lesion) the p75 neurotrophin receptor (p75NTR), which is expressed almost exclusively on cholinergic neurons of the nbM. The rationale for the model is the same as for a rabbit model of AD (Roher et al, Ann. NY Acad Sci. 2000). The monkeys were trained to discriminate stimuli with different types of visual information (spatial frequency gratings, color, spatial choice, spatial relationships between components of objects). The data obtained demonstrate that the nbM lesioning agent had a weak effect on visual differentiation without delay (long-term memory), but significantly decreased the duration of information storage (by a factor of 2 – 3) in working memory later two months after injection. These changes depended on temporal stage after injection and stimulus properties, and were accompanied by increase of motor reaction time and of refusal of task decision. In monkeys that were sham injected, there were no alterations in working memory characteristics. The results suggest that considerable worsening of the working memory characteristics for monkeys after lesion of the nbM reflects the formation of an AD model in these monkeys. The principles of functional organization of working memory and role of pathology of the cortical mechanisms in an impairment of memory characteristics are discussed.

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Kim I, Wilson RE, Wellman CL (2003) Cholinergic deafferentation increases expression of the glur-1 subunit of the AMPA receptor in frontal cortex of young adult but not aging rats. Neuroscience 2003 Abstracts 633.9. Society for Neuroscience, New Orleans, LA.

Summary: Previously, we demonstrated that plasticity of frontal cortex is altered in aging rats: cholinergic lesions of the nucleus basalis magnocellularis (NBM) produce larger declines in dendritic morphology in frontal cortex of aged rats compared to young adults. In addition, these lesions result in upregulation of dendritic spines in frontal cortex of young adult but not aging rats. To begin to identify possible mechanisms underlying age-related differences in plasticity after NBM lesion, we assessed immunohistochemical labeling of the AMPA receptor subunit GluR1 in young adult and aging rats after either sham or 192 IgG saporin lesions of the NBM. Young adult (N=17), middle-aged (N=16), and aged rats (N=13) received unilateral sham or 192 IgG saporin lesions of the NBM. Two weeks later, brains were processed for immunohistochemical labeling of the GluR1 subunit of the AMPA receptor. An unbiased stereological technique was used to estimate density of labeled neurons in layer II-III of frontal cortex. Cells were identified as neurons based on standard morphological criteria and counted. Using a computerized image analysis system interfaced with a microscope, the average optical density of the white matter below frontal cortex was determined; neurons with optical densities at least one standard deviation above this mean were identified as intensely labeled. In young adult rats, lesions produced a 55% increase in the density of intensely GluR1-immunopositive neurons in frontal cortex. On the other hand, lesions had no effect on counts of GluR1-immunoreactive neurons in middle-aged and aged rats. This age-related difference in lesion-induced expression of AMPA receptor subunit protein could underlie the age-related differences in dendritic plasticity after NBM lesions.

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

Janssen WG, Andrews G, Tomey MI, Baxter MG, Morrison JH (2003) Combined bilateral perforant path lesions with lesions of the cholinergic system: an ultrastructural immunogold analysis of nmdar1 representation within the dentate gyrus. Neuroscience 2003 Abstracts 676.26. Society for Neuroscience, New Orleans, LA.

Summary: Alzheimer’s disease is characterized by deterioration of cholinergic input to the hippocampus, as well as degeneration of input from the entorhinal cortex to the dentate gyrus(DG). Studies have demonstrated an upregulation of the NMDA receptor subunit, NR1, following unilateral ablatement of the perforant path(pp). We hypothesized that cholinergic innervation might be essential for DG plasticity following pp ablation. Our study was designed to investigate the synaptic distribution of NR1 following combined 192 IgG-Saporin lesions of the medial septum/vertical diagonal band(MS/VDB) and bilateral(bilat) pp knife cut ablation. Animals received bilat-pp lesions 2-3 weeks days post MS/VDB and were sacrificed 17 days following pp lesion. Four groups of rats were tested: 1)MS-VDB with sham bilat-pp; 2)sham MS-VDB with bilat-pp; 3)MS-VDB with bilat-pp; 4)sham MS-VDB with sham bilat-pp. Using postembedding immunogold electron microscopy and SynBin, a program designed for quantification and compartmentalization of immunogold particles at the synaptic level, we investigated these effects in the outer molecular layer of the DG in a pilot study with 2 animals/group. Initial results suggest that the synaptic pools of NR1 within post-synaptic compartments were not affected with single MS/VDB, but that a long term synaptic down regulation of NR1 follows bilat pp lesion that is not affected by the additional removal of cholinergic input. While these combined lesions do not alter the pattern of synaptic NR1 receptor distribution following pp lesions, these data has important implications for lesion-induced hippocampal plasticity as well as structural and functional recovery.

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