sfn2000

McGaughy JA, Dalley JW, Robbins TW, Everitt BJ (2000) The behavioral and neurochemical effects of acute and incremental cholinergic lesions on visual attention during a 5-choice serial reaction time task. Neuroscience 2000 Abstracts 563.1. Society for Neuroscience, New Orleans, LA.

Summary: Previously studies have shown that infusions of 192 IgG-saporin (SAP)into the nucleus basal magnocellularis (nbm) produce severe,persistent impairments in visual attention that correlate with the extent of cortical cholinergic deafferentation. After one bilateral infusion of a low dose (0.15 μg/μl; LX1) of SAP into the nbm, rats performing in a 5 CSRTT show specific behavioral impairments when tested with an increased event rate (ITI=2sec). In vivo microdialysis performed while rats were tested under standard conditions (ITI=5sec) in the 5CSRTT showed that LX1 rats had an increased basal acetylcholine (ACH) efflux in the prefrontal cortex (PFC) relative to sham-lesioned animals on the first day of testing, but no difference in task related efflux on either day of testing. The current study investigated the effects of larger cholinergic lesions on attentional perfomance to determine if they would produce large decreases in cortical ACH efflux and consequently impair attention. Rats were trained in a 5 CSRTT prior to receiving intra-nbm infusions of SAP or vehicle (VEH). Lesioned animals were subjected to repeated infusions of a low dose of the toxin (0.15 μg/μl), a single high dose (0.45 μg/μl) or vehicle. The (0.45 μg/μl) dose of SAP produced profound impairments under baseline conditions that correlated with low levels of ACH efflux in the PFC. These impairments were not attenuated by systemic nicotine or physostigmine. The cumulative lesions were hypothesized to increase sensitivity to attentional demands and pharmacological intervention.

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

Janni G, Moallem T, Lappi DA, Ohara PT, Jasmin L (2000) Schwann cells are removed from the rat spinal cord after effecting recovery from paraplegia. Neuroscience 2000 Abstracts 516.8. Society for Neuroscience, New Orleans, LA.

Summary: Remyelination of the CNS is necessary to restore neural function in a number of demyelinating conditions such as multiple sclerosis. Schwann cells, the myelinating cells of the periphery, are good candidates for this purpose, having more robust regenerative properties than their central homologues, the oligodendrocytes. While the ability of Schwann cells to remyelinate the CNS and effect functional recovery has been demonstrated, their long term survival in the CNS after myelinating central axons is largely unknown. We use saporin conjugated to the cholera toxin B-subunit to demyelinate the rat lumbar spinal cord, remove macroglia, and produce paraplegia. This treatment is followed by a spontaneous proliferation of large numbers of endogenous Schwann cells which remyelinate spinal cord axons with concomitant functional recovery from paraplegia within 75 days. During the following weeks, however, quantification on thin sections shows that Schwann cells are progressively replaced by oligodendrocytes, without any lapse in behavioral recovery. This removal of Schwann cells is confirmed by ultrastructural examination and by immunocytochemistry for Schwann cells and oligodendrocytes. Our results indicate that Schwann cell remyelination of the spinal cord might not be permanent. They can be induced to demyelinate and desheath through endogenous mechanisms that remain to be characterized.

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

Winters BD, Dunnett SB (2000) Combined cholinergic denervation of the hippocampus and posterior cingulate cortex fails to impair working memory performance but may produce deficits in behavioural flexibility in the rat. Neuroscience 2000 Abstracts 563.2. Society for Neuroscience, New Orleans, LA.

Summary: Selective cholinergic denervation of either the hippocampal formation (HPC) or posterior cingulate cortex (pCCX) with the immunotoxin 192 IgG-saporin produces negligible effects on rats’ performance of the delayed nonmatching-to-position (DNMTP) task. Yet, fimbria-fornix transection, which disrupts the cholinergic input to both of these limbic regions, causes a delay-dependent deficit in this working memory task. In the current study, rats were trained in a standard DNMTP procedure and then divided into three groups: Group SAP (n=6) received injections of 192 IgG-saporin into both HPC and pCCX; Group NMDA (n=4) received similar injections of the excitotoxin N-methyl-D-aspartic acid; and Control rats (n=10) received vehicle injections. Following surgery, NMDA rats performed significantly worse than SAP and Control rats at all delays in the DNMTP task (p<0.05); SAP rats did not differ from Controls. All groups then acquired a matching-to-position task (i.e., reversal) over four sessions; however, SAP rats performed significantly more perseverative errors during the first reversal session, resulting in a significant Group x Session interaction (p<0.01). It is suggested that, while the cholinergic projections to the HPC and pCCX are not crucial for working memory performance in the DNMTP task, the cholinergic innervation of these limbic regions may influence behavioural flexibility by modulating a circuit mediating habit-like performance.

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

Blanco-Centurion CA, Salin-Pascual R, Gerashchenko D, Greco MA, Lappi DA, Kilduff TS, Shiromani PJ (2000) DBH-saporin lesions the locus coeruleus, but does not produce cataplexy or abnormal REM sleep triggering. Neuroscience 2000 Abstracts 566.17. Society for Neuroscience, New Orleans, LA.

Summary: Recently, canine narcolepsy was associated with a mutation in the hypocretin-2 receptor (Lin et al., 1999), which binds the neuropeptide hypocretin, also known as orexin. The locus coeruleus receives a very heavy projection of HCRT/OX fibers, and the LC also contains HCRT/OX receptor mRNA. Silence of LC neurons is hypothesized to be key in triggering cataplexy and REM sleep. To test this hypothesis, DBH-saporin was used to selectively lesion the LC. Male Sprague-Dawley rats (400-450 g) instrumented for recording sleep were given DBH-saporin (n=4) (500ng/0.5ul) via a micropipette to the LC. Control rats were administered 192-saporin (n=3), or saline (n=4). Two days later, sleep recordings were obtained for 7 consecutive days. The rat’s behavior was videotaped at night. To identify whether cataplexy was induced, the alpha antagonist, Prazosin was administered (1500h, 500mg/kg, IP) and then sleep and video recordings were made for three hours. Brains were removed for histology. DBH-saporin completely lesioned the LC neurons. However, there were no changes in wakefulness, nonREM or REM sleep. Video recordings also did not reveal any cataplexy episodes. The application of Prazosin did not induce cataplexy or diminish muscle tone in DBH-saporin LC treated rats. Historically, LC lesions have never been found to induce cataplexy. Use of DBH-saporin provides a more specific lesion restricted to the LC neurons where the HCRT/OX receptor mRNA is localized. Our findings indicate that LC neurons are not essential for maintaining muscle tone or wakefulness.

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

Schreihofer AM, Stornetta RL, Guyenet PG (2000) Regulation of sympathetic vasomotor tone and arterial pressure by the rostral ventrolateral medulla after elimination of C1 neurons in rat. Neuroscience 2000 Abstracts 310.7. Society for Neuroscience, New Orleans, LA.

Summary: The rostral ventrolateral medulla (RVLM) tonically stimulates sympathetic preganglionic neurons to maintain arterial pressure (AP). Although the C1 neurons in the RVLM may have a sympathoexcitatory function, it is not known whether they are the essential presympathetic RVLM neurons. In the present study, we selectively destroyed spinally projecting C1 cells (∼84%) with bilateral microinjections (spinal segments T2-T3) of an anti-dopamine-betahydroxylase antibody conjugated to saporin (anti-DβH-SAP). 3-5 weeks later these rats had a normal AP and splanchnic nerve activity (SNA) under chloralose anesthesia. Extracellular recording and juxtacellular labeling of bulbospinal barosensitive neurons in RVLM revealed that after anti-DβH-SAP only the lightly myelinated RVLM neurons with no or very low levels of tyrosine hydroxylase immunoreactivity were preserved. In these rats, inhibition of RVLM (muscimol 100 pmol/100 nl/side) eliminated SNA and decreased AP as seen in control rats. However, treatment with anti-DβHSAP reduced the sympathoexcitatory and pressor responses to electrical stimulation in RVLM. Although treatment with anti-DβH-SAP also eliminated A5 noradrenergic cells, rats with selective lesions of A5 cells (local microinjection of 6-hydroxydopamine) displayed no deficits to stimulation of the RVLM. These data suggest basal sympathetic vasomotor tone relies primarily on non-catecholaminergic presympathetic cells in the RVLM. In contrast, bulbospinal adrenergic neurons are important for the increased SNA and AP produced by stimulation of the RVLM.

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

Ciriello J, Rosas-Arellano MP, Solano-Flores LP (2000) Intrathecal injections of saporin conjugated substance-P alter the development of renal hypertension. Neuroscience 2000 Abstracts 310.2. Society for Neuroscience, New Orleans, LA.

Summary: We have recently shown that there is an up-regulation of mRNA encoding Substance-P (SP) in dorsal root ganglia in the two kidney, one clip (2K1C) model of renal hypertension. In this study, the effect of intrathecal injections of the toxin saporin conjugated to SP (SAP; 5 x 10-6 M) on the development of 2K1C hypertension was investigated in male Wistar rats. Rats were randomly assigned to 2 groups and instrumented with an intrathecal cannula that ended at the T10-T12 spinal level. Arterial pressure (AP) and heart rate (HR) were recorded using the indirect tail-cuff method. After a 1 week control period, one group of animals received a single 10 µl injection of SAP and the other an equal volume of the saline vehicle (control). Two weeks later a clip was placed on the left renal artery in all animals. Injections of either SAP or the vehicle did not alter AP and HR compared to pre-injection levels. In addition, AP and HR were not altered in the SAP group compared to controls for the 2 week period prior to the renal clip. However, during the 4 weeks after the renal clip, AP and HR in the SAP group were significantly lower compared to the control animals. These data suggest that dorsal horn neurons containing SP receptors and that receive afferent renal nerve inputs are involved in renal hypertension.

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

Vulchanova L, Olson TH, Elde R, Honda CN (2000) Role of IB4-binding sensory neurons in the effects of intradermal capsaicin injection. Neuroscience 2000 Abstracts 212.7. Society for Neuroscience, New Orleans, LA.

Summary: We have shown previously that a unilateral injection of a conjugate of the lectin IB4 and the toxin saporin (IB4-SAP) into sciatic nerve of rats results in loss of IB4-binding neurons and transient increase in thermal and mechanical nociceptive thresholds. The thresholds were maximally increased 10 days post-treatment and returned to baseline levels by day 21. In the present study, we examined the responses of IB4-SAP treated rats after intradermal injection of capsaicin, which results in acute nocifensive behavior followed by thermal and mechanical hyperalgesia. The nocifensive behavior of IB4-SAP treated rats 10, 21 and 42 days post-treatment was 6%, 36% and 47%, respectively, of the behavior of control treated rats. IB4-SAP treated rats injected with capsaicin did not develop thermal or mechanical hyperalgesia at any of the time points examined. These results suggest that the increase in thermal nociceptive thresholds after IB4-SAP treatment is due to loss of VR1-expressing IB4-binding neurons since the nocifensive behavior is most likely mediated by the capsaicin receptor VR1, which also transduces noxious thermal stimuli. In addition, VR1 in surviving neurons may contribute to the recovery of thermal nociceptive thresholds. Finally, our results suggest that IB4-binding neurons are required for development of capsaicin-mediated hyperalgesia, and that the recovery of the responsiveness of IB4-SAP treated rats to noxious stimuli under normal conditions is not accompanied by recovery of the mechanisms underlying hyperalgesia.

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

Martin JL, Sloviter RS (2000) Focal hippocampal hyperexcitability after focal interneuron ablation in the rat by substance P-saporin. Neuroscience 2000 Abstracts 389.13. Society for Neuroscience, New Orleans, LA.

Summary: Hyperexcitability after prolonged seizures or head trauma may result from interneuron malfunction or loss; but a causal relationship is in doubt because global insults produce widespread brain damage and other effects. We have therefore sought to destroy interneurons selectively using stable Substance P-saporin (SSPsap; ATS); a neurotoxin internalized by SP receptor (SPR)-expressing neurons. Improved immunofluorescent methods revealed that most GABA-; parvalbumin (PV)-; and somatostatin (SS)-positive (+) cells of all hippocampal regions (dentate gyrus and areas CA1-CA3) are SPR+; but that granule cells; mossy cells; and CA1-3 pyramidal cells are not. Intrahippocampal injections of SSPsap or vehicle were made under urethane anesthesia in 3 sites (20nl/site) of the dorsal hippocampus of 6 male Sprague-Dawley rats/group. After 5-90 days; rats were blindly evaluated in two sites for CA1 pyramidal cell and dentate granule cell responses to perforant path stimulation (PPS). SSPsap-treated rats exhibited relatively normal responses in some sites; but pathophysiology at other sites that was virtually identical to that seen after prolonged PPS or kainate (multiple population spikes and paired-pulse disinhibition in response to 0.1-2.0Hz perforant path (PP) stimuli). Abnormal responses were observed at the earliest time tested (5 days); and at 90 days. Anatomical analysis revealed selective loss of SPR+; PV+; SS+; and GABA+ neurons; and survival of principal cells and extrinsic afferents. Importantly; “epileptic” pathophysiology was observed exclusively in areas of interneuron loss. These data indicate that the pathophysiology produced by status epilepticus or head trauma can be replicated focally by selective interneuron loss alone; and provide the first direct evidence that highly focal interneuron loss per se is capable of replicating “epileptic” disinhibition and hyperexcitability. In addition; the pathophysiology is restricted to the region of the affected interneuron somata; suggesting a highly localized influence of inhibitory interneurons. Supported by: NIH grant NS18201.

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

ATS Poster of the Year Winner. Read the featured article in Targeting Trends.

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)