targeted-toxins

Q: We have a question about two 192-IgG-SAP (Cat. #IT-01) lots. According to your data sheet there is an approximate 4-fold difference in ED50 between your new lot and old lot. We also observed a clear difference in behavior between animals dosed with the new batch and the old one. It is thus obvious that the new lot needs to be diluted to achieve the same results, however, we are uncertain if this can be calculated just based on the ED50 values. Do you have any experience about dose-responses with the different lots in terms of size of lesion?

A: We don’t have an exact correlation between in vitro and in vivo activity, unfortunately. We state on the data sheet to check a new batch on a small number of animals.

“There may be lot-to-lot variation in material; working dilutions must be determined by end user. If this is a new lot, you must assess the proper working dilution before beginning a full experimental protocol.”

Related: Targeted Toxins

Li AJ, Wang Q, Dinh TT, Ritter S (2010) Featured Article: Deletion of NPY/AGRP and POMC neurons in the arcuate nucleus by leptin-saporin produces hyperphagia, obesity and changes in diurnal feeding patterns in rats. Targeting Trends 11(1)

Related Products: Leptin-SAP (Cat. #IT-47), Blank-SAP (Cat. #IT-21)

Read the featured article in Targeting Trends.

See Also:

• Li A-J et al. Leptin-saporin injection into the arcuate nucleus lesions NPY/AGRP and POMC neurons and produces hyperphagia, obesity and changes in diurnal feeding patterns in rats. Neuroscience 2009 Abstracts 374.5/EE116, 2009. Society for Neuroscience, Chicago, IL

Thomsen MS, Hay-Schmidt A, Hansen HH, Mikkelsen JD (2010) Distinct neural pathways mediate alpha7 nicotinic acetylcholine receptor-dependent activation of the forebrain. Cereb Cortex 20(9):2092-2102. doi: 10.1093/cercor/bhp283

Summary: a7 nicotinic acetylcholine receptor (nAChR) agonists are potential treatments for some aspect of schizophrenia. The authors examine whether cholinergic neurons in the horizontal limb of the diagonal band of Broca (HDB) are a target for this treatment. Rats received 300 ng injections of 192-IgG-SAP (Cat. #IT-01) into the HDB. The results demonstrate that cholinergic neurons in the HDB are essential for a7 nAChR agonist activation of the medial prefrontal cortex.

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

Gibbs RB (2010) Estrogen therapy and cognition: a review of the cholinergic hypothesis. Endocr Rev 31(2):224-253. doi: 10.1210/er.2009-0036

Summary: This review discusses estrogen therapy for use in postmenopausal women. In this context the issues revolve around benefits vs. harm of such therapy on the brain and cognitive impairment associated with aging and Alzheimer’s disease. Use of 192-IgG-SAP (Cat. #IT-01) to investigate this paradigm is described.

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

Robertson RT, Baratta J, Yu J, LaFerla FM (2009) Amyloid-beta expression in retrosplenial cortex of triple transgenic mice: relationship to cholinergic axonal afferents from medial septum. Neuroscience 164:1334-1346. doi: 10.1016/j.neuroscience.2009.09.024

Summary: In this work the authors developed a model to examine the relationship between afferent projections and the formation of amyloid-beta (Aβ) deposits. Mice received 1.86 µg unilateral injections of 192-IgG-SAP (Cat. #IT-01) into the lateral ventricle. Lesioned animals had persistent Aβ immunoreactivity in layer III of the granular division of retrosplenial cortex (RSg). This data indicates that septal cholinergic axonal projections transport Aβ or amyloid precursor protein to layer III of the RSg.

Related Products: 192-IgG-SAP (Cat. #IT-01), mu p75-SAP (Cat. #IT-16)

Wilson RE, Coons KD, Sengelaub DR (2009) Neuroprotective effects of testosterone on dendritic morphology following partial motoneuron depletion: efficacy in female rats. Neurosci Lett 465:123-127. doi: 10.1016/j.neulet.2009.09.007

Summary: Previous work has demonstrated a protective effect from testosterone in a motoneuron nerve injury model for male rats. This work investigated whether testosterone has the same effect in females. Female rats received 2 µg of CTB-SAP (Cat. #IT-14) into the left vastus medialis muscle. 4 weeks later surviving motoneurons were visualized with CTB conjugated to HRP. Testosterone treatment greatly attenuated the atrophy seen in control animals, suggesting that testosterone is also a neurotherapeutic agent in females.

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Carter ES, Newman LA, Mcgaughy J (2009) Effect of aging and prefrontal cholinergic deafferentation on working memory for familiar and novel odors. Neuroscience 2009 Abstracts 879.14/EE124. Society for Neuroscience, Chicago, IL.

Summary: Aging is associated with cholinergic fiber loss in the entorhinal cortex (EC). Previous research has shown that acetylcholine (ACh) in this region mediates memory for novel information (Schon et al., 2005), and cholinergic lesions of the EC in young rats impair memory for novel, but not familiar, stimuli at an odor delayed non-match to sample task (DNMS; McGaughy et al., 2005). Currently, we tested whether age-related cholinergic fiber loss in the medial EC of male rats would be sufficient to produce impairments in memory for novel information during the DNMS task. Half of the aged animals were subjected to cholinergic depletion of medial, prefrontal cortex (pACh-lx) including both prelimbic and anterior cingulate cortex prior to the onset of testing. We hypothesized that this previous damage would result in impairments in memory for familiar items and would prevent improvements in memory shown after repeated exposure to novel items. Additionally the effects of increasing the delay between sample and choice portions of the test and memory for list of items were assessed. The pACh-lx animals were not impaired relative to sham-lx animals at memory for familiar information when there was a minimal delay between the sample and choice. However if a 15 minute delay was introduced between the sample and choice phase, pACh-lx rats performed more poorly than sham-lx rats. This suggests that ACh in the medial, prefrontal cortex is necessary for maintaining representations of familiar stimuli over a delay period. Aged rats showed accuracy impairments during sessions that required encoding of novel samples relative to their own performance at sessions requiring encoding of familiar samples. This impairment was greater on trials that required rats to discriminate the novel sample from a familiar non-match than on trials where all stimuli were novel. Though the extent of cholinergic fiber loss in EC due to aging was highly similar to that produced by infusion of the 192 IgG saporin to the EC of young rats, the severity of the cognitive impairments due to aging was not as great as that produced by lesioning. These data suggest that impact of damage to the cholinergic fibers of EC may vary based on whether the deterioration is gradual or has an acute onset.

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

Bailey AM, Enos J, Medley V (2009) Damage to nucleus basalis magnocellularis (nBM) cholinergic target areas produce different effects on the acquisition of learning set. Neuroscience 2009 Abstracts 879.15/EE125. Society for Neuroscience, Chicago, IL.

Summary: Lesions to the nucleus basalis magnocellularis (nBM) using either quisqualic acid or 192 IgG-saporin produce differing effects on the acquisition of learning set. Specifically, quisqualic acid lesions produce severe and long lasting impairments but 192 IgG-saporin lesions produce transient effects on learning set acquisition. One possible explanation for acquisition differences involves altered neuronal activity in the cholinergic target areas of the nBM. We examined two main cholinergic targets of the nBM, namely the amygdala and the prefrontal cortex (PFC). Rats with either NMDA (20 µg/µl) lesions to the basolateral amygdala (n=10) or NMDA (20 µg/µl) lesions to the anterior cingulate PFC (n=6) were tested on an olfactory learning set formation task as well as operant delayed non-matching to-position (DNMTP) and open field activity. The rats with amygdala lesions were additionally tested on a fear conditioning task. Lesions to the PFC significantly impaired acquisition of learning set as measured by chance performance on Trial 2 (M = 56.17%, SD = 7.47). Rats with PFC lesions did not differ from sham animals on the DNMTP task (p > .05) or in activity counts in an open field (p > .05). However, rats with NMDA lesions to the amygdala were significantly higher than chance (50% correct) on Trial 2 (p .05) or percentage correct on the DNMTP task (p > .05). NMDA lesions to the amygdala did, however, significantly decrease time spent freezing to an aversive CS+ in the fear conditioning task (p < .05). In total, the results imply that learning set acquisition differences following either quisqualic acid or 192 IgG-saporin lesions to the nBM are not likely due to damage to the cholinergic projection to the amygdala but may be associated with altered PFC activity.

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

Rennie KE, Ward C, Fréchette M, Pappas BA (2009) Effects of combined neonatal cholinergic lesion and chronic cerebral hypoperfusion on CA1 cytoarchitecture. Neuroscience 2009 Abstracts 736.23/M38. Society for Neuroscience, Chicago, IL.

Summary: Neonatal lesioning of the basal forebrain cholinergic (BFC) system alters cytoarchitecture of pyramidal cells in both the hippocampus and neocortex of the adult rat, indicating a role for the BFC in forebrain development. In addition to altering forebrain development, neonatal cholinergic lesion may also exacerbate the brain’s response to pathological factors that emerge as the brain ages. One factor that might interact with BFC lesion is reduced cerebral blood flow (hypoperfusion). Examining this interaction is especially interesting because both BFC degeneration and reduced cerebral blood flow are characteristics of Alzheimer’s disease. In the rat, chronic cerebrovascular insufficiency by itself reportedly causes the degeneration of hippocampal CA1 pyramidal cells, alters amyloid processing and produces spatial memory impairments. We hypothesized that neonatal cholinergic lesion using the cholinotoxin 192-IgG-saporin would render the hippocampus more vulnerable to the neuropathological effects of chronic forebrain hypoperfusion induced by permanent bilateral occlusion of the carotid arteries (2VO). We previously reported that combined BFC lesion and 2VO impaired working memory in the Morris water maze and increased anxiety-like behaviours on the elevated plus apparatus, whereas neither of these treatments alone caused any of these effects. Here we report the effects of neonatal BFC lesion, 2VO, or their combined application on hippocampal CA1 cytoarchitecture using quantitative Golgi analysis. Rats subjected to 2VO showed increased apical branch length and spines, and increased basal spines. Neonatal BFC lesion on its own had only restricted effects on apical branch length at certain branch orders and no effect on spines. However, at a number of branch orders the stimulating effect of 2VO on apical spines occurred only in animals subjected to neonatal BFC lesion, indicating that this lesion modulated the response to 2VO. To our knowledge, this is the first examination of the effects of 2VO on CA1 neuron cytoarchitecture. Surprisingly, it increased rather than decreased dendritic length and spines. Furthermore, while the BFC lesion had minimal effects on its own, it was permissive to some of the effects of 2VO on dendritic spines. Taken together with our previous data, this study suggests that pre-existing cholinergic dysfunction alters aspects of both the behavioural and neural consequences of chronic hypoperfusion. These results may have implications for Alzheimer’s disease where cholinergic dysfunction and hypoperfusion are co-expressed

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Coons KD, Munoz F, Osborne MC, Sengelaub DR (2009) Dendritic atrophy following partial motoneuron depletion: Time course of recovery and protection with androgens and estrogens. Neuroscience 2009 Abstracts 743.2/R17. Society for Neuroscience, Chicago, IL.

Summary: We have previously demonstrated that partial depletion of motoneurons innervating the quadriceps muscles induces dendritic atrophy and loss of function in remaining motoneurons. Furthermore, treatment with testosterone is neuroprotective, and dendritic atrophy and loss of function following partial motoneuron depletion are attenuated in a dose-dependent fashion, and in both male and female rats. In the present study, we assessed dendritic atrophy after partial motoneuron depletion at a variety of time points to determine its time course and pattern with and without testosterone treatment. We also examined the potential neuroprotective effects of the androgenic and estrogenic metabolites of testosterone. Motoneurons innervating the vastus medialis muscle were selectively killed by intramuscular injection of cholera toxin-conjugated saporin. Simultaneously, saporin-injected males were given implants containing either testosterone (45mm), dihydrotestosterone (30mm), estradiol (10%, 10mm), or left untreated. At 2, 4, 6, or 10 weeks after partial motoneuron depletion, motoneurons innervating the ipsilateral vastus lateralis muscle were labeled with cholera toxin-conjugated HRP, and dendritic arbors were reconstructed in 3 dimensions. Animals treated with dihydrotestosterone or estradiol were assessed only at 4 weeks post depletion. Dendritic arbors were also assessed in a group of untreated normal males. Quadriceps motoneuron dendrites underwent a rapid atrophy and protracted recovery following partial motoneuron depletion. Dendritic atrophy in remaining quadriceps motoneurons was apparent at 2 weeks after motoneuron depletion, with a decrease of over 50% in dendritic length, and this atrophy remained through 6 weeks post-depletion; dendritic length recovered by 10 weeks post-depletion. Treatment with testosterone attenuated induced dendritic atrophy at all time points, and recovery to normal lengths was present at 6 weeks post-depletion. Treatment with dihydrotestosterone or estradiol was as effective as testosterone in attenuating dendritic atrophy in remaining quadriceps motoneurons. These results suggest that treatment with testosterone is neuroprotective, both attenuating induced dendritic atrophy and accelerating recovery. Furthermore, this effect can be achieved with both androgenic and estrogenic metabolites, further supporting a role for hormones as neurotherapeutic agents in the injured nervous system.

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