targeted-toxins

Chudasama Y, Dalley JW, Nathwani F, Bouger P, Robbins TW (2004) Cholinergic modulation of visual attention and working memory: Dissociable effects of basal forebrain 192-IgG-saporin lesions and intraprefrontal infusions of scopolamine. Learn Mem 11(1):78-86. doi: 10.1101/lm.70904

Summary: It is hypothesized that cortical cholinergic dysfunction underlies the cognitive impairments associated with dementia and normal aging. The authors examined the role of these neurons in both attentional and mnemonic functions, using either bilateral infusions of 125 ng of 192-Saporin (Cat. #IT-01) into the bregma of rats or infusions of scopolamine. The results suggest that attentional and working memory capacities can be tested separately during the same session. It is also indicated that the CBF system is a modulator of both attentional and mnemonic processing.

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

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. Exp Neurol 184(2):1010-1016. doi: 10.1016/S0014-4886(03)00388-1

Summary: Narcolepsy has recently been shown to be a neurodegenerative disease. Data from several different sources indicate that narcoleptics have very low levels of hypocretin (HCRT)-containing neurons. The authors sought to verify a direct linkage between HCRT-containing neurons and HCRT levels in the CSF. Rats were lesioned with 45-90 ng of orexin-SAP (Cat. #IT-20) bilaterally into the lateral hypothalamus. Loss of HCRT neurons correlated with decreased levels of HCRT in the CSF.

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

Janisiewicz AM, Baxter MG (2003) Transfer effects and conditional learning in rats with selective lesions of medial septal/diagonal band cholinergic neurons. Behav Neurosci 117(6):1342-1352. doi: 10.1037/0735-7044.117.6.1342

Summary: Conditional learning appears to require cholinergic input to the hippocampus and cingulate cortex. Using a total of 0.5 µl of 0.12 µg/µl 192-Saporin (Cat. #IT-01) injected into the medial septal area of rats, the authors investigated the role of cholinergic input in conditional learning. The results suggest that cholinergic neurons of the medial septum/vertical limb of the diagonal band play a role in the transfer of behavioral experience rather than in conditional learning itself.

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

Harmon KM, Wellman CL (2003) Differential effects of cholinergic lesions on dendritic spines in frontal cortex of young adult and aging rats. Brain Res 992:60-68. doi: 10.1016/j.brainres.2003.08.029

Summary: The authors used 0.15 µg of 192-Saporin (Cat. #IT-01) injected into the nucleus basalis magnocellularis of rats to study whether dendritic spine density is altered by cholinergic deafferentation. While the spine density decreased in young rats, middle-aged and aged animals did not display a density significantly different than controls.

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

Vuckovich JA, Semel ME, Baxter MG (2004) Extensive lesions of cholinergic basal forebrain neurons do not impair spatial working memory. Learn Mem 11:87-94. doi: 10.1101/lm.63504

Summary: The authors wished to examine whether cerebellar Purkinje cells damaged during a cholinergic basal forebrain lesion might be the cause of impaired working memory. Four injections of 0.2-0.3 µl (0.12-0.15 µg/ml, 192-Saporin, Cat. #IT-01) into the medial septum/vertical limb of the diagonal band, two injections into the horizontal limb of the diagonal band of Broca, and four injections into the nucleus basalis magnocellularis/ substantia innominata of rats were used to produce a very specific lesion. The results indicate that the cholinergic basal forebrain does not play a substantial role in spatial working memory.

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

Farhadi HF, Lepage P, Forghani R, Friedman HC, Orfali W, Jasmin L, Miller W, Hudson TJ, Peterson AC (2003) A combinatorial network of evolutionarily conserved myelin basic protein regulatory sequences confers distinct glial-specific phenotypes. J Neurosci 23(32):10214-10223. doi: 10.1523/JNEUROSCI.23-32-10214.2003

Summary: The authors used intrathecal injections of 0.3 µg CTB-SAP (Cat. #IT-14) to induce spinal cord demyelination for the purpose of defining the regulatory network controlling myelin basic protein transcription in mice.

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

Pokala VN, Witt-Enderby PA, Johnson DA (2003) Effect of selective cholinergic lesion of the septohippocampal pathway on the carbachol stimulated GTPγS binding in rat hippocampus. Neuroscience 2003 Abstracts 799.7. Society for Neuroscience, New Orleans, LA.

Summary: Previously we have shown that selective lesion of the septohippocampal cholinergic pathway in the rat resulted in a significant decrease in hippocampal extracellular acetylcholine concentration and an increase in muscarinic receptor binding. The intent of this study was to investigate the effect of selective cholinergic lesion of the septohippocampal pathway on muscarinic receptor-coupled G protein activation. Measurement of agonist-stimulated GTP〔γ-35S〕 binding was used as a function of ligand-receptor interactions. Sprague-Dawley rats were infused into the medial septum with either the selective cholinergic immunotoxin 192 IgG-saporin (SAP) (0.22 μg in 1μl aCSF) or vehicle. After 6 weeks the rats were euthanized and the hippocampus dissected from the brain and quickly frozen. Hippocampal homogenate was analyzed for GTPγS binding following exposure to the muscarinic agonist carbachol (1 nM-10 mM). Data were analyzed to obtain EC50 of carbachol and Emax values for GTPγS binding using non-linear regression analysis. The results demonstrated, in control animals carbachol stimulated 35S GTPγS binding to be 150% over basal with an EC50 value of approximately 100 μM. However, in SAP lesioned animals no concentration dependent increase in 35S GTPγS binding occurred. Therefore, though we saw an increase in the muscarinic receptor binding at the hippocampus on SAP lesioning, these receptors seem to be nonfunctional.

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

Nattie EE, Li A (2003) Substance P-saporin lesions of NK1-receptor expressing neurons in the medullary raphe reduce central chemoreception in sleep and wakefulness. Neuroscience 2003 Abstracts 826.7. Society for Neuroscience, New Orleans, LA.

Summary: Breathing, especially in sleep, depends on a CO2-related drive that comes from central chemoreceptors. Many brainstem chemoreceptor sites contain NK1-receptor expressing neurons and cell specific killing of them at one site, the retrotrapezoid nucleus, by injection of substance P-saporin (SP-SAP)produces hypoventilation and reduced chemosensitivity (J. Physiol. 544.2: 603-616, 2002). Here we focus on the medullary raphe, a putative chemoreceptor site rich in NK1-receptor expressing neurons. We studied rats, instrumented with EEG and EMG electrodes for sleep determination, before and during the two weeks after placing two injections (0.1 pmole in 100 nl of SP-SAP) 1 mm apart in the medullary raphe. SP-SAP injections reduced the number of NK1 receptor expressing neurons by 53% compared to controls injected with IgG-SAP (P< 0.01, two-way ANOVA). Room air breathing was unaffected in sleep or wakefulness. The level of breathing during inhalation of 7% CO2 at 7 and 14 days was reduced by 13 and 22%, respectively, in NREM sleep (P < 0.01, two way ANOVA) and by 19 and 24%, respectively, in wakefulness (P < 0.01, two way ANOVA). Body temperature, resting metabolic rate, and sleep cycling were not significantly affected. These SP-SAP injections did not significantly reduce the number of medullary raphe serotonergic neurons as determined by TPOH immunoreactivity. We conclude that, as in the retrotrapezoid nucleus, NK1 receptor expressing neurons in the medullary raphe are involved in central chemoreception.

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

Dinh TT, I’Anson H, Ritter S (2003) Poster: Immunotoxic destruction of distinct catecholaminergic neuron populations disrupts the reproductive response to glucoprivation in female rats. Neuroscience 2003 Abstracts 827.13. Society for Neuroscience, New Orleans, LA.

Summary: Chronic glucoprivation suppresses estrous cyclicity in hamsters (Schneider et al. 1997) and rats (I’Anson et al. 2003). This suppression can be viewed as an adaptive glucoregulatory response since by delaying pregnancy, it conserves metabolic fuels for maternal survival. Our previous work shows that corticosterone, feeding and adrenal medullary responses to glucoprivation are controlled by hindbrain glucose sensing cells and require activation of ascending or descending catecholamine neurons. The glucoreceptors responsible for the delay of estrous also appear to be located in hindbrain, since fourth ventricular infusion of low 2-deoxy-D-glucose (2DG) doses suppresses pulsatile LH secretion in rats (Nagatani et al. 1996). Here we tested the involvement of catecholamine neurons in suppressing estrous cycles during chronic glucoprivation. We microinjected the retrogradely transported immunotoxin, anti-dopamine beta hydroxylase (dbh)-conjugated to saporin (DSAP), bilaterally into the paraventricular nucleus of the hypothalamus (PVH) of female rats to selectively destroy dbh-containing catecholamine neurons projecting to this area. Neither DSAP nor unconjugated saporin (SAP) control injections altered basal estrous cycle length. To assess effects of chronic 2DG, rats were injected with 2DG (200 mg/kg every 6 hr for 72 hr) beginning 24 hr after detection of estrous following two normal 4-5 day cycles. Chronic glucoprivation increased cycle length significantly in 7/8 SAP controls but in only 1/8 DSAP rats. Lesion effectiveness and selectivity were confirmed by immunohistochemistry. Thus, hindbrain catecholamine neurons with projections to the PVH are not required for estrous cyclicity when metabolic fuels are abundant, but are required for inhibition of reproductive function during chronic glucose deficit.

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

Zhang J, Speth RC, Simasko S, Ritter RC (2003) Hypothalamic injection of targeted toxin for cholecystokinin receptive neurons leads to increased 24 hour food intake and weight gain. Neuroscience 2003 Abstracts 830.3. Society for Neuroscience, New Orleans, LA.

Summary: Peptides conjugated to the ribosomal toxin, saporin, bind to their specific G-protein coupled receptors, and are internalized. Once internalized, saporin inactivates ribosomes, selectively killing the receptive cells. We are using cholecystokinin (CCK)-saporin to selectively destroy CCK receptive neurons that may participate in the control of food intake and body weight. We have demonstrated that CCK-saporin binds to CCK-A receptors (Approximate IC50, 3nM), and evokes an increase in cytosolic calcium, which is blocked by the CCK-A receptor antagonist, lorglumide. Thus CCK-saporin has properties that recommend it as a targeted toxin of CCK-receptive neurons. We injected CCK-saporin (138 nM in 500 nl) bilaterally into the medial hypothalamus, an area where CCK-A receptors are expressed. CCK-saporin did not change 24h chow intake or weight gain. However, when rats were fed high fat diet, CCK-saporin treated rats increased their 24h food intake and gained nearly twice the weight as control rats during 14 days on this diet. Following an overnight fast CCK-saporin injected rats ate significantly more high fat diet than controls during the first 30 min after return of food. Nonetheless, both the CCK-saporin injected rats and controls reduced their food intake in response to intraperitoneal CCK-8. Our results suggest that ventromedial hypothalamic CCK receptors participate in control of 24h food intake and body weight gain. Our results also suggest that CCK-saporin may be a valuable tool for investigating the participation of discrete populations of CCK-sensitive neurons in various physiological responses.

Related Products: CCK-SAP (Cat. #IT-31)