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Zirbesegger K, Reyes L, Paolino A, Dapueto R, Arredondo F, Gambini JP, Savio E, Porcal W. Molecular Imaging of Monoamine Oxidase A Expression in Highly Aggressive Prostate Cancer: Synthesis and Preclinical Evaluation of Positron Emission Tomography Tracers. ACS Pharmacol Transl Sci 2023; 6:1734-1744. [PMID: 37982127 PMCID: PMC10653014 DOI: 10.1021/acsptsci.3c00175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 10/05/2023] [Accepted: 10/10/2023] [Indexed: 11/21/2023]
Abstract
The role of monoamine oxidase A (MAO-A) in the aggressiveness of prostate cancer (PCa) has been established in recent years. The molecular imaging of MAO-A expression could offer a noninvasive tool for the visualization and quantification of highly aggressive PCa. This study reports the synthesis and preclinical evaluation of 11C- and 18F-labeled MAO-A inhibitors as positron emission tomography (PET) tracers for proof-of-concept studies in animal models of PCa. Good manufacturing practice production and quality control of these radiotracers using an automated platform was achieved. PET imaging was performed in an LNCaP tumor model with high MAO-A expression. The tumor-to-muscle (T/M) uptake ratio of [11C]harmine (4.5 ± 0.5) was significantly higher than that for 2-[18F]fluoroethyl-harmol (2.3 ± 0.7) and [11C]clorgyline (2.0 ± 0.1). A comparable ex vivo biodistribution pattern in all radiotracers was observed. Furthermore, the tumor uptake of [11C]harmine showed a dramatic reduction (T/M = 1) in a PC3 tumor model with limited MAO-A expression, and radioactivity uptake in LNCaP tumors was blocked in the presence of nonradioactive harmine. Our findings suggest that [11C]harmine may serve as an attractive PET probe for the visualization of MAO-A expression in highly aggressive PCa. These radiotracers have the potential for clinical translation and may aid in the development of personalized therapeutic strategies for PCa patients.
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Affiliation(s)
- Kevin Zirbesegger
- Centro Uruguayo de Imagenología Molecular (CUDIM), Ricaldoni 2010, 11600 Montevideo, Uruguay
- Programa de Posgrado, Facultad de Química, Universidad de la República, Av. General Flores 2124, 11800 Montevideo, Uruguay
| | - Laura Reyes
- Centro Uruguayo de Imagenología Molecular (CUDIM), Ricaldoni 2010, 11600 Montevideo, Uruguay
| | - Andrea Paolino
- Centro Uruguayo de Imagenología Molecular (CUDIM), Ricaldoni 2010, 11600 Montevideo, Uruguay
| | - Rosina Dapueto
- Centro Uruguayo de Imagenología Molecular (CUDIM), Ricaldoni 2010, 11600 Montevideo, Uruguay
| | - Florencia Arredondo
- Centro Uruguayo de Imagenología Molecular (CUDIM), Ricaldoni 2010, 11600 Montevideo, Uruguay
| | - Juan P Gambini
- Centro Uruguayo de Imagenología Molecular (CUDIM), Ricaldoni 2010, 11600 Montevideo, Uruguay
| | - Eduardo Savio
- Centro Uruguayo de Imagenología Molecular (CUDIM), Ricaldoni 2010, 11600 Montevideo, Uruguay
| | - Williams Porcal
- Departamento de Química Orgánica, Facultad de Química, Universidad de la República, Av. General Flores 2124, 11800 Montevideo, Uruguay
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Camacho X, Perroni C, Machado CL, de Godoi Carneiro C, de Souza Junqueira M, Faria D, García MF, Fernández M, Oddone N, Benech J, Buchpiguel CA, Cerecetto H, Chammas R, Riva E, Cabral P, Gambini JP. 99mTechnetium- or Cy7-Labeled Fab(Tocilizumab) as Potential Multiple Myeloma Imaging Agents. Anticancer Agents Med Chem 2021; 21:1883-1893. [PMID: 33397271 DOI: 10.2174/1871520621999210104181238] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 10/07/2020] [Accepted: 11/01/2020] [Indexed: 11/22/2022]
Abstract
BACKGROUND Multiple Myeloma (MM) is a malignant hematologic disorder and the second most common blood cancer. Interleukin-6 (IL-6) has been identified as a crucial factor for the proliferation and survival of MM cells and the overexpression of IL-6 receptor is being studied as a molecular target for therapeutic and diagnostic use in myelomas and other comorbidities. Tocilizumab is a humanized monoclonal antibody that binds IL-6R. OBJECTIVE We aim to label and evaluate Fab(Tocilizumab) with 99mTechnetium or Cy7 as potential MM imaging agents. METHODS IL-6R distribution was analyzed by Laser Confocal Microscopy (LCM) in MM cell lines. Fab(Tocilizumab) was produced by the digestion of Tocilizumab with papain for 24h at 37°C, derivatized with NHS-HYNIC-Tfa and radiolabeled with 99mTc. Radiochemical stability and in vitro cell assays were evaluated. Biodistribution and SPECT/CT were performed. Also, Fab(Tocilizumab) was labeled with Cy7 for in vivo fluorescence imaging up to 72h. RESULTS LCM analysis demonstrates IL-6R distribution on MM cell lines. Incubation with papain resulted in complete digestion of Tocilizumab and exhibited a good purity and homogeneity. Radiolabeling with 99mTc via NHS-HYNIC-Tfa was found to be fast, easy, reproducible and stable, revealing high radiochemical purity and without interfering with IL-6R recognition. Biodistribution and SPECT/CT studies showed a quick blood clearance and significant kidney and MM engrafted tumor uptake. Cy7-Fab(Tocilizumab) fluorescent imaging allowed MM1S tumor identification up to 72h p.i. CONCLUSION These new molecular imaging agents could potentially be used in the clinical setting for staging and follow-up of MM through radioactive whole-body IL-6R expression visualization in vivo. The fluorescent version could be used for tissue sample evaluation and to guide surgical excision, if necessary.
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Affiliation(s)
- Ximena Camacho
- Departamento de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la Republica, Montevideo, Uruguay
| | - Carolina Perroni
- Departamento de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la Republica, Montevideo, Uruguay
| | - Camila L Machado
- Nuclear Medicine Medical Investigation Laboratory LIM43-Hospital das Clínicas da Faculdade de Medicina da Universidade de Sao Paulo - HCFMUSP, Sao Paulo, Brazil
| | - Camila de Godoi Carneiro
- Nuclear Medicine Medical Investigation Laboratory LIM43-Hospital das Clínicas da Faculdade de Medicina da Universidade de Sao Paulo - HCFMUSP, Sao Paulo, Brazil
| | - Mara de Souza Junqueira
- Laboratorio de Oncologia Experimental, Faculdade de Medicina, Universidade de Sao Paulo, Av. Dr. Arnaldo Nº 455- Cerqueira Cesar - CEP: 01246903, Sao Paulo, Brazil
| | - Daniele Faria
- Nuclear Medicine Medical Investigation Laboratory LIM43-Hospital das Clínicas da Faculdade de Medicina da Universidade de Sao Paulo - HCFMUSP, Sao Paulo, Brazil
| | - María F García
- Departamento de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la Republica, Montevideo, Uruguay
| | - Marcelo Fernández
- Departamento de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la Republica, Montevideo, Uruguay
| | - Natalia Oddone
- Laboratorio de Senalizacion Celular y Nanobiologia, Instituto de Investigaciones Biologicas Clemente Estable, Montevideo, Uruguay
| | - Juan Benech
- Laboratorio de Senalizacion Celular y Nanobiologia, Instituto de Investigaciones Biologicas Clemente Estable, Montevideo, Uruguay
| | - Carlos A Buchpiguel
- Nuclear Medicine Medical Investigation Laboratory LIM43-Hospital das Clínicas da Faculdade de Medicina da Universidade de Sao Paulo - HCFMUSP, Sao Paulo, Brazil
| | - Hugo Cerecetto
- Departamento de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la Republica, Montevideo, Uruguay
| | - Roger Chammas
- Laboratorio de Oncologia Experimental, Faculdade de Medicina, Universidade de Sao Paulo, Av. Dr. Arnaldo Nº 455- Cerqueira Cesar - CEP: 01246903, Sao Paulo, Brazil
| | - Eloisa Riva
- Clinica Hematologica. Hospital de Clinicas. Facultad de Medicina. Universidad de la Republica, Montevideo, Uruguay
| | - Pablo Cabral
- Departamento de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la Republica, Montevideo, Uruguay
| | - Juan P Gambini
- Centro de Medicina Nuclear e Imagenologia Molecular, Hospital de Clinicas, Facultad de Medicina, Universidad de la Republica, Montevideo, Uruguay
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Dapueto R, Aguiar RB, Moreno M, Machado CML, Marques FLN, Gambini JP, Chammas R, Cabral P, Porcal W. Technetium glucose complexes as potential cancer imaging agents. Bioorg Med Chem Lett 2015; 25:4254-9. [PMID: 26318991 DOI: 10.1016/j.bmcl.2015.07.098] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 07/26/2015] [Accepted: 07/29/2015] [Indexed: 11/30/2022]
Abstract
GLUT's (facilitative glucose transporters) over-expression in tumor cells has allowed the detection of several cancer types, using a glucose analogue ((18)F-FDG) with PET images, worldwide. New glucose analogs radiolabeled with (99m)Tc could be a less-expensive and more accessible alternative for diagnosis using SPECT imaging. d-Glucose ((99m)Tc-IDAG) and 2-d-deoxyglucose ((99m)Tc-AADG) organometallic complexes were proposed and studied as potential (18)F-FDG surrogates. The glucose complexes were prepared and evaluated as potential cancer imaging agents, in a melanoma tumor model. Iminodiacetic acid (IDA) and aminoacetate (AA) moieties were chosen as chelating system for radiolabeling with (99m)Tc. Tumor uptake of the formed complexes was evaluated in B16 murine cell line in vitro and in vivo in melanoma bearing C57BL/6 mice. In vitro and in vivo studies were conducted with (18)F-FDG in order to compare the uptake of (99m)Tc-glucose complexes in the tumor model. IDAG and AADG compounds were synthesized and radiolabeled with (99m)TcO4(-) to obtain the (99m)Tc-IDAG and (99m)Tc-AADG complexes in high yield and stability. In vitro cell studies showed maximum uptake at 60 min for complexes, (99m)Tc-IDAG and (99m)Tc-AADG, with 6% and 2%, respectively. Biodistribution studies showed high tumor uptake one hour post-injection, reaching tumor-to-muscle ratios of 12.1 ± 3.73 and 2.88 ± 1.40 for (99m)Tc-IDAG and (99m)Tc-AADG, respectively. SPECT and micro-SPECT-CT images acquired after the injection of (99m)Tc-IDAG showed accumulation in tumor sites, suggesting that this glucose complex would be a promising candidate for cancer imaging.
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Affiliation(s)
- Rosina Dapueto
- Laboratorio de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la República, Mataojo 2055, 11400 Montevideo, Uruguay; Grupo de Química Medicinal, Laboratorio de Química Orgánica, Facultad de Ciencias-Facultad de Química, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay
| | - Rodrigo B Aguiar
- Centro de Investigação Translacional em Oncologia, Instituto do Câncer do Estado de São Paulo, Av. Dr. Arnaldo, 251, São Paulo 01246-903, Brazil
| | - María Moreno
- Departamento de Desarrollo Biotecnológico, Instituto de Higiene, Facultad de Medicina, Universidad de la Republica, Av. Alfredo Navarro 3051, 11600 Montevideo, Uruguay
| | - Camila M L Machado
- Centro de Medicina Nuclear, Faculdade de Medicina, Universidade de São Paulo, Trav. R. Dr. Ovidio Pires de Campos s/n, São Paulo 05403-010, Brazil
| | - Fabio L N Marques
- Centro de Medicina Nuclear, Faculdade de Medicina, Universidade de São Paulo, Trav. R. Dr. Ovidio Pires de Campos s/n, São Paulo 05403-010, Brazil
| | - Juan P Gambini
- Centro de Medicina Nuclear, Hospital de Clínicas, Facultad de Medicina, Universidad de la Republica, Av Italia s/n, 11600 Montevideo, Uruguay
| | - Roger Chammas
- Centro de Investigação Translacional em Oncologia, Instituto do Câncer do Estado de São Paulo, Av. Dr. Arnaldo, 251, São Paulo 01246-903, Brazil
| | - Pablo Cabral
- Laboratorio de Radiofarmacia, Centro de Investigaciones Nucleares, Facultad de Ciencias, Universidad de la República, Mataojo 2055, 11400 Montevideo, Uruguay.
| | - Williams Porcal
- Grupo de Química Medicinal, Laboratorio de Química Orgánica, Facultad de Ciencias-Facultad de Química, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay.
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Dapueto R, Fernández M, Aguiar R, Moreno M, Machado C, Marques F, Gambini JP, Chammas R, Cabral P, Porcal W. Biological evaluation of two glucose derivatives radiolabeled with 99mTc as potential cancer imaging agents. Nucl Med Biol 2014. [DOI: 10.1016/j.nucmedbio.2014.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Choudhury PS, Savio E, Solanki KK, Alonso O, Gupta A, Gambini JP, Doval D, Sharma P, Dondi M. (99m)Tc glucarate as a potential radiopharmaceutical agent for assessment of tumor viability: from bench to the bed side. World J Nucl Med 2013; 11:47-56. [PMID: 23372437 PMCID: PMC3555394 DOI: 10.4103/1450-1147.103405] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Several radiotracers have been used for assessing cell death, whether by necrosis or apoptosis. 99mTc glucarate, which has initially been reported to be concentrating/accumulating in myocardial infarction or zones of cerebral injury, has also shown some tumor-seeking properties in a few preliminary studies. Under International Atomic Energy Agency (IAEA)'s coordinated research program, we report here the standardization, quality control, and clinical evaluation (detection, evaluation of response, and comparison with 18F Fluorodeoxyglucose) of this tracer in well-characterized lung cancer and head neck malignancies in a single-arm prospective observational study. Forty-seven patients (29 inoperable lung carcinoma and 18 head and neck malignancies) were prospectively enrolled and underwent 99mTc glucarate imaging [whole body planar and single-photon emission computed tomography of the region of interest] 4-5 hours after injection of 20 mCi of the radiopharmaceutical. Excellent 99mTc glucarate concentration was noted in the target lesion in lung cancer and head and neck malignancies. The sensitivity was found to be better in lung cancer. Avid concentration of tracer was seen in the metastatic sites. During response evaluation, the glucarate concentration correlated well with the clinical and other radiological findings. 99mTc glucarate showed avid concentration of tracer in the tumor, suggesting it to be a potential tumor imaging agent which can be used for detection and assessment of therapeutic response in malignancy.
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Affiliation(s)
- Partha S Choudhury
- Department of Nuclear Medicine, Rajiv Gandhi Cancer Institute and Research Center, New Delhi, India
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Tassano MR, Audicio PF, Gambini JP, Fernandez M, Damian JP, Moreno M, Chabalgoity JA, Alonso O, Benech JC, Cabral P. Development of 99mTc(CO)3-dendrimer-FITC for cancer imaging. Bioorg Med Chem Lett 2011; 21:5598-601. [DOI: 10.1016/j.bmcl.2011.06.079] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2011] [Revised: 06/15/2011] [Accepted: 06/17/2011] [Indexed: 01/31/2023]
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Gambini JP, López Lerena JJ, Quagliata A, Hermida JC, Heuguerot C, Alonso O. 99mTc-HYNIC octreotide in neuroblastoma. Ann Nucl Med 2008; 22:817-9. [DOI: 10.1007/s12149-008-0201-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Accepted: 07/30/2008] [Indexed: 10/21/2022]
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Quagliata A, López JJ, Guissoli P, Gambini JP, Hermida JC, Alonso O. Dobutamine modulated Tc-99m MIBI scintigraphy in secondary hyperparathyroidism in uremic patients. Clin Nucl Med 2007; 32:782-6. [PMID: 17885358 DOI: 10.1097/rlu.0b013e318148aff3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The aim of this study was to determine if low-dose dobutamine infusion can enhance Tc-99m methoxy isobutyl isonitrile (MIBI) uptake of hyperfunctioning parathyroid glands of patients with secondary hyperparathyroidism (SHP). We studied 24 patients with chronic renal failure and SHP. Median age of the sample was 47.5 years. A single-tracer, double-phase technique was performed, acquiring planar images of the neck and thorax after the injection of 740 to 1110 MBq (20-30 mCi) of Tc-99m MIBI. After 2 to 7 days, the study was repeated after the infusion of low-dose dobutamine of 2.0 microg . kg . min for 60 minutes. The scan was considered positive for hyperfunctioning parathyroid tissue when an area of increased uptake that persisted on late imaging was found. Parathyroid-to-thyroid count rates (PT/T) were calculated for each abnormal focus. Hyperplasic parathyroid tissue was confirmed in 12 of 24 patients who underwent neck surgery whereas the remaining group had persistent or worsening disease, verified by clinical follow-up between 6 and 25 months after the nuclear studies (median: 12 months). An MIBI baseline study was positive in 21 of 24 patients (87%), whereas the dobutamine study was positive in all patients. Thirty-five abnormal foci were seen on baseline MIBI studies and 43 on dobutamine scans (1.46 +/- 1.02 vs. 1.79 +/- 0.88, mean +/- SD, respectively, P = 0.043). Dobutamine PT/T ratios were significantly higher than those from the baseline study (1.49 +/- 0.30 vs. 1.38 +/- 0.28, mean +/- SD, respectively, P = 0.0002, n = 43). We concluded that low-dose dobutamine Tc-99m MIBI scintigraphy has the potential of enhancing tracer uptake and retention in patients with SHP.
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Affiliation(s)
- Adriana Quagliata
- Nuclear Medicine Center of the Clinical Hospital, University of Uruguay, Montevideo, Uruguay
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Pedemonte M, Gambini JP, Velluti RA. Novelty-induced correlation between visual neurons and the hippocampal theta rhythm in sleep and wakefulness. Brain Res 2005; 1062:9-15. [PMID: 16248987 DOI: 10.1016/j.brainres.2005.07.069] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2005] [Revised: 07/29/2005] [Accepted: 07/29/2005] [Indexed: 10/25/2022]
Abstract
Various rhythms have been shown to affect sensory processing such as the waking-sleep cycle and the hippocampal theta waves. Changes in the firing of visual lateral geniculate nucleus neurons have been reported to be dependent on the animal's behavioral state. The lateral geniculate extracellular neuronal firing and hippocampal field activity were recorded in chronically implanted animals to analyze the relationship during quiet wakefulness and sleep associated with stimulation shifts that may introduce novelty. During wakefulness, a change in light flash stimulation pattern (stimuli frequency shift, stimuli on and off) caused an increment in the theta band power in 100% of the cases and a phase-locking of the spikes in 53% of the recorded neurons. During slow wave sleep, there were no consistent changes in the theta power notwithstanding 13% of the neurons exhibited phase-locking, i.e., novelty may induce changes in the temporal correlation of visual neuronal activity with the hippocampal theta rhythm in sleep. The present results suggest that visual processing in slow wave sleep exists, while auditory information and learning were reported during slow wave sleep in animals and newborn humans. The changes in the theta power as well as in the neuronal phase-locking amount indicate that in slow wave sleep, the ability of the hippocampus to detect/process novelty, although present, may be decreased. This is consistent with the noticeable decrease in awareness of the environment during sleep.
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Affiliation(s)
- Marisa Pedemonte
- Neurofisiología, Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Ave. General Flores 2125, 11800 Montevideo, Uruguay.
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Abstract
The hippocampal theta rhythm (theta) was reported to be associated with movements, attention, auditory processing, autonomic functions, learning and memory and postulated as an associator of discontiguous events. Since visual information includes temporal cues, our study was centered on the correlation between hippocampal theta rhythm and lateral geniculate activity. Phase relationships between hippocampal theta and unit firing were found with both spontaneous and light evoked activity during wakefulness, slow wave and paradoxical sleep. This temporal correlation was dynamic, exhibiting changes related to the sleep-waking cycle and perhaps to attention shifts. Hippocampal theta rhythm may supply a low frequency temporal dimension to the processing of visual information.
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Affiliation(s)
- Juan P Gambini
- Neurofisiología, Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Av. Gral. Flores 2125, 11800 Montevideo, Uruguay
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Pedemonte M, Barrenechea C, Nuñez A, Gambini JP, García-Austt E. Membrane and circuit properties of lateral septum neurons: relationships with hippocampal rhythms. Brain Res 1998; 800:145-53. [PMID: 9685619 DOI: 10.1016/s0006-8993(98)00517-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The lateral septum receives the most important afferents from the hippocampus, has been proposed to contribute to theta (theta) rhythm generation. Our aim was to study the membrane and circuital properties of lateral septum neurons and their relationship with hippocampal rhythms. Extra- and intracellular recordings (n=81) were obtained in urethane-anesthetized rats. Two neuronal populations were found, one of them with hippocampal theta; rhythm dependence (theta-D, 68%), and the other group independent of hippocampal theta; rhythm (theta-I, 32%). Other differences were spontaneous firing rate (theta-D=13.20+/-2.09, theta-I=6.99+/-1.18; p<0.005) with a bursting pattern in the theta-D group and single discharges in the theta-I group. Intracellular recordings showed higher synaptic activity in theta-D than in theta-I neurons. Both groups showed fast spikes while only theta-D neurons had high-threshold and low-threshold slow spikes. theta-D neurons had theta-oscillations in their membrane potential. Stimulation of the contralateral lateral septum resets the hippocampal theta rhythm and the theta rhythm recorded intracellularly in the lateral septum neurons. Some neurons (10.6%) showed rhythmic oscillations lasting a few seconds, at a higher frequency than those of the simultaneously recorded hippocampal EEG. This high frequency appeared spontaneously or could be evoked by stimulations of the fornix and reticularis pontis oralis nucleus (RPO). Homologous high frequency oscillations appeared in the simultaneously recorded hippocampal EEG, synchronized with the neuronal activity, during fornix stimulation. RPO stimulation evoked increments (57%) or decrements (43%) in the firing rate of lateral septum neurons. Thus, they could participate in different septal networks to modulate the theta rhythm. The marked functional relationship between lateral septum neurons and hippocampal theta rhythm supports the proposal that lateral septum represents a feedback system for the improvement of medial septum theta rhythm. The hypothalamic projections could be a way to introduce theta and higher rhythms into this structure that control many biological rhythms.
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Affiliation(s)
- M Pedemonte
- Neurofisiología, Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Av. Gral. Flores 2125, 11800 Montevideo, Uruguay.
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