sfn2001

Wang H, Guyenet PG (2001) DL-homocysteic (DLH)-induced tachypnea is eliminated by ablation of neurokinin-1 receptor immunoreactive (NK1R-ir) neurons of the preBötzinger complex (preBötc). Neuroscience 2001 Abstracts 633.4. Society for Neuroscience, San Diego, CA.

Summary: We identified a hot spot of the ventrolateral medulla (VLM) where tachypnea is produced by small injections of the excitatory amino acid DLH in urethane-anesthetized vagotomized rats. We sought to determine its anatomical location relative to a group of NK1R-ir cells that may be a marker of the preBötC. We also determined the location of the hot spot relative to VLM pressor and depressor sites. The VRG was located by recording respiratory units and then 5-10 nl of 10 mM DLH were injected into the VRG at 200 mm interval from Bregma -12.1 to -13.3 mm. DLH produced site-specific changes in respiratory rate and mean arterial blood pressure (MAP). At rostral levels (Bregma -12.1 mm) PND rate decreased and MAP increased (-57 ± 11% and 9.4 ± 0.9%; N= 4-6). At more caudal levels these effects gradually reversed (cross-over point at -12.4 mm). Tachypneic responses were restricted between Bregma -12.5 and -13.1 mm with a sharp peak (88.7 ± 12.8% increase in rate) at -12.7 mm. The hot spot corresponded to where most pre-inspiratory neurons are found. It overlapped with VRG NK1R-ir cells but was more restricted than the distribution of these cells. Depressor responses were maximal at -12.7 mm and stable at more caudal levels. After unilateral ablation of the NK1R-ir cells (N=3) with a saporin-NK1R agonist conjugate, the DLH-induced tachypnea disappeared bilaterally. In conclusion, the tachypnea hot spot corresponds to the defined preBötC. It overlaps with the rostral end of the VLM depressor area and the NK1R-ir neurons of the preBötC may be responsible for DLH-induced tachypnea.

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

Motooka Y, Kondoh T, Nomura T, Tamaki N, Nishizaki T (2001) Poster: Selective cholinergic denervation inhibits expression of long-term potentiation in the adult but not infant rat hippocampus. Neuroscience 2001 Abstracts 599.7. Society for Neuroscience, San Diego, CA.

Summary: The present study assessed the role of the cholinergic systems on the expression of perforant path long-term potentiation (LTP) in rat hippocampal slices from the infant and adult brain. To denervate the cholinergic systems, 192 1gG-saporin was injected into the lateral ventricle of the infant (2 weeks old) and adult (6 weeks old) rat brain. There, choline acetyltransferase immunoreactive fibers were little detectable two weeks and two months after injection for both the groups. For the infant rats, perforant path LTP was not affected by selective cholinergic denervation; the probability of LTP development was 0.83 (5/six slices) and 0.78 (7/nine slices) at 2 weeks and 2 months later in 192 IgG-saporin-treated slices, as compared with 0.83 at each period in control saline-treated slices. In contrast, the expression of the LTP was blocked by selective cholinergic denervation for the adult rats; the probability of LTP development was 0 (0/ten slices) and 0.38 (3/eight slices) at 2 weeks and 2 months later in 192 IgG-saporin-treated slices, as compared with 0.8 (8/ten slices) and 0.83 (5/six slices) at each period in control saline-treated slices. The results of the present study thus suggest that the cholinergic systems play a crucial role in the expression of LTP in the adult brain and that the denervated systems in the infant brain could be compensated by the sprouting of non-cholinergic fibers.

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

Peterson WE, Jordan LM, Brownstone RM (2001) Immunolesioning of identified motoneuron pools following intramuscular injection of the immunotoxin, 192-IgG-saporin, in neonatal rats. Neuroscience 2001 Abstracts 626.14. Society for Neuroscience, San Diego, CA.

Summary: Studies have shown that the immunotoxin, 192-IgG-Saporin, can selectively lesion p75-positive cholinergic neurons of the basal forebrain in adult rats. Here we demonstrate the novel use of 192-IgG-Saporin to induce MN loss following intramuscular (I.M.) injection in neonatal rats. Two days following I.M. injection of 192-IgG-Cy3, neonatal rats (but not adult rats or neonatal mice) had Cy3-labeled MNs. This suggests that the 192-IgG antibody and its conjugates can be internalised by receptor-mediated endocytosis and retrogradely transported to spinal motor neurons. To induce MN loss, the left hind limb musculature of anaesthetised Sprague-Dawley rats were exposed, and several muscles injected with 0.5μg of 192-IgG-Saporin (Chemicon). Right hind-limb muscles were injected with DiI. Animals were sacrificed 25 days later. Ten μm coronal sections were obtained using a cryostat and Nissl stained. The neonatal rats showed signs of a locomotor deficit 2.5 weeks post injection with 192-IgG-Saporin, which increased slightly in severity over the next week and a half. Nissl stained coronal sections of the lumbar region showed an obvious MN deficit on the 192-IgG-Saporin treated side compared to control side. The injected muscles were also severely atrophic, a not unexpected finding given that they too express p75 receptors. We conclude that 192-IgG-Saporin can be used to lesion MN pools when IM injected in neonatal rats. This model may prove useful for testing cell replacement therapies for the treatment of MN diseases like amyotrophic lateral sclerosis (ALS).

Related Products: 192-IgG Mouse Monoclonal, Cy3-labeled (Cat. #AB-N43FL3)

Kudoh M, Seki K, Watanabe S, Shibuki K (2001) Sound sequence discrimination requires cholinergic inputs and suppression of M-currents in the rat auditory cortex. Neuroscience 2001 Abstracts 621.2. Society for Neuroscience, San Diego, CA.

Summary: Synaptic potentiation after sequential heterosynaptic stimulation is dependent on the stimulus sequence in the auditory cortex. Atropine or antagonists of M1 receptors block this sequence dependence. However, it is rescued by linopirdine, an inhibitor of M-currents, even in the presence of atropine. In the present study, we investigated the role of cholinergic inputs and the resulting suppression of M-currents in sound sequence discrimination. Rats were trained to discriminate sequence of two sounds. Licking a spout during sound presentation of a particular sequence was rewarded with water. The sounds of the rewarded or unrewarded sequence were randomly presented in a trial, which was repeated every one minute for 12 hours in 4 days. The percentage of the trials with a licking response to sounds was calculated separately for the rewarded and unrewarded sequence. Test performance, estimated from the difference, was significantly increased in the 4 days. Atropine (10 mg/Kg, i.p.) suppressed the increase of test performance. A cholinergic immunotoxin, 192IgG-saporin, was injected into the auditory cortex (62-400 ng/1µl) 1 week before the test. Sound sequence discrimination, but not discrimination between the two sounds, was significantly suppressed in these rats. Linopirdine (5 mg/Kg, i.p.) rescued the test performance of sound sequence discrimination in the rats injected with 192IgG-saporin. These results suggest that sound sequence discrimination requires cholinergic inputs and the resulting suppression of M-currents in the auditory cortex.

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

Nattie EE, Li A (2001) Destruction by SP-SAP of rat retrotrapezoid nucleus (RTN) neurons expressing the neurokinin 1 receptor (NK1R) decreases breathing at rest and in response to hypercapnia. Neuroscience 2001 Abstracts 573.1. Society for Neuroscience, San Diego, CA.

Summary: Neurons in the RTN are hypothesized to provide both a tonic excitation for breathing and one location for central chemoreception (see Nattie, E., Prog. Neurobiol.1999). Lesions in anesthetized animals support the former while both lesions and focal acidification in unanesthetized animals support the latter. Application of substance P (SP) in the RTN increases respiratory output and immunohistochemistry for the SP (NK1) receptor shows extensive staining in the RTN. To destroy specifically these RTN neurons with NK1Rs we injected unilaterally in the RTN of the rat SP conjugated to the ribosomal toxin, saporin (SP-SAP; 100 nl; 1 uM; Advanced Targeting Systems). We measured ventilation by whole body plethysmography in the unanesthetized rat. At 6 to 15 days following SP-SAP injection, ventilation during air breathing was reduced by 19 to 24% and the response to 7% CO2 inhalation was reduced by 22 to 30%. Subsequent immunohistochemistry showed dramatically reduced NK1R staining in the area of the SP-SAP injection, which is difficult to quantify given the small number of RTN neurons and the extensive NK1R distribution along neuronal processes. RTN neurons with NK1Rs provide both a tonic excitation for breathing and a portion of the response to systemic hypercapnia.

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Butt AE, Noble MM, Barrett H, Brinegar S, Hixon A, Kester B, Levey D, Rea T, Ryan M, Schulze S, Vogel L (2001) 192 IgG saporin lesions of the nucleus basalis magnocellularis impair working but not reference memory in a delayed non-match-to-position y-maze task. Neuroscience 2001 Abstracts 314.17. Society for Neuroscience, San Diego, CA.

Summary: The current experiment tests the hypothesis that the cortically projecting cholinergic neurons of the nucleus basalis magnocellularis (NBM) are selectively involved in working and not reference memory. Male Long-Evans rats received extensive pre-operative training in a delayed non-match-to-position (DNMTP) task in a Y-maze. In this task, 0-s, 1-min, or 2-min delays were interposed between consistently food-reinforced “sample runs”, where rats were allowed access to only one arm of the maze, and “choice runs”, where rats were allowed access to both arms of the maze but were reinforced only for entering the arm opposite that entered on the previous sample run. Upon completion of pre-operative training, rats were matched for performance and were randomly assigned to a sham lesion group or to the NBM lesion group, which received bilateral infusions of the cholinergic immunotoxin 192 IgG-saporin into the NBM. As predicted, post-operative performance in the NBM lesion group was normal at the 0-s delay but was severely impaired at the 1-min and 2-min delays. Results suggest that the NBM is critically involved in supporting normal spatial working memory but that previously acquired reference memory for the non-matching rule remains intact following selective NBM lesions.

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

Estacio MA, Tsukamura H, Reyes BA, Maeda KI (2001) Noradrenergic inputs to the paraventricular nucleus (PVN) is involved in estrogen receptor α expression in the PVN of 48-h fasted and 2DG-injected female rats. Neuroscience 2001 Abstracts 409.6. Society for Neuroscience, San Diego, CA.

Summary: Involvement of noradrenergic inputs to the paraventricular nucleus (PVN) in estrogen receptor α (ERα) expression in the PVN during 48-h fasting and 2DG-induced glucoprivation in female rats was determined by examining the effect of destroying the noradrenergic inputs to the PVN using the saporin-conjugated anti-dopamine-β-hydroxylase (anti-DBH-saporin). Ovariectomized rats were injected bilaterally with anti-DBH-saporin in the PVN. After two weeks, animals were either fasted for 48 hours or injected intravenously with 2DG, then perfused with 4% paraformaldehyde. Brain sections were processed for ERα and DBH immunocytochemistry. Forty-eight-hour fasting or 2DG injection siginificantly increased the number of ERα-immunoreactive (ERα-ir) cells in the PVN in control animals. Anti-DBH-saporin injection prevented fasting- or 2DG-induced increase in ERα-ir cells in the PVN. The DBH-ir axons in the parvocellular PVN were severely reduced following anti-DBH-saporin injection in both fasted and 2DG injected rats. Among the brainstem noradrenergic cell groups examined, there was a significant decrease in the number of DBH-ir cells in the A2 region of both fasted and 2DG injected rats treated with anti-DBH-saporin. There was no obvious reduction in the number of DBH-ir cells in the A1 and A6 regions in the anti-DBH-saporin-injected fasted- or 2DG-injected rats. The results suggest that the A2 noradrenergic input to the PVN plays a major role in increasing ERα expression in the PVN in response to 48-h fasting or 2DG-induced glucoprivation.

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Wiley RG, Kline IV RH, Lappi DA (2001) Dose-dependent effects of intrathecal substance P-saporin and SSP-saporin. Neuroscience 2001 Abstracts 281.11. Society for Neuroscience, San Diego, CA.

Summary: Selective destruction of lamina I dorsal horn neurons expressing the neurokinin-1 receptor (NK-1R) can attenuate responses to capsaicin injection and thermal hyperalgesia/mechanical allodynia in models of inflammatory, persistent or neuropathic pain. In the present study, we sought to determine the relationships between spinal intrathecal dose of substance P-saporin or the related toxin, SSP-saporin, the loss of NK-1R neurons and reduction of phase II formalin responses. Rats were injected intrathecally with 10 ul of either vehicle, 175 ng, 350 ng or 700 ng of SP-sap. Others were injected with either vehicle, 25 ng, 50 ng or 100 ng of SSP-sap. After 2 weeks, nocifensive behavior was scored for 90 min after a unilateral hindpaw injection of dilute formaldehyde. The amount of phase II nocifensive behavior from 20-90 min post injection was totaled for each animal. Rats were sacrificed and transverse lumbosacral spinal cord sections were stained for NK-1R using indirect immunoperoxidase technique. Digital micrographs of the superficial dorsal horn were captured and the number of pixels in the darkest intensity values were expressed as percent of the analysis area for each dorsal horn. Significant correlations were noted for dose vs dark pixel percentage and for dark pixel percentage vs phase II formalin behavior. The greater the toxin dose the greater the loss of NK-1R staining and the greater the attenuation of phase II formalin behavior. These results indicate that the toxin effects on pain behavior are proportional to the degree of loss of lamina I NK-1R expressing neurons.

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Savage LM, Buzzette R, Ramirez D (2001) The role of the cholinergic basal forebrain in learning, memory and reward expectancies. Neuroscience 2001 Abstracts 314.18. Society for Neuroscience, San Diego, CA.

Summary: The cholinergic basal forebrain degenerates in Alzheimer’s Disease and the degree of this degeneration correlates with a decline in cognitive processing. In the present study we have modeled this degeneration in the rat by the selective immunotoxin 192 IgG-Saporin. This immunotoxin destroys cholinergic neurons in the basal forebrain nuclei in rats and thus allows for the study of the impact of cholinergic deafferentation on learning, memory, and other cognitive processes without direct effects on other neuronal systems. After intracerebroventricularly infusions of the immunotoxin or vehicle solution, male rats were allowed to recover for three weeks before being tested in a matching-to-position task. The matching-to-position task was altered to influence the type of cognitive strategies a subject would use to solve the task. The main behavioral manipulation was the use of the differential outcome procedure (DOP). The DOP involves correlating each to-be-remembered event with a distinct reward condition. We found that cholinergic lesions did not dramatically impair learning the matching rule. However, the memory performance of subjects with cholinergic lesions was dramatically impaired – if subjects were not trained with the DOP. When subjects were trained with the DOP, and relied on reward expectancies to solve the delayed-matching-to-position task the cholinergic lesion had little effect. These findings demonstrate that cholinergic immunolesions by 192IgG-saporin induce specific cognitive impairments—dependent on task demand characteristics.

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Hamaue N, Yamazaki Y, Ohmori H, Sumikawa K (2001) Nicotine enhances N-methyl-D-aspartate receptor responses and facilitates long-term potentiation in the hippocampus from rats with cholinergic lesions. Neuroscience 2001 Abstracts 376.5. Society for Neuroscience, San Diego, CA.

Summary: Nicotine reverses cognitive impairments caused by lesion of the cholinergic system and improves performance of Alzheimer’s patients. The mechanisms underlying these effects of nicotine, however, are unknown. Because nicotine facilitates the induction of N-methyl-D-aspartate receptor (NMDAR)-dependent long-term potentiation (LTP) in the hippocampal CA1 region, we examined whether nicotine enhances NMDAR responses and facilitates LTP induction in the hippocampus from rats with cholinergic lesions. Selective cholinergic denervation of rat hippocampus was performed by the immunotoxin 192 IgG-saporin. We then recorded burst NMDAR responses in hippocampal slices prepared from 192-IgG-saporin-treated rats and found that nicotine (1 μM) enhanced burst NMDAR responses. When GABAergic transmission was completely blocked by picrotoxin, nicotine had no effect on burst NMDAR responses. We also monitored the induction of LTP in 192-IgG-saporin-treated hippocampi and found that a weak tetanus (20 pulses at 100 Hz), which induced LTP in PBS-treated hippocampi, failed to induced LTP. However, in the presence of nicotine (1 μM), a same weak tetanus induced LTP in 192-IgG-saporin-treated hippocampi. Our results suggest that nicotine potentiates NMDAR responses by disinhibition of pyramidal cells and facilitates LTP induction in the hippocampus from animals with cholinergic lesions. The observed nicotine effects may represent the cellular mechanism underlying the compensatory action of nicotine in the presence of cholinergic deficits.

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