Targeting Topics 01q3

Selective destruction of medial septal cholinergic neurons attenuates pyramidal cell suppression, but not excitation in dorsal hippocampus field CA1 induced by subcutaneous injection of formalin.

Zheng F, Khanna S.

Neuroscience 103(4):985-998, 2001. PMID: 11301206

Previously, the authors have shown that an injection of formalin in the hindpaw of rats will excite a select population of CA1 pyramidal cells within a larger suppressed population. This response is accompanied by increased theta activation. The authors selectively eliminated medial septal cholinergic neurons using 192-Saporin (0.4 μl; Cat. # IT-01) to investigate the role of these neurons in response to a persistent noxious stimulus such as a formalin injection. The data indicate a CA1 network modulated by cholinergic neurons in the medial septal region may influence pyramidal cell theta and pyramidal cell suppression.

Sequential upregulation of cell adhesion molecules in degenerating rat basal forebrain cholinergic neurons and in phagocytotic microglial cells.

Hartlage-Rubsamen M, Schliebs R.

Brain Res 897(1-2):20-26, 2001. PMID: 11282354

Neurodegeneration, found in brain disorders such as Alzheimer’s, Parkinson’s, and Huntington’s diseases, is marked by a significant microglial response. This microglial activation is characterized by increased migratory activity and potential cytotoxic action on injured neurons. The interaction of microglial cells with degenerating axons and neural somata is known to be mediated by expression of cell adhesion molecules. The authors use a single intracerebroventricular injection of 192- Saporin (4 μg; Cat. # IT-01) to initiate neurodegeneration of choline acetyltransferase-immunoreactive neurons and follow the expression of two cell adhesion molecules, ICAM-1 and LFA-1, using immunohisto- chemistry. The results indicate that these adhesion molecules may function as intercellular recognition signals through which degenerating cholinergic neurons actively participate in their own targeting and removal by microglia.

Immunotoxic destruction of distinct catecholamine subgroups produces selective impairment of glucoregulatory responses and neuronal activation.

Ritter S, Bugarith K, Dinh TT.

J Comp Neurol 432(2):197-216, 2001. PMID: 11241386

Control of regulatory responses to low glucose levels in the brain have been linked to catecholaminergic neurons. Studies of these neurons have been hindered by the lack of a selective and precise lesioning agent. Ritter et al. use anti-DBH-SAP (Cat. # IT-03) to create very precise lesions of catecholamine neurons in the paraventricular nucleus of the hypothalamus and spinal cord. Injection of anti-DBH-SAP into the spinal cord eliminates cells with caudal projections while injection into the paraventricular nucleus of the hypothalamus eliminated cells with rostral projections. This ability to selectively eliminate very specific subpopulations of cells is a valuable characteristic in dissecting neuronal function.

P75-expressing elements are necessary for anti-allodynic effects of spinal clonidine and neostigmine.

Paqueron X, Li X, Eisenach JC.

Neuroscience 102(3):681-686, 2001. PMID: 11226704

It has been suggested that α2-adrenergic agonists produce analgesia by activating spinal cholinergic neurons. The authors reason that since spinal cholinergic neurons in the ventral horn express p75 following peripheral nerve trauma, cholinergic dorsal horn neurons might also. Instead, they find that dorsal horn neurons express little or no p75 under normal conditions or following spinal nerve ligation. Since dorsal horn neurons do not express p75 they are not eliminated by 192-Saporin (0.1-0.6 μg; Cat. # IT-01), but the data indicate that p75-expressing elements do play a role in pain transmission in the dorsal horn. The authors note that when afferents that express p75 are eliminated, mechanical hypersensitivity is unaffected, but the reduction of hypersensitivity by α2- adrenergic agonists or cholinergic agents is blocked.

Neuropeptide-toxin conjugates in pain research and treatment.

Wiley RG.

Reg Anesth Pain Med 25(5):546-548, 2000. PMID: 11009244

Several lines of evidence indicate dorsal horn neurons that respond to substance P (SP) play a role in nociception. Wiley discusses the attributes of SP-SAP (Cat. # IT-07), a targeted toxin that eliminates cells expressing the neurokinin-1 receptor. Animals treated with this material using a lumbar intrathecal injection show a decrease in both hyperalgesia and allodynia in several pain models. The success of SP-SAP indicates that other neuropeptides, hormones, and growth factors would be useful as targeted toxins.

Rat basal forebrain cholinergic lesion affects neuronal nitric oxide synthase activity in hippocampal and neocortical target regions.

Hartlage-Rubsamen M, Schliebs R.

Brain Res 889(1-2):155-164, 2001. PMID: 11166699

Nitric oxide (NO) mediates a variety of mechanisms in the brain including cortical perfusion, learning and memory, and neuronal plasticity. Cholinergic dysfunction has been associated with some of these same processes, notably reduced cortical cerebral blood flow and impaired performance in learning and memory tasks. The authors use a single intracerebroventricular injection of 192- Saporin (2.8 μg; Cat. # IT-01) to deplete the cholinergic neurons of the basal forebrain. Although total cortical neuronal NO synthase levels are not affected, the activity levels in select neocortical hippocampal neurons are reduced. The data suggest the ratio of catalytically active and inactive cortical NO synthase may be driven in part by basal cholinergic forebrain input.

Behavioural, histological and immunocytochemical consequences following 192 IgG-saporin immunolesions of the basal forebrain cholinergic system.

Perry T, Hodges H, Gray JA.

Brain Res Bull 54(1):29-48, 2001. PMID: 11226712

192-Saporin (Cat. #IT-01) has been used extensively as a model for Alzheimer’s Disease. The neuronal deficits caused by intraparenchymal forebrain injections (0.3-0.51 μg/μl) are apparent during tasks demanding attentional processing, but not standard tasks of learning and memory. Perry et al. compare the testing strategies for each deficit. They find that the water maze may not demand enough attentional processing to demonstrate deficits caused by this lesion. The authors also study long-term effects of 192-Saporin in rats. Although the authors produced very useful data at five to six months, they found evidence of an inflammatory response and non-specific cell death eleven months post treatment, indicating 192-Saporin may be problematic for very long-term experiments.

Septal cholinergic neurons suppress seizure development in hippocampal kindling in rats: comparison with noradrenergic neurons.

Ferencz I, Leanza G, Nanobashvili A, Kokaia Z, Kokaia M, Lindvall O.

Neuroscience 102(4):819-832, 2001. PMID: 11182245

Kindling can be caused in rats by lesioning forebrain cholinergic or noradrenergic projections. Ferencz et al. utilize 192-Saporin (2.5 μg; Cat. # IT- 01) to lesion forebrain cholinergic neurons and 6-hydroxydopamine to lesion noradrenergic neurons, administering both compounds by intraventricular injection. Upon comparing various aspects of hippocampal kindling, the authors determine that while both noradrenergic and cholinergic projections to the forebrain exert inhibitory effects, the cholinergic effect is less pronounced and occurs prior to seizure generalization.

Toxin-induced death of neurotrophin-sensitive neurons.

Wiley RG.

Methods Mol Biol 169:217-222, 2001. PMID: 11142013

Wiley discusses some of the specifics of using 192-Saporin (Cat. #IT-01) to eliminate cells expressing the rat p75 low-affinity nerve growth factor receptor. Wiley also describes the sequence of events following treatment with 192-Saporin from binding of the immunotoxin through ribosomal inactivation and cell death. Methods of handling the immunotoxin and injection are also addressed.

Model for aging in the basal forebrain cholinergic system.

Gu Z, Wortwein G, Yu J, Perez-Polo JR.

Antioxid Redox Signal 2(3):437-447, 2000. PMID: 11229357

A wide range of evidence indicates that cholinergic neurons play a role in memory and learning. Loss of these neurons is seen both in aged subjects and Alzheimer’s Disease patients. The authors discuss the use of 192-Saporin (Cat. #IT-01) to model this phenomenon. Many lesioning methods have been developed, including fimbria-fornix transections, mechanical lesions with radiofrequency or electrolysis, and intracerebral injections of excitotoxins. Information obtained through these methods suffers because non-cholinergic neurons are depleted as well as the desired cholinergic neurons. 192-Saporin provides a solution by specifically targeting and eliminating cholinergic neurons expressing p75 in the basal forebrain, closely mimicking a key component of aging.