sfn2000

Siddiq MM, Tsirka SE (2000) Elimination of microglia suggests their involvement in neuronal plasticity. Neuroscience 2000 Abstracts 507.2. Society for Neuroscience, New Orleans, LA.

Summary: Reorganization of mossy fibers occurs in the mammalian hippocampus during consolidation of learning and memory. Induced low level seizures with kainic acid (KA) result in the development of new synapses and the reorganization of existing ones along the mossy fiber pathway. The serine protease tissue plasminogen activator (tPA) is expressed along the mossy fiber pathway and has been implicated in neurite remodeling after stimulation of neuronal activity. Both neurons and microglia secrete tPA. Microglial cells are thought to function only in pathological situations in the CNS, as they exhibit neurotoxic properties. However, a protective role has been observed in the regenerating optic nerve, where intervening activated microglia were involved in tissue remodeling. To investigate whether there is a role for microglia in mossy fiber remodeling, microglia were eliminated in C57/BL6 mice by immunolesioning. The reorganization of mossy fibers was evaluated. Kainate-injected wild-type mice had pronounced mossy fiber reorganization in the dentate gyrus of the hippocampal formation as detected by Timm staining, while the immunolesioned mice had significantly less and shorter mossy fibers. It is therefore suggested that activated microglia may play a role in active remodeling of mossy fibers in the hippocampus after KA-induced seizures.

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

Mattsson A, Ögren SO, Olson L (2000) 192 IgG-saporin immunolesioning causes marked facilitation of dopamine-mediated locomotor activity in adult rats. Neuroscience 2000 Abstracts 563.7. Society for Neuroscience, New Orleans, LA.

Summary: Recent studies have indicated a possible link between changes in cholinergic mechanisms and schizophrenia. However there is limited information regarding the functional consequences of changes in ACh transmission on DA functions, which in turn are believed to be involved in schizophrenic symptoms. 192 IgG-saporin targets cells that express the low-affinity p75 neurotrophin receptor. Intracerebroventricular injection causes severe lesions of the cholinergic projections and may also damage Purkinje neurons. We have compared intracerebroventricular injections of 192 IgG SAP to adult rats (5 μg) with injections to neonate rats (0.4 μg day 4 or 0.4 μg day 4 + 0.8 μg day 13). As expected, treated adult rats are markedly impaired in the Morris swim maze both in terms of time to find the platform and in search behavior when the platform is removed, i.e. memory impairment. When tested as adults, neonatally treated animals were only modestly impaired. Interestingly, adult treated animals showed increased spontaneous motility and locomotion and markedly increased locomotor responses to amphetamine (1.5 mg/kg) as evidenced by increased rearing, motility and locomotion. These animals also responded to apomorphine (1 mg/kg) with an increased amount of rearing. There were no marked changes of locomotor activity in rats treated with 192 IgG SAP at 4 days or 4 and 13 days of age. Our results suggest that cholinergic denervation of the forebrain causes a marked enhancement of the behavior responses related to increased dopaminergic activity. However, it cannot be fully excluded that damage to non-cholinergic systems, e.g. Purkinje cells, might contribute to the effects. The striking overreaction to dopaminergic stimuli presumably caused by the cholinergic deficit is possibly relevant in relation to the role of cholinergic malfunctioning in schizophrenia.

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

De Rosa E, Hasselmo ME, Baxter MG (2000) Contribution of the cholinergic basal forebrain to proactive interference between stored odor memories during associative learning in rats: 192 IgG-saporin immunotoxic lesions. Neuroscience 2000 Abstracts 563.8. Society for Neuroscience, New Orleans, LA.

Summary: Previous electrophysiological studies and a computational model suggest that cholinergic neuromodulation may reduce olfactory associative interference during learning (Hasselmo & Bower, 1993; Hasselmo et al., 1992). Using a simultaneous discrimination task where rats were required to learn a baseline odor pair (A+B-) and then two novel odor pairs: A-C+ (with an overlapping component A) and D+E- (with no overlapping component), De Rosa & Hasselmo (2000) demonstrated that a 0.25 mg/kg systemic dose of scopolamine (SCOP) selectively increased proactive interference. Under the influence of SCOP, the rats were impaired on acquiring the odor pair AC and not the odor pair DE relative to their normal saline performance. To localize this effect male Sprague-Dawley rats, with bilateral selective cholinergic lesions of the horizontal limb of the diagonal band of Broca (HDB group) or of all of the cholinergic nuclei of the basal forebrain (BF group), were tested on our task. Neither lesion impaired normal acquisition of either odor pair relative to the sham-operated control rats. However, the BF group, but not the HDB and control groups, were sensitive to a lower dose of SCOP (0.125 mg/kg) than in the previous study: this dose selectively impaired the BF group on acquiring the odor pair AC and not the odor pair DE relative to their normal saline performance, suggesting that weaker cholinergic modulation after removing the majority of cholinergic neurons in the basal forebrain makes the system more sensitive to proactive interference during blockade of remaining cholinergic effects.

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

Rogers SD, Salak-Johnson JL, Schwei MJ, Pomonis JD, Mantyh PW (2000) Reduced anxiety related behavior following ablation of amygdala neurons expressing substance P receptor. Neuroscience 2000 Abstracts 571.2. Society for Neuroscience, New Orleans, LA.

Summary: The neurokinin substance P (SP) is localized in brain regions that coordinate stress response and may play a role in modulating anxiety. Effects of ablation of substance P receptor (SPR)-expressing neurons by administration of a substance P-toxin conjugate, substance P-saporin (SP-SAP), in the amygdala (a brain region known to modulate stress and anxiety responses) were examined immunohistochemically and behaviorally thirty days following SP-SAP treatments. Rats were bilaterally injected in basolateral amygdala nuclei with 5μl of sterile saline, 1 μM saporin (SAP), or 1 μM SP-SAP. SPR-immunofluoresence levels and number of SPR-IR positive neurons in amygdalar subnuclei decreased following SP-SAP treatment. SP-SAP did not induce significant gliosis or non-specific neuronal death. Interestingly, after SP-SAP treatment, the number of NPY-IR neurons were also decreased, and combined SPR and NPY immunofluorescence demonstrated a large number of NPY-IR neurons colocalize with SPR-IR neurons in the amygdala. Thirty days following SP-SAP treatment, rats were tested in elevated plus maze (EPM) and open field (OF). Anxiety level and exploratory behavior displayed by SP-SAP treated rats were altered; they had significantly more entries into and spent more time in EPM open arms than did saline- or SAP-injected rats. In the OF, SP-SAP treated rats spent less time frozen than saline or SAP treated rats. These results suggest that SPR expressing neurons in the amygdala plays a pivotal role in generation of anxiety behaviors and that SP may play a modulatory role in stress-induced anxiety behavior.

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

Petruska JC, Johnson RD (2000) Differential input to a nociceptive specific reflex by trka-positive and trka-negative small diameter DRG afferents. Neuroscience 2000 Abstracts 354.7. Society for Neuroscience, New Orleans, LA.

Summary: The cutaneus trunci muscle (CTM) reflex is a nociceptive specific reflex in the rat. We examined whether particular subtypes of afferents may be differentially involved in the reflex. In particular, we wanted to determine if there were differences in input to the reflex between those expressing trkA receptors, and those lacking trkA receptors. We approached this question with two techniques. The selective neurotoxin 192-saporin was injected into the left T13 DRG to destroy the p75 receptor-bearing neurons. Two to three weeks following injection, the ability of the injected DRG to elicit the CTM reflex was examined in contrast to uninjected DRG. The ganglia were also retrieved for histochemical examination. In all cases where histochemical examination revealed a clear depletion of the neurotrophin-bearing neurons the injected DRG lacked the ability to induce the CTM reflex. Histochemical markers for the trkA-negative small diameter afferents appeared normal in all cases. The second approach utilized the trans-synaptic neuronal tracer pseudorabies virus (PRV). PRV was injected into the CTM to generate a retrograde tracing of the reflex circuit, including the afferents involved. This resulted in specific labelling of many small diameter DRG neurons, the vast majority of which expressed trkA. The CTM reflex may therefore not be a suitable monitor for inputs from the trkA-negative small diameter afferents, especially as regards its use in collateral sprouting experiments. These data indicate that inputs from the two populations of afferents are likely processed differently.

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

Vogt LJ, Sim-Selley LJ, Childers SR, Wiley RG, Vogt BA (2000) Distribution of mu-opioid receptors and activated G-proteins in rat cingulate cortex and alterations following removal of noradrenergic afferents. Neuroscience 2000 Abstracts 238.1. Society for Neuroscience, New Orleans, LA.

Summary: Anterior cingulate cortex (ACC) is involved in acute and chronic pain processing. Here we define opioid architecture throughout rat cingulate cortex, relate mu-opioid receptor and G-protein stimulated binding in particular layers, and localize binding to noradrenergic terminals with immunotoxin lesions (anti-DBH-saporin). [3H]DAMGO binding was highest in areas 32 and 24 with a peak in layer I. Midcingulate area 24′ and posterior area 29 had lower and homogeneous binding. DAMGO stimulated [35S]GTPγS binding in area 24′ was similar to that in areas 32 and 24, while area 29 had very low and homogeneous binding. Undercut lesions reduced [3H]DAMGO binding in all layers with greatest loss in layer I, while DAMGO-stimulated [35S]GTPγS binding losses occurred only in layers I-III. Since neurons in the midline thalamic nuclei and locus coeruleus synthesize mu-opioid receptors, noradrenergic afferents were removed with anti-DBH-saporin. This toxin reduced [3H]DAMGO binding only in layer I of areas 32 and 24, while DAMGO-stimulated [35S]GTPγS binding increased in layer II of areas 32 and 24, had no changes in area 24′, and decreased binding in layer I of area 29. Thus, in addition to their actions on ACC neurons, other sites of opiate drug actions are through mu-opioid heteroreceptors on glutamatergic thalamic and noradrenergic locus coeruleus afferents to ACC.

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

Burgess SE, Vanderah TW, Mantyh PW, Malan Jr TP, Ossipov MH, Lappi D, Lai J, Porreca F (2000) Dermorphin-saporin targets tonic descending facilitation in the rostral ventromedial medulla to block and reverse neuropathic pain. Neuroscience 2000 Abstracts 243.6. Society for Neuroscience, New Orleans, LA.

Summary: The hypothesis that chronic pain from L5/L6 spinal nerve ligation (SNL) is due to tonic activation of descending pain facilitation mechanisms was explored by selective targeting mu (μ) opioid receptor expressing cells in the RVM (i.e., presumably, ON cells). Rats were treated with a single RVM injection of dermorphin (DERM)(μ agonist), saporin (SAP), or dermorphin-saporin conjugate (DERM-SAP) and responses to non-noxious (von Frey filaments) or noxious (Hargreave’s test) stimuli characterized. DERM-SAP retained high affinity for μ receptors and acutely produced antinociception (tail-flick test), indicating agonist actions of the conjugate. Decreased staining of μ receptor-expressing cells was seen in superficial dorsal horn and in dorsal root ganglia 28 days after intrathecal injection of DERM-SAP, but not DERM or SAP. RVM DERM-SAP, DERM or SAP did not significantly alter baseline thresholds to von Frey filaments or noxious heat applied to the paw over 28 days. At day 28, RVM pretreated rats were subjected to sham- or SNL surgery and responses to tactile and heat stimuli monitored 7 days later (i.e., 35 days after the RVM pretreatment). DERM and SAP pretreated SNL rats showed the expected development of tactile allodynia and thermal hyperalgesia, while DERM-SAP pretreated rats did not. The RVM pretreatments did not alter responses in sham-operated controls. Administration of RVM DERM-SAP, but not SAP or DERM, to SNL rats showed full reversal of established allodynia/hyperalgesia by day 14. RVM pretreatment with β-funaltrexamine (β-FNA; opioid μ antagonist) prevented the antiallodynic and antihyperalgesic effects of subsequent DERM-SAP injection. These data, together with findings of blockade of SNL pain with RVM lidocaine or lesions of the dorsolateral funiculus, support the possibility of tonic activation of descending facilitation as a basis for chronic neuropathic pain.

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

Han JS, Bizon JL, Chun HJ, Maus CE, Gallagher M (2000) Feedback HPA axis to stress is impaired in rats with selective removal of hippocampal cholinergic input. Neuroscience 2000 Abstracts 388.16. Society for Neuroscience, New Orleans, LA.

Summary: Activation of intracellular glucocorticoid receptors (GRs) may play a permissive role in mechanisms that lead to degeneration of hippocampal neurons in pathological conditions such as Alzheimer’s disease (AD). A previous study demonstrated that loss of cholinergic input from cells in the basal forebrain, a prominent feature of AD, reduced glucocorticoid receptor mRNA expression in the hippocampus in rats (Bizon et al., 1999). This experiment was conducted to see if reduced GRs after loss of cholinergic input would impair the function of the HPA axis in response to acute restraint stress. The cholinergic lesion was made by microinjections of the immunotoxin 192-IgG-saporin into the medial septal area and the vertical limb of the diagonal band. About 2 weeks later, rats were prepared with intravenous silastic catheters in the right jugular vein. After 5 days recovery, restraint stress for 1 hr was performed at 9:00 (a.m.). Blood (∼|50ul) was sampled repeatedly via the jugular catheter immediately (0 min) and at various times following the termination of the stressor (1 hr, 2 hr, 4 hr). For each group, negative feedback after a peak response to restraint was evident as a general trend of decreasing corticosterone that approached basal values by four hours after the cessation of stress. However, the speed of recovery to baseline differed between groups. Rats with loss of cholinergic input had higher corticosterone concentrations for a longer period after restraint stress than control rats, reflecting a diminished negative feedback function. These results suggest a mechanism whereby loss of basal forebrain cholinergic neurons in AD could contribute to a dysregulation of the HPA axis and more protracted exposure to high amounts of glucocorticoids. As an extension of the glucocorticoid cascade hypothesis, glucocorticoids might then be a factor in endangering hippocampal neurons in this disease.

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

Jasmin L, Arsenault P, Ohara PT, Marchand S (2000) Chronic noradrenergic spinal denervation in rats does not produce long-term hyperalgesia. Neuroscience 2000 Abstracts 243.7. Society for Neuroscience, New Orleans, LA.

Summary: Pharmacological studies have established that noradrenaline tonically inhibits spinal nociceptive transmission. We tested the hypothesis that chronically decreasing spinal noradrenaline would result in a disinhibition of nociceptive afferents resulting in behavioral hyperalgesia. We destroyed noradrenergic cells innervating the spinal cord using dopamine beta-hydroxylase antibodies linked to the neurotoxin saporin (anti-DBH-Sap). Male rats (n=6) were injected intrathecally with 4µg/10µl of anti-DBH-Sap, and their responses to nociceptive and non-nociceptive stimuli was monitored over a period of 65 days. Compared to controls (n=6), a significant (p< 0.05) decrease to hot plate (46oC) nociceptive responses could be observed during the first week post-treatment, but no differences were found at later times. At no point was there any altered response to innocuous stimuli. When tested for response to cold water stress, both treated and control animals showed analgesia, demonstrating that descending pain inhibition could still be activated. At 65 days, a formalin test showed no difference between treated (1.1 +/-0.5) and control (0.8 +/-0.5) groups. Post-mortem immunostaining of spinal cords for DBH, however, confirmed that noradrenergic denervation of the spinal cord had occurred in treated animals. These results suggest that a reorganization of the spinal cord following noradrenergic denervation is sufficient to reestablish normal nociceptive responses.

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

Miller SA, Lappi DA, Wiley RG (2000) Intrathecal dermorphin-saporin decreases morphine effect in hotplate algesia testing. Neuroscience 2000 Abstracts 212.8. Society for Neuroscience, New Orleans, LA.

Summary: The targeted cytotoxin, dermorphin-saporin, selectively destroys cells expressing MOR. In the present study, we gave dermorphin-saporin by lumbar i.t. injection and sought to determine if destroying dorsal horn neurons expressing MOR would alter thermal sensitivity and/or response to systemic morphine (MS) using hotplate testing under various conditions. 16 male Sprague-Dawley rats were tested on constant temperature (0.3, 44 and 47 C) and incremental (0.1 C/sec from 28 to 57 C) hotplates. Then 8 rats received lumbar intrathecal injections of derm-sap (465 ng) and 8 received vehicle using a subarachnoid PE-10 catheter that was removed 10 mins after injection. Retesting rats after toxin/vehicle injection showed no change in responses to any of the hotplate conditions. However, vehicle but not derm-sap rats showed increased lick latency on the incremental hotplate 20 mins after MS, 2.5 mg/kg, s.c. At 5 mg/kg of MS, vehicle and dermorphin-saporin rats showed identical responses. Capsaicin cream (0.94%) applied to the plantar surface of both hindpaws 3 hrs before testing on the 44 C hotplate produced decreased lick latencies in both groups of rats. MS, 5 mg/kg, s.c., produced increased lick latencies in capsaicin treated vehicle but not derm-sap rats. At 10 mg/kg, MS produced identical effects in capsaicin treated vehicle and toxin rats. These results indicate that i.t. derm-sap produced no change in baseline thermal sensitivity but did diminish the effect of low dose MS under conditions that preferentially test C nociceptor function suggesting that MOR-expressing dorsal horn neurons play a role in the analgesic action of low dose MS.

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