FAQ

Q: Are all lots of 192-Saporin (192-IgG-SAP, Cat. #IT-01) the same?

A: There are variances from lot to lot, and Advanced Targeting Systems includes a cytotoxicity graph on the data sheet with each product comparing the current lot with previous lots. Chemicon International also sells immunotoxins, and used to distribute ATS products. However, since early 2002 (according to Chemicon) they have been outsourcing their 192-Saporin from an un-named laboratory. A lot obtained from Chemicon was tested under ATS quality control conditions (see graph) and was found to be significantly less active than any of the ATS lots.

Q: How do I find out the optimal dosage?

A: For each new lot and each new application of immunotoxin, it is recommended that the end user perform preliminary tests to ascertain the proper dosage. The material used and the method of administration are important aspects of each experiment that should be carefully considered prior to beginning a full-blown project.

Q: What happens if I use too much immunotoxin?

A: Customers who had used the Chemicon material and then ordered 192-Saporin from ATS have reported that they needed to reduce the dosage level with ATS product. The Chemicon material was not as potent. Higher doses of 192-Saporin, (as described in Leanza et al.) cause deficits in hindlimb coordination and support, and ataxia. So it is important to use less if you’ve switched from Chemicon’s material to the ATS 192-Saporin.

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

References

1. Leanza G et al. Selective lesioning of the basal forebrain cholinergic system by intraventriculr 192-IgG-saporin: behavioural, biochemical and stereological studies in the rat. Eur J Neurosci 7:329-343, 1995.

Q: When performing intraparenchymal injections of immunotoxin, what is the proper volume to use? Is it better to induce two half-portions per hemisphere or is a higher concentration better? At what concentration do you expect necrosis or inflammation?

A: There is no one answer to the question of injection volume. Practically speaking, we have observed that large or extended structures such as the entire cholinergic basal forebrain (CBF) of rats are difficult to ablate with one single injection of 192-Saporin (192-IgG-SAP, Cat. #IT-01). The best results were obtained with 3-5 separate 0.5-1.0 µl injections. For even larger targets such as the CBF in primates, other strategies may be necessary. Oldfield and co-workers have reported success in delivering cytotoxic chemotherapy to large volumes of brain using long, slow infusions of solutions containing a low concentration of toxin (convective delivery). This procedure delivers toxin by bulk fluid flow rather than diffusion and avoids high local toxin concentrations around the infusion catheter or pipette. High local concentrations of toxin may compromise selectivity and produce non-specific cytotoxicity. This can occur when neurons and glia take up toxic amounts of saporin by bulk fluid phase endocytosis, rather than receptor-mediated endocytosis. With direct intraparenchymal injections, local necrosis can occur with surprisingly small doses of toxin. For example, 60 ng of SP-SAP (Cat. #IT-07) or dermorphin-SAP (Cat. #IT-12) into the rat striatum injected in 1 µl typically produces some necrosis in the center of the injection site. With immunotoxins such as 192-Saporin (192-IgG-SAP) or Anti-DBH-SAP (Cat. #IT-03), 200 ng in 0.5 µl may barely produce a trace of local damage.

Q: We are interested in the anti-Thy-1 nephritis model in rats. I want to know the titer of OX7-SAP (Cat. #IT-02) and how much we have to expend for each rat to establish the model?

A: The “titer” of OX7-SAP is rather difficult to define. It is not known precisely how many molecules of this immunotoxin are necessary to kill a thymic-derived (Thy-1-expressing) lymphocyte in vivo. Also, since OX7-SAP kills Thy-1-expressing lymphocytes, it may prove difficult to induce Thy-1 nephritis with the immunotoxin. In humans, proteinuria was reported in clinical trials using immunotoxins for treatment of cancer, but we do not know of any comparable data in rats. Probably the only way to determine the appropriate dose would be a dose ranging study.

Q: I have been doing research with 192-Saporin (192-IgG-SAP, Cat. #IT-01) for 2-3 years now. I have read in the literature that animals with cholinergic lesions often get sick following surgery and require potatoes, apples, lettuce and saline injections. They may even stop eating or drinking all together. I have followed these practices in the past, but stopped when it didn’t seem to make a difference. (I use a very small insignificant dose that is not prone to make animals ill). This is the first death I have had even remotely possibly related to the toxin. In short, the animal lost 64 grams over a period of 2 weeks, and expired 1-2 days thereafter. I weighed her at death and she was 139 grams (91 gram difference from her initial surgery weight). The rats in our colony are fed and given water ad libitum. However, we think that she dehydrated. She was given the same dose (1.1 microliters) as all of the other rats in the experiment. I do have other rats that were given injections from the same lot that do not appear to be sick or losing weight. I’m not sure what you can do with this information, but I would be grateful for whatever help you can offer.

In large series of intraventricular injections of 192-Saporin (192-IgG-SAP), I have never encountered quite the same sequence of events you describe. Death after intracranial toxin injection can reflect several possible misadventures including but not limited to:

1. Contamination of toxin solution with endotoxin resulting in death without awakening from anesthesia (usually due to bacterial contamination from prolonged exposure of toxin solution to room temperature),

2. Fatal intracranial hemorrhage which may result in delayed death depending on location and volume of bleeding,

3. Intracranial abscess (extremely unusual) from injection of contaminated solution, or

4. Unrelated bacterial, viral or parasitic systemic disease.

Q: Another one of my 192-Saporin-treated (or 192-IgG-SAP, Cat. #IT-01) rats is having an adverse reaction, including paralysis of the lower extremities. She has lost 40 grams in the past 3-4 days. Could this be Purkinje cell damage; does that happen after five weeks?

A: Purkinje cell damage after intraventricular injection of 192-Saporin (192-IgG-SAP) typically is manifest not by hind limb paralysis but rather tremor (shaking) and ataxia (clumsiness, poor balance). At less than lethal doses, 192-Saporin (192-IgG-SAP) does not produce paraparesis. Something else is going on. Rats develop hind limb paralysis from a variety of toxic or metabolic systemic insults in addition to specific nervous system disorders. The presence of rapid weight loss suggests the rat is systemically ill rather than an effect of a sub-lethal dose of 192-Saporin (192-IgG-SAP).

Selected references on convective delivery of toxin to brain:

Nguyen TT, Pannu YS, Sung C, Dedrick RL, Walbridge S, Brechbiel MW, Garmestani K, Beitzel M, Yordanov AT, Oldfield EH (2003) Convective distribution of macromolecules in the primate brain demonstrated using computerized tomography and magnetic resonance imaging. J Neurosurg 98(3):584-590.

Morrison PF, Chen MY, Chadwick RS, Lonser RR, Oldfield EH (1999) Focal delivery during direct infusion to brain: role of flow rate, catheter diameter, and tissue mechanics. Am J Physiol 277(4 Pt 2):R1218-R1229.

Lonser RR, Corthesy ME, Morrison PF, Gogate N, Oldfield EH (1999) Convection-enhanced selective excitotoxic ablation of the neurons of the globus pallidus internus for treatment of Parkinsonism in nonhuman primates. J Neurosurg 91(2):294-302.

Wood JD, Lonser RR, Gogate N, Morrison PF, Oldfield EH (1999) Convective delivery of macromolecules into the naive and traumatized spinal cords of rats. J Neurosurg 90(1 Suppl):115-120.

Lonser RR, Gogate N, Morrison PF, Wood JD, Oldfield EH (1998) Direct convective delivery of macromolecules to the spinal cord. J Neurosurg 89(4):616-622.

Laske DW, Morrison PF, Lieberman DM, Corthesy ME, Reynolds JC, Stewart-Henney PA, Koong SS, Cummins A, Paik CH, Oldfield EH (1997) Chronic interstitial infusion of protein to primate brain: determination of drug distribution and clearance with single-photon emission computerized tomography imaging. J Neurosurg 87(4):586-594.

Lieberman DM, Laske DW, Morrison PF, Bankiewicz KS, Oldfield EH (1995) Convection-enhanced distribution of large molecules in gray matter during interstitial drug infusion. J Neurosurg 82(6):1021-1029.

Bobo RH, Laske DW, Akbasak A, Morrison PF, Dedrick RL, Oldfield EH (1994) Convection-enhanced delivery of macromolecules in the brain. Proc Natl Acad Sci U S A 91(6):2076-2080.

Morrison PF, Laske DW, Bobo H, Oldfield EH, Dedrick RL (1994) High-flow microinfusion: tissue penetration and pharmacodynamics.Am J Physiol 266(1 Pt 2):R292-305.

See: Targeted Toxins

Q: I’m interested in using SAP to eliminate cells through retrograde transport, like OX7-SAP (Cat. #IT-02) and IB4-SAP (Cat. #IT-10) have been used. Can you explain how retrograde transport works and if it is possible for this to work with dermorphin-SAP (Cat. #IT-12)? What determines whether a targeted toxin will be able to be used in retrograde transport?

A: Current evidence indicates that effective suicide transport agents undergo endocytosis at nerve terminals followed by retrograde axonal transport of the endocytic vesicles containing the toxin. Experiments using vincristine have shown that the retrograde axonal transport of suicide transport toxins utilizes the fast transport system (microtubules). However, it is not known what determines whether or not a specific toxin-ligand undergoes axonal transport after internalization.

Empirically, it has been observed that immunotoxins (OX7-SAP, 192-Saporin or 192-IgG-SAP [Cat. #IT-01], anti-DBH-SAP [Cat. #IT-03]) and lectin-toxins (ricin, volkensin, IB4-SAP) all undergo retrograde axonal transport and are therefore effective suicide transport agents. This is not true, however, for neuropeptide-toxin conjugates, such as dermorphin-SAP. For example, in an unpublished study, we injected large doses (1-2 µg) of dermorphin-SAP into the lumbar intrathecal space of rats. After 2-3 days, rats were sacrificed and lumbar dorsal root ganglia examined for evidence of toxin effect (striking chromatolysis). None was found after examining numerous ganglia and >15,000 primary afferent neurons. Apparently, dermorphin-SAP is not retrogradely transported even if it is taken into the primary afferent terminals that express the mu opioid receptor (MOR).

Q: If a targeted toxin cannot be used in retrograde transport, will it only kill cell bodies in the injection site or will it also kill terminals?

A: Current evidence suggests that applying dermorphin-SAP (Cat. #IT-12) to the population of MOR-expressing neurons in the dorsal horn of the spinal cord results in destruction only of the neurons in lamina II and not the primary afferent terminals that also express MOR. This may be a general principle but it has not been tested in any other situation for dermorphin-SAP, nor have SP-SAP (Cat. #IT-07) and SSP-SAP (Cat. #IT-11) been evaluated for terminal uptake and suicide transport. Any saporin taken into a nerve terminal should not be toxic unless retrogradely transported to the cell body since there are no ribosomes (site of saporin action) or protein synthesis in the nerve terminal.

See: Targeted Toxins

Suggested Reading:

1. Oeltmann TN, Wiley RG (1986) Wheat germ agglutinin-ricin A-chain conjugate is neuronotoxic after vagal injection. Brain Res 377:221-228.
2. Wiley RG, Stirpe F, Thorpe P, Oeltmann TN (1989) Neuronotoxic effects of monoclonal anti-Thy 1 antibody (OX7) coupled to the ribosome inactivating protein, saporin, as studied by suicide transport experiments in the rat. Brain Res 505:44-54.
3. Contestabile A, Fasolo A, Virgili M, Migani P, Villani L, Stirpe F (1990) Anatomical and neurochemical evidence for suicide transport of a toxic lectin, volkensin, injected in the rat dorsal hippocampus. Brain Res 537(1-2):279-286.
4. Pangalos MN, Francis PT, Pearson RC, Middlemiss DN, Bowen DM (1991) Destruction of a sub-population of cortical neurones by suicide transport of volkensin, a lectin from Adenia volkensii. J Neurosci Methods 40(1):17-29.
5. Wiley RG (1992) Neural lesioning with ribosome-inactivating proteins: suicide transport and immunolesioning. Trends in Neurosci 15:285-290.
6. Roberts RC, Harrison MB, Francis SMN, Wiley RG (1993) Differential effects of suicide transport lesions of the striatonigral or striatopallidal pathways on subsets of striatal neurons. Exp Neurol 124:242-252.
7. Contestabile A, Stirpe F (1993) Ribosome-inactivating proteins from plants as agents for suicide transport and immunolesioning in the nervous system. Eur J Neurosci 5:1292-1301.
8. Wiley RG, Lappi DA(1994) Suicide Transport and Immunolesioning. R.G. Landes, Houston.
9. Roberts RC, Strain-Saloum C, Wiley RG (1995) Effects of suicide transport lesions of the striatopallidal or striatonigral pathways on striatal ultrastructure.Brain Res 710:227-237.
10. Wiley RG, Kline IVRH (2000) Neuronal lesioning with axonally transported toxins. J Neurosci Methods 103:73-82.

Q: How do I know my peptide will work as a targeted toxin?

A: There is rich literature that demonstrates peptides can usher proteins that inhibit protein synthesis (such as saporin) into cells and result in cell death. Peptide ligands that bind to the cell surface (i.e., to their receptors) are internalized-in fact, often quite rapidly. As with all saporin cytotoxins, internalization is necessary; antagonists that do not internalize would not be expected to be proper agents for a saporin cytotoxin. All agonists that have a decent affinity and internalization rate should work as a targeted toxin.

Q: How much peptide do I need to provide for a custom conjugation?

A: Actually, we will consult with you on the structure function properties of your peptide. We will need to synthesize an entirely new peptide for conjugation to saporin. We will, in collaboration with you and/or by examination of the literature, design the new peptide and have it synthesized (it is our plan to have peptide synthesis capabilities in 2003). We pass the price of the peptide, usually quite reasonable, directly to you without any increase.

Q: How much of the saporin conjugate will that give me?

A: We strive to give you 2-3 mg of peptide-saporin cytotoxin. These often are effective in the nanogram range.

Q: What is the ratio of saporin to antibody?

A: We synthesize the conjugate such that there is one mole of saporin per mole of peptide.

Q: What quality control is involved?

A: We monitor the reactions and purification by several means. The product is confirmed by gel electrophoresis. A data sheet will be provided when we ship the immunotoxin to inform you of final average molecular weight.

Q: What is the cost of a custom targeted toxin preparation? How long will it take to complete?

A: The standard cost of a peptide-saporin conjugation is US$3500.00 (as of March 2003), plus the price of the peptide. From the time we receive the peptide to the time we ship out the finished targeted toxin is 2-3 weeks.

See: Custom Conjugates

Q: How do I know my antibody will work in an immunotoxin?

A: We recommend that you use one of our second immunotoxins (secondary conjugates) to test for specificity and internalization of your antibody.

Q: How much antibody do I need to provide for a custom conjugation?

A: The required quantity is 8-15 mg of purified monoclonal antibody.

Q: How much of the saporin conjugate will that give me?

A: The yield is 15-30% in mg of immunotoxin from the number of mg of original antibody.

Q: What is the ratio of saporin to antibody?

A: The amount of saporin can vary between 1.5-3 moles saporin per mole of antibody.

Q: What quality control is involved?  Will you provide product specifications such as average saporin to antibody ratio?

A: We monitor the reactions and purification by several means.  The product is confirmed by gel electrophoresis. A data sheet will be provided when we ship the immunotoxin to inform you of final average molecular weight.

Q: What is the cost of a custom immunotoxin preparation? How long will it take to complete?

A: The standard cost of an antibody-saporin conjugation is US$4500.00 (as of Dec 2007).  From the time we receive the purified antibody to the time we ship out the finished conjugate is 2-3 weeks.

See: Custom Conjugates , ZAP Conjugates

Q: You have stated that it was unlikely that saporin compounds or constituents would be excreted in urine or feces. However, you acknowledge that experimental data is lacking. Have there been any tests of animal urine or feces for saporin content? My animal care staff are concerned.

A: One of the reasons that no studies have been done on excretion of saporin is that there isn’t much on the theoretical side to cause concern. The primary issue is that the quantity used in mice (and even rabbits) is so small that when looked at in human terms (i.e., an animal 10 to 100-times larger), the dosage becomes insignificant. The LD50 for saporin in mice is 4-8 mg/kg;1 that would translate in humans to more than you’ll ever use! The immunotoxins, which contain only about 20% saporin by weight, really do not contain all that much saporin.

Looking at it another way, you need a concentration of about 100 nM to see even a vague hint of toxicity of saporin to cells. In human blood, that would correspond to 24 mg injected systemically into a person. It would be really expensive for anyone to get close to that number.

As far as urine and feces goes, the same calculations are appropriate, but there will be considerable degradation – the protein content in urine and feces is quite low and the probability is that you will be dealing with only saporin. Remember saporin is a plant protein that is related to proteins in foods that we eat (cucumbers, for example).

Q: Are there any studies which indicate what doses of saporin (by itself or compounded with an antibody) would be hazardous if ingested or injected (i.e. systemic dose level resulting in death or organ dysfunction).

A: When there is an antibody that does recognize a human epitope (the human p75-saporin immunotoxin that is used in rabbits, for example), at about 1 pM one sees the slightest bit of toxicity to cells. That translates, if injected by error into a human blood supply, to about 170 micrograms. That also is a gigantic dose. I am using very conservative numbers here, and the bottom line is that you cannot accidentally reach such dangerous levels under normal handling situations.

Having said all this, we still recommend that our customers take excellent care of themselves and we state clearly that precautions should be taken by people handling these materials, just as they should use precautions with all laboratory chemicals. Please refer to the data sheets provided with our products for safety instructions.

See: Saporin (Cat. #PR-01)

References

1. Stirpe F et al. Hepatotoxicity of immunotoxins made with saporin, a ribosome-inactivating protein from Saponaria officinalis. Virchows Arch B Cell Pathol Incl Mol Pathol 53(5):259-271, 1987.

Safety Instructions

Good laboratory technique must be employed for the safe handling of this product. This requires observation of the following practices:

1. Wear appropriate laboratory attire, including lab coat, gloves and safety glasses.

2. Do not pipet by mouth, inhale, ingest or allow product to come into contact with open wounds. Wash thoroughly any part of the body which comes into contact with the product.

3. Avoid accidental autoinjection by exercising extreme care when handling in conjunction with any injection device.

4. This product is intended for research use by qualified personnel only. It is not intended for use in humans or as a diagnostic agent. Advanced Targeting Systems is not liable for any damages resulting from the misuse or handling of this product.

For disposal: autoclave, or expose to 0.2 M NaOH, materials that come into contact with the toxin.

Q: We’re submitting a protocol to our IACUC to use IB4-SAP (Cat. #IT-10). We plan to inject the targeted toxin and then sacrifice the animal ten days later. What, if any, are the safety issues here?

A: The only danger to lab personnel from IB4-SAP would be accidental self-injection, and even then, at the doses typically used in rats, it would only produce very localized effects at the injection site.

Once injected into animals, the agent is rapidly rendered inaccessible to anyone else by binding, internalization and eventual catabolism. It is extremely unlikely that intact toxin would ever be excreted or recoverable from the rats. The components of the toxin, IB4 and saporin, by themselves are no toxic threat. We use no special precautions with such rats except appropriate care for whatever neurologic deficits they develop, i.e. foot drop, autotomy, etc.

One caveat: To the best of my knowledge the above statements are accurate, but I do not know of any experimental data that directly addresses the issues. I base my comments on our long experience with similar agents including ricin and volkensin which are much more toxic and unstable.

See: Targeted Toxins

Q: How long does it take to see the cell death occurring from the use of targeted toxins using saporin? Is there a time course of hours or days?

A: Details of the time course of early events have not been extensively studied. After ricin injections into the cervical vagus nerve, the proximal nerve becomes unresponsive to electrical stimulation between 36 and 48 hours. After septal injection of 192-Saporin (192-IgG-SAP, Cat. #IT-01), hippocampal theta rhythm begins to diminish on the third postoperative day and reaches a minimum by 7 days which is maintained indefinitely. Anatomical disintegration is complete within 10-14 days after injection of most toxins.

Q: Will this time course be the same regardless of the targeted toxin used or the method of administration?

A: Presumably, injection of toxin into the vicinity of target cell bodies and dendrites should produce effects somewhat sooner than toxin injections into axonal terminal fields where retrograde axonal transport must first deliver toxin to the perikarya. In the cervical vagus, based on transport times for ricin and inhibition of toxin transport by vincristine, we concluded that fast axonal transport is involved. Colchicine coinjected intraventricularly with 192-Saporin (192-IgG-SAP, Cat. #IT-01) prevents destruction of cholinergic basal forebrain neurons suggesting that fast axonal transport also is involved with i.c.v. toxin injections. Consequently, the delay introduced by injecting toxin into axon terminal fields is usually a few hours at most.

Q: What are some assays/methods to use to be able to graphically demonstrate cell death?

A: Toxin-induced cell death can be observed and documented with a variety of techniques. Often the easiest is simple Nissl staining because all of the RIP toxins (ricin, volkensin, saporin) produce profound chromatolysis that is readily apparent in Nissl stains (i.e. cresyl violet).

Electron microscopy can demonstrate details of neuron degeneration including loss of axon terminals at a distance from the cell body which can be useful in anatomic tracing studies.

Typically, target neurons express proteins that can be visualized with immunocytochemical techniques. Thus, immunofluorescence or peroxidase immunohistochemistry can be useful in detecting loss of staining for target molecules and co-expressed molecules in the neurons being targeted. The use of multiple markers is recommended to insure that cell loss occurred rather than down regulation of marker expression.

See: Targeted Toxins

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

Q: Can you use targeted toxins in vivo?

A: Yes, Molecular Neurosurgery is designed as a tool for in vivo use.

Q: How do you recommend administration of the targeted toxin?

A: There are several ways to administer the toxins depending on the cells being targeted:

1. Direct intraparenchymal pressure microinjection can be used to deliver the targeted toxin directly to target cells. This approach has been used successfully with several toxins, including SP-Saporin (SP-SAP, Cat. #IT-07), in the striatum to kill striatal interneurons that express the NK-1 receptor. Long slow infusions (0.1 µl/min) are probably the best way to do intraparenchymal injections. [1]

2. Targeted toxins can also be injected into terminal fields and retrogradely transported to the cell bodies. This approach has been used successfully to selectively destroy locus coeruleus noradrenergic neurons that project to the olfactory bulb by injecting anti-DBH-saporin (Anti-DBH-SAP, Cat. #IT-03) into the olfactory bulb.[2]

Intracortical injections of 192-Saporin (192-IgG-SAP, Cat. #IT-01) also have been used to destroy cholinergic basal forebrain neurons projecting to the injected patch of cortex.[3]

Lumbar subarachnoid injections of SP-Saporin (SP-SAP, Cat. #IT-07) can destroy lamina I neurons in the dorsal horn that express the NK-1 receptor.[4]

3. Lastly, SP-Saporin (SP-SAP, Cat. #IT-07) has also been applied directly to the surface of the spinal cord to kill lamina I neurons expressing NK-1 receptor. In all cases, pilot studies to determine optimal toxin dose and injection parameters are recommended.

See: Targeted Toxins

References

1. Wiley RG et al. Destruction of neurokinin-1 receptor expressing cells in vitro and in vivo using substance P-saporin. Neurosci Lett 230:97-100, 1997.
2. Blessing WW et al. Destruction of locus coeruleus neuronal perikarya after injection of anti-dopamine-beta-hydroxylase immunotoxin into the olfactory bulb of the rat. Neurosci Lett 243:85-88, 1998.
3. Wiley RG et al. Immunolesioning: Selective destruction of neurons using immunotoxin to rat NGF receptor. Brain Res 562:149-153, 1991.
4. Mantyh PW et al. Inhibition of hyperalgesia by ablation of lamina I spinal neurons expressing the substance P receptor. Science 278:275-279, 1997.