targeted-toxins

Harrell LE, Parsons D, Kolasa K (2001) Hippocampal sympathetic ingrowth occurs following 192-IgG-saporin administration. Brain Res 911:158-162. doi: 10.1016/s0006-8993(01)02626-9

Summary: Electrolytic lesions of the medial septal region in rats cause peripheral sympathetic fibers from the superior cervical ganglia to grow into the cholinergically-denervated areas of the hippocampus. This lesioning method is non-specific and disrupts several other cell types in the area of the lesion. The authors infused 192-Saporin (1 µg/10 µl saline into medial septum; Cat. #IT-01) to eliminate only the cholinergic neurons, leaving other cell types intact. Hippocampal sympathetic ingrowth still occurs when only the cholinergic neurons are eliminated, indicating that this occurrence is in response to the loss of cholinergic projections from the medial septum.

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

Burk JA, Sarter M (2001) Dissociation between the attentional functions mediated via basal forebrain cholinergic and GABAergic neurons. Neuroscience 105(4):899-909. doi: 10.1016/s0306-4522(01)00233-0

Summary: The specificity and efficacy of 192-Saporin (Cat. #IT-01) has allowed the extensive investigation of cortical cholinergic inputs in attentional functions. Little is known about the function of non-cholinergic neurons because of the lack of a specific tool to eliminate these projections. The authors injected 192-Saporin (0.1 µg/0.5 µl bilateral infusions) into rats and compared performance to rats treated with ibotenic acid to eliminate GABAergic neurons in attention performance tasks. While the ibotenic acid lesions were not as specific as those produced by 192-Saporin, the data suggest a role for the basal forebrain GABAergic neurons in attentional functions.

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

Daniels D, Miselis RR, Flanagan-Cato LM (2001) Transneuronal tracing from sympathectomized lumbar epaxial muscle in female rats. J Neurobiol 48(4):278-290. doi: 10.1002/neu.1057

Summary: The authors use pseudorabies virus (PRV) to study central neural networks such as the one controlling the lordosis reflex (increased curvature of the spine). To aid in the separation of the sympathetic nervous system and higher order systems, rats were treated with lumbar injections of anti-DBH-SAP (156 ng to 5 µg; Cat. #IT-03), then labeled with PRV. PRV labeling in the brain was absent in areas associated with vasomotor tone, but persisted in areas implicated in control of the lordosis response.

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

Linster C, Garcia PA, Hasselmo ME, Baxter MG (2001) Selective loss of cholinergic neurons projecting to the olfactory system increases perceptual generalization between similar, but not dissimilar, odorants. Behav Neurosci 115(4):826-833. doi: 10.1037//0735-7044.115.4.826

Summary: Selective cholinergic lesioning of the basal forebrain has been linked to attentional and cognitive deficits. 192-Saporin (Cat. #IT-01) was administered to the horizontal limb of the diagonal band of Broca (0.3 µl at 0.175 µg/µl in each hemisphere) destroying projections to the olfactory bulb and cortex. The results demonstrate cholinergic lesions affect the perceptual qualities of odors, and may possibly represent a general mechanism for cholinergic effects on information processing.

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

Gray PA, Janczewski WA, Mellen N, McCrimmon DR, Feldman JL (2001) Normal breathing requires preBotzinger complex neurokinin-1 receptor-expressing neurons. Nat Neurosci 4(9):927-930. doi: 10.1038/nn0901-927

Summary: SP-SAP was effective in eliminating preBötC NK1R neurons in adult rats. Unilateral SP-SAP injection transiently produced sighs (large inspiratory efforts followed by prolonged expiration).

Usage: Injections of 0.1–0.2 pmol of SP-SAP or 0.3 pmol each of unconjugated Saporin and Substance P were made in the pre-BötC.

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

Motooka Y, Kondoh T, Nomura T, Tamaki N, Tozaki H, Kanno T, Nishizaki T (2001) Selective cholinergic denervation inhibits expression of long-term potentiation in the adult but not infant rat hippocampus. Devel Brain Res 129:119-123. doi: 10.1016/s0165-3806(01)00179-1

Summary: The authors studied the possible role of cholinergic systems in long-term potentiation (LTP), which is one of the most intensively studied models of learning and memory. 192-Saporin (4.2 µg/5 µl, Cat. #IT-01) injections were made in both infant and adult rats and the probability of LTP development was studied in hippocampal slices from animals treated 2 weeks or 2 months before. Cholinergic denervation by 192-Saporin did not affect LTP expression in the infant brain, however, the results strongly suggest that cholinergic systems in the adult brain participate in an LTP pathway.

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

Porreca F, Burgess SE, Gardell LR, Vanderah TW, Malan TP Jr, Ossipov MH, Lappi DA, Lai J (2001) Inhibition of neuropathic pain by selective ablation of brainstem medullary cells expressing the µ-opioid receptor. J Neurosci 21(14):5281-5288. doi: 10.1523/JNEUROSCI.21-14-05281.2001

Summary: The presence of descending projections in the pain pathway raises the possibility that abnormal sustained activity may perpetuate chronic pain. Using 3-ng injections of dermorphin-SAP (Cat #IT-12) on either side of the RVM in rats the authors both prevented and reversed neuropathic pain caused by spinal nerve ligation.

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

Q: What are the options for delivery of targeted toxins?

A: The options for toxin delivery are varied and limited only by investigator ingenuity. Generally, injection has been the route of choice. Some toxins can be given intravenously, such as 192-Saporin (192-IgG-SAP, Cat. # IT-01) or anti-DBH-SAP (Cat. # IT-03), in which case all cells expressing p75 or dopamine beta-hydroxylase and exposed to the systemic circulation are potential targets. Intravenous injections will not deliver toxins to the CNS.

Subarachnoid injections have been used successfully for immunotoxins and peptide toxins such as SP-SAP (Cat. # IT-07).

Direct intraparenchymal injections have been used to restrict toxin application to just a few target cells. However, intraparenchymal injections require careful attention to injection technique and are impractical for large target structures.

Q: When injecting directly into tissue, are there any special techniques that should be used?

A: Direct injections into brain or spinal cord have been used successfully by some investigators. Specifics of toxin dose, concentration, injection volume and speed of injection have varied considerably. If a high concentration of toxin is deposited locally, lesion specificity is often lost. Presumably, if toxin concentration is too high, cellular uptake by non-specific bulk fluid-phase endocytosis (pinocytosis) can internalize enough saporin to be lethal.

There is currently interest in “convective” delivery techniques developed in the laboratory of Dr. Edward Oldfield at the NIH. The basic principle is to deliver a relatively large concentration slowly over an extended period, often using a rather dilute solution. The parameters for any given species and injection site need to be determined by pilot experiments.

Q: What sort of special care should be given to the animal after administration of the targeted toxin?

A: The toxins generally bind and internalize within minutes, although some immunotoxins circulate for longer periods if injected intravenously. However, no significant amount of active toxin is excreted. So, animals can be returned to group housing immediately after toxin injection. The only special requirements may derive from the specific target being studied. For example, rats given intraventricular 192-Saporin (192-IgG-SAP, Cat. # IT-01) develop decreased fluid and food intake for several days after injection. Since the adipsia is significant, providing the animals with fresh, juicy vegetables, such as cucumber or potatoes, can help.

Rats injected intraventricularly with anti-DBH-SAP (Cat. # IT-03) will lose considerable body weight and are slow to regain. They, too, may benefit from food supplements, including nuts and other high calorie appetizing treats. Otherwise, common sense care of any neurologic deficits is indicated depending on the target and toxin being used.

See: Targeted Toxins

Lappi DA (2001) Featured Article: Dermorphin-SAP kills MOR-positive cells. Targeting Trends 2(3)

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

Read the featured article in Targeting Trends.

Browne SE, Lin L, Mattsson A, Georgievska B, Isacson O (2001) Selective antibody-induced cholinergic cell and synapse loss produce sustained hippocampal and cortical hypometabolism with correlated cognitive deficits. Exp Neurol 170:36-47. doi: 10.1006/exnr.2001.7700

Summary: The authors used 192-Saporin (two 2.5-µg bilateral injections of 1 µg/µl; Cat. #IT-01) to eliminate cholinergic neurons in the rat, then measured cerebral rates of glucose utilization. The findings show sustained reduction in glucose utilization in the brain regions showing loss of cholinergic neurons, specifically the frontal cortical and hippocampal regions. These same animals demonstrated impaired performance in a Morris water maze. The results reinforce the theory that cholinergic systems influence metabolism and cognition in the cortex and hippocampus.

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