targeted-toxins

Sheehan JJ, Tsirka SE (2002) Reduction of microglia cell populations before induction of excitotoxicity reduces neurodegeneration. Neuroscience 2002 Abstracts 606.9. Society for Neuroscience, Orlando, FL.

Summary: Excitotoxicity is thought to be a component of many neurodegenerative diseases including Alzheimer’s and stroke. In excitotoxicity, as well as other injury models, microglia have been found to have both neuroprotective and neurodegenerative roles. To lend further insight into this controversy we utilized an immunotoxin selective for monocyte derived cell populations including microglia. The immunotoxin will selectively kill microglia and is not toxic to neurons or other glia populations in culture. In addition, infusion of the immunotoxin into the hippocampus of C57/Bl mice results in a selective reduction in endogenous microglial cell populations in this region. Furthermore, this reduction occurs without any perturbation of other cell types or the extracellular matrix. If depletion of microglia in this manner precedes excitotoxic injury, then hippocampal neurodegeneration is significantly reduced. These results agree with other work in our lab, which suggests that microglial cells exhibit neurotoxic properties in excitotoxicity.

Related Products: Mac-1-SAP mouse/human (Cat. #IT-06)

Gibbs RB (2002) Basal forebrain cholinergic neurons are necessary for estrogen to enhance acquisition of a delayed matching-to-position T-maze task. Horm Behav 42(3):245-257. doi: 10.1006/hbeh.2002.1825

Summary: The author investigated the role of cholinergic neurons of the basal forebrain in cognitive function using a long-term hormone replacement model in rats. Septal infusions of either 1.0 µg or 0.22 µg 192-Saporin (Cat. #IT-01) prevented the therapeutic effects of hormone replacement on cognitive function.

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

Salo PT, Hogervorst T, Seerattan RA, Rucker D, Bray RC (2002) Selective joint denervation promotes knee osteoarthritis in the aging rat. J Orthop Res 20(6):1256-1264. doi: 10.1016/S0736-0266(02)00045-1

Summary: Noting that mice lose joint afferents with aging, and that this loss precedes osteoarthritis development, the authors investigated the effects of denervating the knee joints of young rats. Injection of 10 µl OX7-SAP (Cat. #IT-02) into the knee joint space produced severe degenerative cartilage changes as well as a significant reduction in the number of joint afferents. These changes indicate that joint denervation predisposes a joint to osteoarthritic changes more severe than those found with aging alone.

Related Products: OX7-SAP (Cat. #IT-02)

Blanco-Centurion CA, Gerashchenko D, Murillo-Rodriguez E, Shiromani PJ (2002) Simultaneous neurotoxic lesions of noradrenergic LC, histaminergic TMN and cholinergic BF neurons do not elicit hypersomnia whereas lesions of the hypocretin-containing LH neurons do. Neuroscience 2002 Abstracts 577.16. Society for Neuroscience, Orlando, FL.

Summary: Wakefulness is believed to be due to activation of neurons in the locus coeruleus (LC), tuberomammillary nucleus (TMN) and the basal forebrain (BF). These neurons receive a heavy projection from hypocretin (HCRT) neurons. It has been proposed that the HCRT neurons maintain wakefulness via their innervation of these three groups of neurons. Here we test this hypothesis by lesioning the LC, TMN and the BF. Sprague-Dawley rats implanted with sleep recording electrodes were given microinjections of the following saporin neurotoxins to lesion specific neurons: α-DBH-saporin (vol=0.4 μL; 1 μg/μL, LC lesion) , HCRT2-saporin (vol=0.4 μL; 0.20 μg/μL, TMN lesion) and 192IgG-saporin (vol=0.5 μL; 0.4 μg/μL, BF lesion). Six rats given saline injections served as controls. Immediately after surgery sleep recordings were made continuously for three weeks. In rats that had double lesions (n=7)(combinations of LC, TMN or BF) sleep was not increased. In two rats the LC, TMN and BF were destroyed (>95%) but there was no hypersomnia either. However, one rat that had a triple lesion and also had 30% loss of HCRT neurons showed significant and persistent hypersomnia. Previously, lesion of a single wake-active neuronal population has not been found to increase sleep. We have now found that double or triple lesions also do not produce hypersomnia. Only when the HCRT neurons are lesioned, sleep is affected. This suggests that HCRT neurons play a primary role in waking and the LC, TMN or BF neurons do not mediate this function.

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

Mantyh PW (2002) Neurobiology of substance P and the NK1 receptor. J Clin Psychiatry 63(Suppl 11):6-10.

Summary: The NK-1 receptor system is somewhat unusual in that it is expressed on only 5-7% of neurons in the central nervous system. Dr. Patrick Mantyh reviews how tools such as SP-SAP (Cat. #IT-07) have been used to begin defining the roles of substance P and the NK-1 receptor in affective behavior.

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

Forster HV, Hodges MR, Wenninger JM, Pan LG, Klum L, Leekley T, Feroah TR, Brozoski DT (2002) Breathing of awake goats after neurotoxic lesions in the medullary raphe. Neuroscience 2002 Abstracts 321.9. Society for Neuroscience, Orlando, FL.

Summary: Neurokinin I immunoreactive neurons are abundantly present in the medullary raphe of adult goats. We therefore wished to determine the effect on breathing of destroying such neurons using the neurotoxin saporin (SAP) conjugated to substance P (SP). Injections (1 to 10 µl) of SAP-SP were made at one or two sites in the raphe pallidus and/or raphe obscurus of 4 awake goats. Over the subsequent 5 hours, breathing remained near control levels. Within a few days, there was mild to marked hypoventilation in 2 goats and an attenuated CO2 sensitivity in 3 goats but breathing did not become irregular or ataxic in any goat. The attenuated CO2 sensitivity was associated with evidence of airway constriction. Eight to 14 days later, we injected (1 to 10 µl) at the same sites 50mM ibotenic acid (neurotoxic through glutamate receptors). In the awake state, this injection caused a further marked hypoventilation in one goat who became terminally apneic when anesthetized. After this injection, in the other 3 goats, eupneic PaCO2 was stable and CO2. sensitivity was normal or below normal. We conclude that in awake goats, normal eupneic breathing and CO2 sensitivity are dependent on medullary raphe neurokinin and glutamate receptor activity which apparently includes but is not limited to regulation of airway diameter.

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

Gallegos RA, Lee RS, Crawford E, Wills DN, Carr JR, Zhukov VI, Slaght KE, Huitron-Resendiz S, Criado JR, Henriksen SJ (2002) Selective lesion of ventral tegmental area neurons expressing mu-opioid receptors alters EEG power spectrum across sleep/wake cycle. Neuroscience 2002 Abstracts 276.14. Society for Neuroscience, Orlando, FL.

Summary: The ventral tegmental area (VTA) has long been implicated in motivated behaviors. Our previous study (Lee et al, J Neurosci 2001) also suggests a role for VTA GABAergic neurotransmission in REM sleep. In the current study the potential role of the VTA in modulating electroencephalogram (EEG) activation was explored by selectively deactivating mu-opioid receptor expressing cells in the VTA. Under sodium pentobarbital anesthesia, rats received either (1) a sham operation (2) a single bilateral VTA injection of NMDA (3) a saporin injection or (4) an injection of a dermorphin-saporin (DERM-SAP) conjugate (Advanced Targeting Systems, San Diego). Animals were also fitted with skull electrodes for recording the EEG. The filtered EEG was recorded continuously for 24 hours beginning 21 to 28 days after surgery. Frequency analysis of the EEG in 15-sec epochs revealed differences in the distribution of relative power in the DERM-SAP animals, compared to controls. Low frequency components (0.5-3.0 Hz and 3.0-8.0 Hz) were enhanced in dual lesioned animals during the dark phase but only during sleep. These results indicate that a selective inactivation of cells in the VTA has specific effects on arousal mechanisms in the intact animal.

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

Burgess SE, Gardell LR, Xie Y, Ossipov MH, Vanderah TW, Malan TP, Porreca F, Lai J (2002) Dermorphin-saporin targets descending facilitation in the rostral ventromedial medulla (rvm) to block CCK-induced abnormal pain. Neuroscience 2002 Abstracts 351.11. Society for Neuroscience, Orlando, FL.

Summary: Abnormal pain from L5/L6 spinal nerve ligation (SNL) has been shown to require a time-dependent activation of descending facilitatory pathways arising in the RVM. Additionally, RVM microinjection of L365,260, a cholecystokinin (CCKB) receptor antagonist, reverses SNL-induced tactile and thermal hyperalgesia. These observations suggest the possibility that RVM CCK might “drive” such facilitation from the RVM by activating the endogenous descending facilitation system. Rats were treated with a single RVM injection of dermorphin (DERM) (μ opioid agonist), unconjugated saporin (SAP), or dermorphin-saporin (DERM-SAP) and responses to non-noxious tactile (von Frey filaments) or noxious radiant heat stimuli applied to the hindpaw were measured before and after RVM microinjection of CCK to uninjured rats. RVM DERM-SAP, DERM or SAP did not significantly alter baseline sensory thresholds over 28 days post-injection. At day 28, the rats received bilateral microinjections of CCK (30ng) in the RVM. Rats pretreated with DERM or SAP showed a time-related and revsersible CCK-induced tactile and thermal hypersensitivity. In contrast, RVM CCK failed to produce changes in sensory threshold in animals pretreated with DERM-SAP. The RVM pretreatments did not alter responses in control rats challenged with CCK vehicle. Additionally, lesions of the dorsolateral funiculus also blocked RVM CCK-induced tactile and thermal hypersensitivity. These data support the possibility of CCK-mediated activation of descending facilitation from the RVM as a mechanism of neuropathic pain.

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

Guyenet PG, Stornetta RL, Rosin DL, Wang H, Sevigny CP, Weston MC (2002) Somatostatin immunoreactivity is a diagnostic marker of the pre-Boetzinger complex. Neuroscience 2002 Abstracts 362.4. Society for Neuroscience, Orlando, FL.

Summary: Selective ablation of the neurokinin-1 receptor-ir (NK1R-ir) neurons of the ventral respiratory group (VRG) causes major respiratory deficits. Since this population of NK1R-ir neurons is heterogeneous, additional markers are needed to identify which subgroup is most critical to respiratory rhythmogenesis. In the present study, the pre-Boetzinger complex (pre-BoetC) was defined as a 500 μ-long segment of the ventral respiratory group (VRG) located rostral to the spinally projecting inspiratory premotor neurons. This region of the ventral medulla was the only one that contained somatostatin-immunoreactive (SST-ir) neuronal somata. These cells were small (108 μ²), generally fusiform and they expressed very high levels of preprosomatostatin (PPSST) mRNA. All SST-ir neurons were strongly NK1R-ir and were destroyed by saporin conjugated with an NK1R agonist. Most SST-ir neurons (>90%) contained vesicular glutamate transporter 2 (VGLUT2) mRNA whereas <1% contained GAD-67 mRNA and few (6%) contained preproenkephalin mRNA. The results of retrograde labeling experiments with Fluoro-Gold demonstrated that SST-ir neurons do not project to the spinal cord but that over 75% project to the contralateral pre-BoetC. In conclusion, somatic SST immunoreactivity can be used as a diagnostic marker of the pre-BoetC. The SST-ir cells of the pre-BoetC are small glutamatergic interneurons with contralateral projections and they express high levels of NK1 receptors. The homogeneous features of this group of interneurons and their exclusive location in the pre-BoetC suggest that they could be the NK1R-ir neurons whose destruction disrupts respiratory rhythm. (HL 28785 & 60003).

Related Products: SSP-SAP (Cat. #IT-11)

Meng ID, Harasawa I, Lai J, Porreca F, Fields HL (2002) Changes in rostral ventromedial medulla (RVM) neurons after the selective loss of mu-opioid receptor expressing cells. Neuroscience 2002 Abstracts 351.9. Society for Neuroscience, Orlando, FL.

Summary: Different subpopulations of RVM neurons inhibit or facilitate dorsal horn nociceptive transmission. Microinjection of saporin conjugated to the mu-opioid receptor (MOR) agonist dermorphin (derm-sap) into the RVM selectively ablates MOR expressing neurons and diminishes neuropathic pain symptoms (Porreca et al., 2001). We examined the properties of neurons surviving a single RVM injection of derm-sap or sap control. Three classes of RVM neurons (On, Off, and Neutral) have been described with distinct responses to noxious stimuli and MOR agonists. On-cells increase and Off-cells cease firing just prior to a tail flick; MOR agonists inhibit On-cells and disinhibit Off-cells. Neutral cells are unaffected by either noxious stimulation or MOR agonists. Using single unit recording in lightly anesthetized rats a total of 10 electrode tracks were made per rat and each unit encountered was characterized according to its tail flick related activity. Injection of derm-sap (n=8) resulted in fewer On- and Off-cells when compared to saporin controls (n=8). The number of Neutral cells remained unchanged. In separate experiments, after derm-sap pretreatment RVM injections of the MOR agonist DAMGO were ineffective whereas injections of the glutamate receptor agonist homocysteic acid into the same sites increased tail flick latencies. The decrease in number of On-cells after derm-sap is consistent with evidence that these neurons express MOR and facilitate nociceptive transmission. The decrease in number of Off-cells indicates that inhibitory neurons responsible for producing the Off-cell tail flick related pause also express MOR.

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