targeted-toxins

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)

Fitz NF, Gibbs RB, Johnson DA (2003) Arousal enhances delayed match to position T-maze performance independent of septo-hippocampal cholinergic projections. Neuroscience 2003 Abstracts 425.17. Society for Neuroscience, New Orleans, LA.

Summary: Infusion of the selective cholinergic immunotoxin, 192 IgG-saporin (SAP) into the medial septum (MS) of rats selectively lesions cholinergic neurons projecting to the hippocampus and impairs acquisition of a delayed matching to position (DMP) T-maze task. The intent of the present study was to determine if enhanced performance associated with arousal is dependent on septo-hippocampal cholinergic projections. Male Sprague-Dawley rats received MS infusions of SAP 0.22 µg in 1µl or vehicle. Fourteen days later, animals were trained on the DMP spatial memory task. SAP and control animals were randomized into an “arousal” group that was injected with saline (IP; 1 ml/Kg) 30 min before testing each day or a “non-arousal” group that was not. SAP lesions significantly impaired acquisition of the DMP task in both the arousal and non-arousal groups. Conversely, arousal significantly enhanced acquisition in both control and SAP lesioned rats. There was no significant interaction between the effects of cholinergic lesions and arousal. These results suggest that septo-hippocampal cholinergic projections are not engaged in enhanced spatial learning mediated by arousal.

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

Butt AE, Corley S, Cabrera S, Chavez C, Kitto M, Ochetti D, Renovato A, Salley T, Sarpong A (2003) 192 IgG-saporin lesions of the nucleus basalis magnocellularis in rats fail to disrupt acquisition or retention of differential reinforcement of low rate responding. Neuroscience 2003 Abstracts 425.5. Society for Neuroscience, New Orleans, LA.

Summary: The frontal cortex has been implicated in supporting timing behavior in tests of differential reinforcement of low rate responding (DRL) in rats. DRL performance is similarly influenced by anticholinergic drugs; scopolamine interferes with DRL performance by increasing the number of nonreinforced responses and thus decreasing DRL efficiency. Because the frontal cortex receives significant cholinergic input from the nucleus basalis magnocellularis (NBM) in rats, we hypothesized that NBM lesions would disrupt DRL performance in the current experiment. Male Long-Evans rats were placed first in a DRL 10 s schedule of reinforcement before advancing to a DRL 20 s schedule. Rats received 50 trials per day for 20 consecutive days on both DRL schedules. When rats reached stable performance, they received either bilateral 192 IgG-saporin lesions of the NBM or sham lesions. Upon recovery, rats were reintroduced to the DRL 20 s task for 10 days of post-operative testing. Finally, rats were tested using a novel delay interval in a DRL 30 s task. Testing continued for 10 additional days. Results showed that the NBM lesion group showed no significant change in either the total number of responses or in DRL efficiency (reinforced responses / total responses) between pre- and post-operative DRL 20 s testing. Subsequent acquisition in the DRL 30 s task was similarly not disrupted by NBM lesions. The effectiveness of the lesions was verified by acetylcholinesterase (AChE) staining, which showed pronounced depletion of cortical AChE with normal AChE-positive staining in the hippocampus and medial septal area. These data suggest that the NBM is not critically involved in either the acquisition or retention of DRL performance.

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

Fletcher BR, Baxter MG, Rapp PR, Shapiro ML (2003) 192-IgG saporin lesions of the medial septum and vertical diagonal band impair cognitive flexibility. Neuroscience 2003 Abstracts 425.8. Society for Neuroscience, New Orleans, LA.

Summary: Learning and memory remain largely intact following selective basal forebrain cholinergic lesions. By comparison, single unit recording studies have documented reliable effects of such lesions, including abnormally rigid hippocampal place fields when animals are confronted with changes in the configuration of the testing environment. The present experiment tested the prediction that cholinergic lesions of the basal forebrain would impair performance of tasks requiring cognitive flexibility. Rats received 192-IgG saporin or control vehicle injections into the medial septal nucleus and vertical diagonal band, and were tested on cued and spatial delayed match-to-place tasks in a radial arm water maze. Test sessions consisted of four sample trials in which animals searched for a cued or hidden escape platform located in a fixed position at the end of one arm (60 sec cutoff, inter-trial interval = 15 sec). A memory delay was imposed by returning rats to the home cage for a variable delay (15 sec. – 6 hrs), followed by two test trials. The lesion and control groups learned at similar rates in both versions of the task, and performed comparably on the critical test trials, independent of the length of the retention interval. However, lesioned rats were impaired during the transition from the cued to spatial variants of testing. Specifically, the lesion group made significantly more errors on an early sample trial in the spatial task, returning to the location that was previously correct during cued training. Pending histological confirmation of the extent and selectivity of the experimental lesions, this pattern of results suggests that damage to the basal forebrain cholinergic system spares spatial learning but impairs cognitive flexibility when task contingencies are changed.

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