sfn2001

Gu JG, Nakatsuka T, Tanaka E, Takeda D, Jennifer LX (2001) Capsaicin-sensitive inhibitory pathway in rat spinal cord dorsal horn. Neuroscience 2001 Abstracts 158.13. Society for Neuroscience, San Diego, CA.

Summary: The inhibitory system in the spinal cord plays an important role in regulating nociceptive sensory inputs. Here we examined inhibitory synaptic activity in lamina V neurons of the spinal dorsal horn following the activation of capsaicin VR1 receptors. Experiments were performed with spinal cord slice preparations and inhibitory postsynaptic currents (IPSCs) were recorded using patch-clamp technique. Bath application of capsaicin (2 μM) increased the amplitude and frequency of GABAergic and glycinergic spontaneous IPSCs in the majority of lamina V neurons tested. The effects of capsaicin were completely antagonized by capsazepine (10 μM), and were also blocked in the presence of tetrodotoxin (0.5 μM). However, when CNQX (20 μM) and APV (100 μM) were used to block glutamatergic synaptic transmission, the effects of capsaicin were not abolished. Furthermore, after the injection of IB4-saporin into sciatic nerve to remove IB4-positive C-primary afferent terminals, capsaicin still increased sIPSC frequency in the presence of CNQX and APV. These results suggest that inhibitory pathway could be recruited in the absence of glutamatergic inputs from primary afferents. The release of neuropeptides from capsaicin-sensitive C-primary afferents may activate GABAergic and glycinergic interneurons in superficial laminae, and the inhibitory activity may be further forwarded to lamina V neurons. The capsaicin-sensitive inhibitory pathway may play an important role in the control of nociceptive transmission in the spinal cord.

Related Products: IB4-SAP (Cat. #IT-10)

Power AE, Thal LJ, McGaugh JL (2001) Memory enhancement induced by post-training norepinephrine in the basolateral amygdala is blocked by 192-IgG saporin lesions of the nucleus basalis magnocellularis. Neuroscience 2001 Abstracts 84.13. Society for Neuroscience, San Diego, CA.

Summary: Drugs and stress hormones act in the basolateral amygdala (BLA) to modulate memory storage. The BLA projects to the nucleus basalis magnocellaris (NBM), which sends broad cholinergic projections to the neocortex. These NBM-cortex projections have been implicated in learning, memory storage and cortical plasticity. The current study was designed to test whether the cholingeric NBM-cortex projections are involved in BLA-mediated memory modulation. Rats were given bilateral cholinergic lesions of the NBM with 192-IgG saporin (0.1 μg/ 0.5 μl per side) or sham infusions, and implanted with bilateral cannulae aimed at the BLA. One week after surgery the rats were trained in the inhibitory avoidance task. Immediately after training, the rats were given bilateral infusions of norepinephrine (0.3μg, 1.0 μg, or 3.0 μg) or vehicle (0.2 μl PBS) into the BLA. On a 48-h retention test, the norepinephrine infusions produced a dose-dependent enhancement of retention (0.3μg and 1.0 μg doses) in sham-operated controls. NBM-lesioned rats that received these memory-enhancing doses of norepinephrine had retention latencies that did not differ from vehicle infused controls. Thus memory enhancement induced by post-training intra-BLA infusion of norepinephrine was blocked in 192-IgG saporin NBM-lesioned rats. ChAT assays of frontal and occipital cortices confirmed the lesions. These findings indicate that the cholinergic NBM-cortex projections are involved in BLA-mediated modulation of memory.

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Nakatsuka T, Takeda D, Gu JG (2001) α,β-methylene ATP sensitive P2X receptor mediated enhancement of glutamate release from the central terminals of Aδ primary afferents onto lamina V neurons in rat spinal cord. Neuroscience 2001 Abstracts 158.16. Society for Neuroscience, San Diego, CA.

Summary: We examined the role of αβmATP-sensitive P2X receptors in modulating glutamate release from sensory synapses of the spinal cord by using whole-cell patch-clamp recordings from dorsal horn neurons in lamina V region. The majority of lamina V neurons synapsed with terminals expressing αβmATP-sensitive P2X receptors. Application of P2X receptor agonist 100 μM αβmATP resulted in a large increase in mEPSC frequency. The increases in mEPSC frequency by αβmATP were completely abolished by the P2X receptor antagonist 10 μM PPADS, but were not blocked by Ca2+ channel blocker 30 μM La3+. αβmATP remained to be effective in increasing mEPSC frequency after the removal of superficial dorsal horn (lamina I-III) or after the injection of IB4-saporin into sciatic nerve to remove P2X3 expressing afferent terminals. Furthermore, we found that αβmATP-sensitive synapses of lamina V neurons were associated with central terminals derived from Aδ primary afferents. The EPSCs evoked by dorsal root stimulation at Aδ-fiber intensity were potentiated by 1 μM αβmATP as well as by the ecto-ATPase inhibitor 10 μM ARL67156, and depressed in the presence of 10 μM PPADS and 5 μM suramin. These results suggest that αβmATP-sensitive P2X receptors play a significant role in modulating excitatory synaptic transmission in the spinal cord.

Related Products: IB4-SAP (Cat. #IT-10)

Bailey AM, Rudisill ML, Hoof EM, Loving ML (2001) The effects of 192 IgG-saporin lesions to the nucleus basalis magnocellularis/substantia innominata (nBM/SI) on two learning set formation tasks and open field activity. Neuroscience 2001 Abstracts 85.13. Society for Neuroscience, San Diego, CA.

Summary: Male Long Evans rats (Rattus norvegicus) were used to investigate the role of the nucleus basalis magnocellularis/substantia innominata (nBM/SI) in learning set formation. Rats with bilateral 192 IgG-Saporin lesions to the nBM/SI were tested on olfactory discrimination learning set, discrimination reversal learning set, and open field activity. Assessment of open field activity indicated no group differences in general activity levels. Control animals performed significantly better than chance on trial 2 across the 50 problems given in the olfactory discrimination learning set paradigm, suggesting evidence of learning set formation. The nBM/SI lesion group did not perform significantly above chance on trial 2 overall; however, they did perform above chance on trial 2 over the last 10 problems in the olfactory discrimination learning set task. Discrimination reversal followed testing on the olfactory discrimination learning set task. No group differences were seen in discrimination reversal performance. Both control and nBM/SI lesioned animals performed well on the discrimination reversal learning set task, improving with each reversal, and both groups performed significantly higher than expected by chance on trial 2 in the discrimination reversal paradigm, indicating learning set formation. Results suggest that removal of the nBM/SI cholinergic system through 192 IgG-Saporin lesions impairs early acquisition of learning set compared to control animals, but does not interrupt later use of learning set formation.

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Stahl CE, Kusayama T, Keep M, Elmer E, Watanabe S, Borlongan CV (2001) Cyclosporine-A improves performance in passive avoidance task in adult rats with basal forebrain lesions. Neuroscience 2001 Abstracts 101.11. Society for Neuroscience, San Diego, CA.

Summary: While mainly used as an immunosuppressant, newly identified properties of CsA suggest its potential as a therapeutic agent for neurological disorders. In the present study, we investigated the effects of CsA in acquisition and retention of passive avoidance task in adult rats lesioned with 192-IgG-saporin, an immunotoxin that targets cholinergic neurons in the basal forebrain. Starting on the day of the lesion up to 7 days thereafter, animals received either daily CsA (10 mg/kg, i.p. ) or vehicle alone. On day 8 (acquisition), animals were trained in a three-compartment shuttle box passive avoidance task. Twenty-fours later, the retention tests were performed. During the acquisition phase, animals that received CsA treatment significantly entered less in the shock-associated box than those that received vehicle alone. However, the mean total acquisition times between the two groups were not statistically significant. In the retention phase, CsA-treated animals displayed significantly longer latency to stay in the safe compartment compared to vehicle-treated animals. Histological analysis using ChAT immunostaining revealed sparing (80% of control) of basal forebrain cholinergic neurons in CsA-treated animals. The use of CsA may prove beneficial for treatment of neurological disorders characterized by a dysfunctional cholinergic system.

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

Works SJ, Wellman CL (2001) Differential dendritic atrophy in frontal cortex after cholinergic lesion in young adult and aged rats. Neuroscience 2001 Abstracts 101.17. Society for Neuroscience, San Diego, CA.

Summary: Previously, we demonstrated that plasticity of frontal cortex is altered in aging rats: three months after surgery, ibotenic acid lesions of the nucleus basalis magnocellularis (NBM) produce larger declines in dendritic morphology in frontal cortex of aged rats relative to young adults. To determine whether the differential effect of the lesion was due specifically to loss of cholinergic input from the NBM, we assessed dendritic morphology in frontal cortex after cholinergic depletion in young adult and aged male rats. Rats received unilateral lesions of the NBM using 192 IgG-saporin, and sham lesions of the contralateral NBM. Two weeks after surgery, brains were stained using a Golgi-Cox procedure. Pyramidal neurons in lamina II-III of frontal cortex were drawn and dendritic morphology was quantified in three dimensions. In young adults, lesions did not alter overall branch number or length. However, in aged rats, lesions decreased basilar dendritic number and length, by 17% and 25% respectively. Furthermore, young adults demonstrated a lesion-induced redistribution of basilar dendrites: dendritic material proximal to the soma was decreased 15%, while distal dendritic material was increased as much as threefold relative to the sham-lesioned hemisphere. Alternatively, lesions in aged rats decreased the amount of distal dendritic material by 25%. Thus, the dendritic atrophy resulting from NBM lesions in aged rats occurs within two weeks after lesion, and results specifically from loss of cholinergic innervation.

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

Helm KA, Han JS, Gallagher M (2001) Selective cholinergic deafferentation affects GR mRNA expression in the rat brain. Neuroscience 2001 Abstracts 175.10. Society for Neuroscience, San Diego, CA.

Summary: Two common features of the aging process include progressive dysfunction of both the basal forebrain cholinergic (BFC) system and suprahypothalamic feedback on the hypothalamic-pituitary-adrenal (HPA) axis. Prior research has shown that an age-related reduction in glucocorticoid receptor (GR) mRNA expression occurs in cortical target sites of the BFC system, including the hippocampus, prefrontal cortex, and anterior olfactory cortex, which are highly correlated with both spatial learning impairments and a blunted negative feedback of the stress response among aged rats. Selective deafferentation of the BFC system in young rats produces a similar reduction in both GR mRNA expression in the hippocampus and the efficiency of the stress response, as measured by a protracted increase in the levels of plasma corticosterone following acute stress. The current study investigated the possibility that loss of cholinergic input from cells in the basal forebrain alters GR mRNA expression in other BFC target structures, including the medial prefrontal cortex and the anterior olfactory cortex. Lesions of the BFC system were made by microinjections of the immunotoxin IgG-192-saporin into the medial septum/vertical limb of the diagonal band, and the substantia innominata/nucleus basalis. Basal levels of plasma corticosterone measured in the morning and evening 3 weeks later did not reveal any differences between lesioned and non-lesioned rats. The abundance of GR mRNA in sections processed for quantitative in situ hybridization will include a full analysis of cortical as well as subcortical sites to reveal the extent of effects of cholinergic lesions on GR mRNA expression throughout the brain. Supported by NIA PO1-AG09973.

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Janni G, Jasmin L, Ohara PT (2001) Schwann cells can enter the demyelinated spinal cord from dorsal roots via scar tissue. Neuroscience 2001 Abstracts 157.4. Society for Neuroscience, San Diego, CA.

Summary: We have studied the routes of entry of Schwann cells into the demyelinated spinal cord. Following application of the toxin CTB-Sap (B fragment of Cholera toxin conjugated to Saporin) into the intrathecal space of adult rats there occurs massive loss of oligodendrocytes with secondary demyelination of the lumbar spinal cord with sparing of axons. Concurrent with the demyelination, an arachnoiditis develops that results in dorsal roots becoming adherent to the lateral spinal cord. Light and electron microscopy showed that Schwann cells in the dorsal roots were always separated from the demyelinated axons by a mesenchymal interface part of which was formed by the dorsal root perineurium. Within 15 days of the demyelination, Schwann cell precursors (p75 immunopositive) migrated from the dorsal roots into the spinal cord via the adhesions and were found to divide within the cord. Schwann cell myelination of demyelinated central axons was consistently observed by day 30. Therefore the Schwann precursors were able to migrate into demyelinated spinal cord through non-neuronal cellular barriers without being in direct contact with demyelinated axons. These findings suggest that, under appropriate conditions, Schwann cells might be introduced therapeutically into the demyelinated spinal cord via intrathecal application and avoid direct spinal injection.

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Burk JA, Herzog CD, Porter MC, Mahoney J, Bruno JP, Sarter M (2001) Interactions between partial cortical cholinergic deafferentation and aging on sustained attention performance in rats. Neuroscience 2001 Abstracts 202.5. Society for Neuroscience, San Diego, CA.

Summary: Previous studies have provided only limited support for the idea that aging alone impairs the functions of basal forebrain corticopetal cholinergic neurons. Conversely, aging has been hypothesized to exacerbate the functional consequences of prior insult to, or degenerative processes in, the basal forebrain cholinergic system. The present study assessed the effects of aging on the sustained attention performance of rats with moderate lesion-induced loss of cortical cholinergic inputs. Previous studies on the effects of extensive (> 70 %) cortical cholinergic deafferentation indicated that the integrity of this system is necessary for the animals’ ability to detect rare and unpredictable visual signals. In the present longitudinal experiment, moderate (< 50 %) 192 IgG-saporin-induced loss of cortical cholinergic inputs, produced in well-trained, 16 month-old rats, did not – as was intended - immediately affect their attentional performance. Animals continued to undergo attentional performance training for the remainder of their lives. At the age of 31 months, impairments in performance began to emerge in lesioned animals. Compared to their sham-lesioned counterparts, lesioned animals exhibited a steeper decrement in their ability to detect hits in the course of a test session. At this age, the performance of sham-lesioned animals did not differ from their earlier performance prior to and immediately after the lesion. These results support the general hypothesis that aging serves to exacerbate the effects of pre-existing degeneration of the basal forebrain cholinergic system.

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

Rinaman L, Wonders CP (2001) Targeted destruction of A2/C2 catecholamine neurons alters hypothalamic responses to vagal stimulation. Neuroscience 2001 Abstracts 131.4. Society for Neuroscience, San Diego, CA.

Summary: Central catecholamine (CA) pathways participate in viscerosensory modulation of hypothalamic neuroendocrine function. Different brainstem CA cell groups may relay different types of viscerosensory signals to different classes of hypothalamic effectors. The present study sought to determine the role of dorsal medullary A2/C2 neurons in hypothalamic responses to exogenous cholecystokinin (CCK), which activates gastrointestinal vagal sensory inputs to the caudal brainstem. Saporin toxin conjugated to dopamine-beta-hydroxylase antibody (anti-DbH-sap; 10 ng in 100 nl) or control toxin was microinjected unilaterally or bilaterally into the A2/C2 region of the dorsal vagal complex in adult male rats. After 10-14 days, rats were injected i.p. with CCK (10 ug/kg) and perfused with fixative 1 hr later. Brainstem and forebrain sections were processed for dual immunocytochemical detection of cFos (a marker of neural activation) and DbH (to define the lesion). Additional forebrain sections were processed for cFos and either oxytocin (OT), vasopressin (AVP), or corticotropin-releasing factor (CRF) to identify hypothalamic neurons activated by CCK. Anti-DbH-sap destroyed the majority of A2/C2 neurons within the microinjection site(s), with minimal non-specific damage. A2/C2 lesions markedly attenuated CCK-induced activation of OT neurons and, to a lesser extent, attentuated CRF activation. Conversely, CCK-induced cFos expression was significantly increased in AVP neurons. The latter effect was observed only after bilateral lesions. These results indicate that A2/C2 neurons participate in vagal sensory-mediated stimulation of OT neurons and CRF neurons, and inhibition of AVP neurons.

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