sfn2002

McGaughy JA, Rubin S, Stollstorff M, Baxter MG, Eichenbaum HB (2002) 192 IgG-saporin-induced cortical, cholinergic deafferentation in rats produces a dissociation in the function of prelimbic/infralimbic and orbitofrontal cortex in an attentional set-shifting task. Neuroscience 2002 Abstracts 674.4. Society for Neuroscience, Orlando, FL.

Summary: Converging data support the hypothesis that cholinergic afferents to the cortex mediate attentional processes. Rats with selective cholinergic lesions of the nucleus basalis magnocellularis produced by 192 IgG-saporin (SAP) show deficits in attentional performance. These deficits are highly correlated with diminished cholinergic efflux in the infralimbic/prelimbic (IL/PL) cortex during attentional testing. Excitotoxic lesions of the IL/PL in rats trained in an attentional set-shifting task did not impair the initial discimination, a novel discrimination with the previously relevant dimension (intradimensional shift; IDS) or reversal learning, but did impair the ability to shift attention to the previously irrelevant stimulus dimension (extradimensional shifting; EDS). It is not known from the previous study whether the loss of cortical, cholinergic afferents alone would be sufficient to produce the EDS deficit. Consequently, infusions of SAP(0.01 μg/μl; 0.25 μl) were made into either the IL/PL or the orbitofrontal (OF) cortex. Rats were then trained in the same attentional set-shifting task. Subjects had to discriminate between stimuli based on one of two perceptual dimensions, odor or digging media with both dimensions present on all trials. Preliminary analyses show that neither OF nor IL/PL lesions impair the initial discrimination or the IDS. However, IL/PL lesions impair the EDS whereas OF lesions impair reversal learning. These data support dissociable roles of cholinergic afferents to OF and IL/PL in attentional set-shifting.

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

Sarter MF, Draut A, Herzog CD, Bruno JP (2002) Effects of septohippocampal cholinergic deafferentation on attention and learning. Neuroscience 2002 Abstracts 674.8. Society for Neuroscience, Orlando, FL.

Summary: In contrast to the extensively studied attentional functions mediated via basal forebrain corticopetal cholinergic projections, the role of septohippocampal cholinergic projections in attention and memory have remained poorly understood. For example, selective lesions of this system have limited, if any, effects on spatial memory performance. The present experiment initially tested the effects of intraseptal injections of the cholinergic neurotoxin 192-IgG saporin (SAP) on the performance of rats in an operant procedure designed to assess sustained attention. Despite almost complete hippocampal cholinergic deafferentation, the lesioned animals’ attentional performance remained identical to that of controls. Task parameter manipulations designed to further increase the demands on attentional processing also failed to reveal an effect of the lesions. However, lesioned animals were superior in acquiring a version of this task in which the propositional rules of the task were reversed. Lesioned rats achieved >65% hits after 14 training sessions, while intact rats did not reach this level of performance after 50 sessions of training. As the acquisition of the reversal of such extensively practiced response rules suffers from interference from the rather automatic processing of the original rules, loss of hippocampal cholinergic inputs may have reduced the interference that resulted from the processing of the original rules. Thus, hippocampal cholinergic inputs are speculated to modulate, but not to be necessary for, the recall of propositional rules. Collectively, the available data completely dissociate the functions of septo-hippocampal and corticopetal cholinergic projections.

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

Harrell LE, Parsons DS, Conger K, Kolasa K (2002) ß1 adrenergic antagonist effect on brain muscarinic cholinergic receptors. Neuroscience 2002 Abstracts 685.13. Society for Neuroscience, Orlando, FL.

Summary: Degeneration of basal forebrain cholinergic system and sympathetic ingrowth appear to be pathologic changes in Alzheimer’s Disease (AD). An imbalance between these systems may mediate cognitive deficit in AD. To model this situation, 192-IgG-Saporin, a specific cholinergic immunotoxin, was infused intraventricularly to induce cholinergic denervation and sympathetic ingrowth into cortex and hippocampus. After 8 weeks of intraperitoneal injection of Metoprolol, β1 antagonist, at 2.5 mg/kg and 5 mg/kg, the Kd and Bmax of dorsal hippocampus (DH), anterior (AC) and entorhinal (EC) cortex was determined via [3H]-QNB, muscarinic antagonist, binding. Low dose Metoprolol increased Kd in the sympathetic ingrowth, cholinergic denervation, ganglionectomized groups compared to control and vehicle groups (p<.05). Affinity of AC=DH but was > than EC (p<.02). Bmax was greater in AC than DH (p<.05) > than EC (p<.02). Controls and ganglionectomized had > Bmax in AC and EC (p<.03). EC had > Bmax in control and ganglionectomized animals (p<.04). High dose Metoprolol induced a greater affinity in DH>AC>EC (p<.05). No effect was found on Bmax.The results of our study suggest that a β1 antagonist, which is used clinically, can alter the number and affinity of cholinergic receptors, which in turn could potentially alter the AD patients' response to cholinergic therapy.

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

Rudick CN, Gibbs RB, Woolley CS (2002) Estrogen-induced disinhibition of hippocampal CA1 pyramidal cells depends on basal forebrain cholinergic neurons. Neuroscience 2002 Abstracts 740.6. Society for Neuroscience, Orlando, FL.

Summary: Estrogen (E) increases dendritic spine and synapse density on hippocampal pyramidal cells, both in vivo and in vitro. In both cases, the increase in spine/synapse density is preceded by transient disinhibition. Based on in vitro studies, this transient disinhibition is likely to be involved in the mechanism of the subsequent increase in spine density. In adult female rats, where E increases spine/synapse density on CA1 pyramidal cells, it is unknown whether E acts within the hippocampus itself and/or through hippocampal afferents to regulate synaptic changes. Considerable evidence suggests that the basal forebrain (BF) cholinergic system could be involved in mediating E’s effects in the hippocampus. Therefore, we tested the ability of E to disinhibit CA1 pyramidal cells in adult female rats in which BF cholinergic neurons were eliminated by infusion of 192IgG-saporin toxin (SAP) into the medial septum. Two weeks after SAP or SHAM lesion, rats were ovariectomized and treated with E or oil (O) 3 days later. Synaptically evoked inhibitory postsynaptic currents (eIPSCs) and miniature IPSCs (mIPSCs) in CA1 pyramidal cells were evaluated 24h after E or O, the timepoint at which disinhibition occurs. As previously shown, E decreased eIPSC amplitude and mIPSC frequency at 24h. Additionally, E-induced disinhibition was significantly reduced in SAP lesioned rats, but it was not completely blocked. These data demonstrate that the BF cholinergic system is involved in E-induced disinhibition of CA1 pyramidal cells, but that other cells may also be involved.

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

Sherren N, Pappas BA (2002) Neonatal dopamine lesions: Cognitive impairment or hyper-sensitivity to stress. Neuroscience 2002 Abstracts 782.19. Society for Neuroscience, Orlando, FL.

Summary: Neonatal rat pups given a selective cholinergic immunotoxin exhibit large reductions in cortical (30-70%) and hippocampal (75%) choline acetyltransferase (ChAT) activity which persist into adulthood. However these rats do not show spatial learning deficits in the Morris water maze despite the sensitivity of this task to muscarinic receptor blockade and hippocampal damage. We hypothesized that while the developing brain may be able to compensate for early loss of ACh transmission, it may also become more vulnerable to additional disruptions in other systems. We combined postnatal day 7 i.c.v. administration of 192 IgG-saporin with 6-hydroxydopamine (6-OHDA) to lesion either or both ACh and DA terminals respectively. 6-OHDA treatment produced a 90% loss in striatal and a 75% loss in frontocortical DA levels. No differences in exploratory behaviour were found between ACh, DA and ACh/DA lesioned rats. However upon placement in the Morris water maze, DA depleted rats displayed behaviour suggestive of panic and were unable to search for the hidden platform effectively. In order to determine whether the DA depletion was producing a spatial learning deficit or an exaggerated reaction to a stressor (the hidden platform task), a separate cohort of lesioned rats was tested in the cued platform version of the maze. Just prior to testing, the rats received 4 days of shaping in order to gradually habituate them to the pool and teach them the task. Platform location improved in half of the DA and ACh/DA rats, but never approached control or ACh only levels. Thus rats with neonatal DA lesions may be particularly sensitive to stressful tasks. This sensitivity may be partly dependent on lesion extent.

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

Kanold PO, Shatz CJ (2002) Developmental regulation of GABA Receptor subunits requires subplate neurons. Neuroscience 2002 Abstracts 530.11. Society for Neuroscience, Orlando, FL.

Summary: Subplate neurons (SP) are required for formation and patterning of thalamocortical connections. In visual cortex, SP ablation before the onset of the critical period, but when LGN axons are already in layer 4, prevents segregation into ocular dominance columns (ODCs) and emergence of functional orientation columns. Recent studies have linked ODC plasticity with maturation of inhibitory circuitry, which requires the appropriate expression and developmental regulation of GABA receptor subunits. We therefore wondered if SP ablation alters GABA-R subunit expression. Focal injections of kainic acid or immunotoxin were made into cat SP between P7-P10, just prior to the onset of ODC formation. 3 weeks later, in situ hybridization revealed that expression of several subunits of the GABA-A receptor was reduced in the ablated region, especially in layer 4. Other genes involved in synaptic function such as Homer and mGluR subunits also decreased in expression. These changes in gene expression suggest that the efficacy of inhibition in layer 4 is reduced. A reduction in postsynaptic GABA receptors is consistent with previously observed increases in BDNF and GAD expression after SP ablation. These observations imply that SP neurons are essential for the maturation of cortical inhibition, which in turn may be needed for the formation of ODCs and for the functional maturation of thalamocortical connections.

Related Products: ME20.4-SAP (Cat. #IT-15)

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)

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)

Fernandez M, Giuliani A, Giardino L, Calza L (2002) In vivo strategies for stem cells regulation in the adult brain: A chance for cholinergic neurons. Neuroscience 2002 Abstracts 483.14. Society for Neuroscience, Orlando, FL.

Summary: Degenerative diseases represent a severe problem in view of very limited repair capability of nervous system. In order to use stem cells in the adult CNS for repair purpose, we are exploring the possibility to influence, in vivo, proliferation, migration and phenotype lineage of stem cells in adult brain using a growth factor, hormone and cytokine cocktail. In this study we used substances appropriate for in vitro cholinergic differentiation in animals lesioned with icv administration of the cholinergic neurons immunotoxin 195IgG-saporine (3microg/4,5microl). Four months after lesion, no ChAT-positive neurons were found in the basal forebrain, acetylcolinesterase-reactive fibres and ChAT activity in the cerebral cortex and hippocampus dramatically decrease, and animals are severely impaired in water maze learning task. An Alzet osmotic Minipump for chronic release (over 14 days) of the mitogen EGF (360ng/days) was then implanted and connected to a icv catheter. This treatment increases proliferation rate in SVZ in lesioned and unlesioned animals as indicated by the widespread distribution of BrDU-positive nuclei in the forebrain. Rats were then treated with retinoic acid (2.25 mg/day, orally). This treatment reduces Ki67 protein in the SVZ in lesioned rats, and this could indicate a progression toward differentiation. TrkA-positive innervation also increase in the basal forebrain of EGF+retinoic acid treated rats and ChAT activity is lightly, but significantly raises by combined EGF + retinoid acid treatment in the hippocampus.

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

Fargo KN, Sengelaub DR (2002) Androgen manipulation protects remaining motoneurons from dendritic atrophy after induced motoneuron death. Neuroscience 2002 Abstracts 466.13. Society for Neuroscience, Orlando, FL.

Summary: Androgen treatment facilitates axon regrowth after axotomy of facial and sciatic motoneurons, and reverses castration-induced dendritic atrophy in motoneurons of the spinal nucleus of the bulbocavernosus (SNB) in rats. We assessed whether a similar therapeutic effect of androgen would be seen in dendrites following partial depletion of SNB motoneurons. We injected the toxin saporin, conjugated to choleratoxin (β-saporin), unilaterally into the SNB target muscles, bulbocavernosus (BC) and levator ani (LA), of two groups of adult male rats. One group had been castrated six weeks earlier to induce dendritic atrophy, and received testosterone-filled Silastic capsules coincident with β-saporin injection (SAP+T). The other group had no castration or androgen treatment (SAP-only). Four weeks after β-saporin injection, we injected choleratoxin conjugated HRP into the contralateral (non-saporin injected) BC muscle to label SNB motoneurons. A group of untreated normal males was also included. Cell counts were performed, and dendrites of HRP-labeled SNB motoneurons were reconstructed in three dimensions. β-saporin killed ~65% of motoneurons in the SNB ipsilateral to the saporin-injected muscles; contralateral SNB motoneuron numbers were not affected. SNB dendritic arbors on the non-saporin injected side were ~60% shorter in SAP-only animals compared to those of untreated males; in contrast, dendritic arbors in SAP+T animals were unaffected. These results indicate that a) motoneuron death causes dendritic atrophy in remaining SNB motoneurons, and that b) previous castration and concurrent testosterone replacement protects against this atrophy.

Related Products: CTB-SAP (Cat. #IT-14)