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Lolansen SD, Barbuskaite D, Ye F, Xiang J, Keep RF, MacAulay N. Spontaneously hypertensive rats can become hydrocephalic despite undisturbed secretion and drainage of cerebrospinal fluid. Fluids Barriers CNS 2023; 20:53. [PMID: 37403103 DOI: 10.1186/s12987-023-00448-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 06/01/2023] [Indexed: 07/06/2023] Open
Abstract
BACKGROUND Hydrocephalus constitutes a complex neurological condition of heterogeneous origin characterized by excessive cerebrospinal fluid (CSF) accumulation within the brain ventricles. The condition may dangerously elevate the intracranial pressure (ICP) and cause severe neurological impairments. Pharmacotherapies are currently unavailable and treatment options remain limited to surgical CSF diversion, which follows from our incomplete understanding of the hydrocephalus pathogenesis. Here, we aimed to elucidate the molecular mechanisms underlying development of hydrocephalus in spontaneously hypertensive rats (SHRs), which develop non-obstructive hydrocephalus without the need for surgical induction. METHODS Magnetic resonance imaging was employed to delineate brain and CSF volumes in SHRs and control Wistar-Kyoto (WKY) rats. Brain water content was determined from wet and dry brain weights. CSF dynamics related to hydrocephalus formation in SHRs were explored in vivo by quantifying CSF production rates, ICP, and CSF outflow resistance. Associated choroid plexus alterations were elucidated with immunofluorescence, western blotting, and through use of an ex vivo radio-isotope flux assay. RESULTS SHRs displayed brain water accumulation and enlarged lateral ventricles, in part compensated for by a smaller brain volume. The SHR choroid plexus demonstrated increased phosphorylation of the Na+/K+/2Cl- cotransporter NKCC1, a key contributor to choroid plexus CSF secretion. However, neither CSF production rate, ICP, nor CSF outflow resistance appeared elevated in SHRs when compared to WKY rats. CONCLUSION Hydrocephalus development in SHRs does not associate with elevated ICP and does not require increased CSF secretion or inefficient CSF drainage. SHR hydrocephalus thus represents a type of hydrocephalus that is not life threatening and that occurs by unknown disturbances to the CSF dynamics.
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Affiliation(s)
- Sara Diana Lolansen
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3B, Copenhagen, DK-2200, Denmark
| | - Dagne Barbuskaite
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3B, Copenhagen, DK-2200, Denmark
| | - Fenghui Ye
- Department of Neurosurgery, University of Michigan, Ann Arbor, USA
| | - Jianming Xiang
- Department of Neurosurgery, University of Michigan, Ann Arbor, USA
| | - Richard F Keep
- Department of Neurosurgery, University of Michigan, Ann Arbor, USA
| | - Nanna MacAulay
- Department of Neuroscience, University of Copenhagen, Blegdamsvej 3B, Copenhagen, DK-2200, Denmark.
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Hao X, Ye F, Holste KG, Hua Y, Garton HJL, Keep RF, Xi G. Delayed Minocycline Treatment Ameliorates Hydrocephalus Development and Choroid Plexus Inflammation in Spontaneously Hypertensive Rats. Int J Mol Sci 2022; 23:ijms23042306. [PMID: 35216420 PMCID: PMC8874790 DOI: 10.3390/ijms23042306] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 02/14/2022] [Accepted: 02/17/2022] [Indexed: 12/15/2022] Open
Abstract
Hydrocephalus is a complicated disorder that affects both adult and pediatric populations. The mechanism of hydrocephalus development, especially when there is no mass lesion present causing an obstructive, is poorly understood. Prior studies have demonstrated that spontaneously hypertensive rats (SHRs) develop hydrocephalus by week 7, which was attenuated with minocycline. The aim of this study was to determine sex differences in hydrocephalus development and to examine the effect of minocycline administration after hydrocephalus onset. Male and female Wistar-Kyoto rats (WKYs) and SHRs underwent magnetic resonance imaging at weeks 7 and 9 to determine ventricular volume. Choroid plexus epiplexus cell activation, cognitive deficits, white matter atrophy, and hippocampal neuronal loss were examined at week 9. In the second phase of the experiment, male SHRs (7 weeks old) were treated with either saline or minocycline (20 mg/kg) for 14 days, and similar radiologic, histologic, and behavior tests were performed. Hydrocephalus was present at week 7 and increased at week 9 in both male and female SHRs, which was associated with greater epiplexus cell activation than WKYs. Male SHRs had greater ventricular volume and epiplexus cell activation compared to female SHRs. Minocycline administration improved cognitive function, white matter atrophy, and hippocampal neuronal cell loss. In conclusion, while both male and female SHRs developed hydrocephalus and epiplexus cell activation by week 9, it was more severe in males. Delayed minocycline treatment alleviated hydrocephalus, epiplexus macrophage activation, brain pathology, and cognitive impairment in male SHRs.
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Affiliation(s)
| | | | | | | | | | | | - Guohua Xi
- Correspondence: ; Tel.: +1-734-764-1207; Fax: +1-734-763-7322
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Stoyell-Conti FF, Chabbra A, Puthentharayil J, Rigatto K, Speth RC. Chronic administration of pharmacological doses of angiotensin 1-7 and iodoangiotensin 1-7 has minimal effects on blood pressure, heart rate, and cognitive function of spontaneously hypertensive rats. Physiol Rep 2021; 9:e14812. [PMID: 33904655 PMCID: PMC8077095 DOI: 10.14814/phy2.14812] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 12/26/2022] Open
Abstract
Cardiovascular diseases are the principal cause of death worldwide, with hypertension being the most common cardiovascular disease risk factor. High blood pressure (BP) is also associated with an increased risk of poor cognitive performance and dementia including Alzheimer's disease. Angiotensin 1–7 (Ang 1‐7), a product of the renin‐angiotensin system (RAS), exhibits central and peripheral actions to reduce BP. Recent data from our lab reveals that the addition of a non‐radioactive iodine molecule to the tyrosine in position 4 of Ang 1‐7 (iodoAng 1‐7) makes it ~1000‐fold more potent than Ang 1‐7 in competing for the 125I‐Ang 1‐7 binding site (Stoyell‐Conti et al., 2020). Moreover, the addition of the non‐radioactive iodine molecule increases (~4‐fold) iodoAng 1‐7’s ability to bind to the AT1 receptor (AT1R), the primary receptor for Ang II. Preliminary data indicates that iodoAng 1‐7 can also compete for the 125I‐Ang IV binding site with a low micromolar IC50. Thus, our aims were to compare the effects of chronic treatment of the Spontaneously Hypertensive Rat (SHR) with iodoAng 1‐7 (non‐radioactive iodine isotope) and Ang 1‐7 on arterial pressure, heart rate, and cognitive function. For this study, male SHRs were divided into three groups and treated with Saline, Ang 1‐7, or iodoAng 1‐7 administrated subcutaneously using a 28‐day osmotic mini pump. Systolic BP was measured non‐invasively by the tail‐cuff technique. Cognitive function was assessed by Y‐Maze test and novel object recognition (NOR) test. We have demonstrated in SHRs that subcutaneous administration of high doses of iodoAng 1‐7 prevented the increase in heart rate with age, while Ang 1‐7 showed a trend toward preventing the increase in heart rate, possibly by improving baroreflex control of the heart. Conversely, neither Ang 1‐7 nor iodoAng 1‐7 administered subcutaneously affected BP nor cognitive function.
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Affiliation(s)
- Filipe F Stoyell-Conti
- College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL, USA.,Surgery Department, University of Miami, Miami, FL, USA
| | - Alesa Chabbra
- Halmos College of Natural Science & Oceanography, Nova Southeastern University, Fort Lauderdale, FL, USA
| | - Joseph Puthentharayil
- Halmos College of Natural Science & Oceanography, Nova Southeastern University, Fort Lauderdale, FL, USA
| | - Katya Rigatto
- Institute for Neuro-Immune Medicine, Nova Southeastern University, Fort Lauderdale, FL, USA.,Laboratório de Fisiologia Translacional, Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre, RS, Brazil
| | - Robert C Speth
- College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL, USA.,Department of Pharmacology and Physiology, College of Medicine, Georgetown University, Washington, DC, USA
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Activation of the G Protein-Coupled Estrogen Receptor (GPER) Increases Neurogenesis and Ameliorates Neuroinflammation in the Hippocampus of Male Spontaneously Hypertensive Rats. Cell Mol Neurobiol 2019; 40:711-723. [DOI: 10.1007/s10571-019-00766-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 11/22/2019] [Indexed: 01/20/2023]
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Physical exercise prevents memory impairment in an animal model of hypertension through modulation of CD39 and CD73 activities and A2A receptor expression. J Hypertens 2019; 37:135-143. [DOI: 10.1097/hjh.0000000000001845] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Aparicio CF, Hennigan PJ, Mulligan LJ, Alonso-Alvarez B. Spontaneously hypertensive (SHR) rats choose more impulsively than Wistar-Kyoto (WKY) rats on a delay discounting task. Behav Brain Res 2017; 364:480-493. [PMID: 28963043 DOI: 10.1016/j.bbr.2017.09.040] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 09/19/2017] [Accepted: 09/25/2017] [Indexed: 11/29/2022]
Abstract
Indications of Attention Deficit Hyperactivity Disorder (ADHD) in the spontaneously hypertensive rat (SHR) are not consistent across different tests of impulsivity, questioning the SHR's validity as a rodent model of ADHD. This study used a concurrent-chains procedure to examine possible differences in impulsive choice between SHRs and control-normotensive Wistar Kyoto (WKY) rats. The aim was to extend the generality of findings showing regularities between the hyperbolic-decay model and the generalized matching law fitting delay discounting data from nonhuman animals. The objectives were to: (1) examine differences in impulsive choice between SHRs and WKYs; (2) add evidence suggesting that the SHR is a suitable model of ADHD; (3) demonstrate that concurrent-chains procedures requiring locomotion detect differences in impulsive choice between SHRs and WKYs; (4) support the idea that impulsivity in nonhuman animals increases with training. The initial link used two non-independent random interval schedules arranging entries to the terminal links, where one fixed-time (FT) schedule delayed 1-food pellet and the other FT 4-food pellets. The FT delaying the former was kept constant at 0.1s and that delaying the latter changed after every 10 food deliveries, defining six delay components (0.1, 5, 10, 20, 40, and 80s) presented in random order each session. Results showed that the SHRs choose more impulsively than the WKYs, adding to the body of evidence suggesting that the SHR may be a suitable model of ADHD. Both models of choice fitted the impulsive choices of the SHRs and WKYs well; positive correlations between estimates of parameters k and s suggested compatibility between models of choice showing that impulsivity increases with training.
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Phosphodiesterase-4 inhibitors ameliorates cognitive deficits in deoxycorticosterone acetate induced hypertensive rats via cAMP/CREB signaling system. Brain Res 2015; 1622:279-91. [PMID: 26168894 DOI: 10.1016/j.brainres.2015.07.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Revised: 07/02/2015] [Accepted: 07/03/2015] [Indexed: 12/17/2022]
Abstract
Phosphodiesterase-4 (PDE-4) inhibitors promote memory by blocking the degradation of cAMP. Existing evidence also shows that neuronal survival and plasticity are dependent on the phosphorylation of cAMP-response element-binding protein. In this regard, PDE-4 inhibitors have also been shown to reverse pharmacologically and genetically induced memory impairment in animal models. In the present study, the authors examined the effect of both rolipram and roflumilast (PDE-4 inhibitors) on the impairment of learning and memory observed in hypertensive rats. Deoxycorticosterone acetate (DOCA) salt hypertensive model was used to induce learning and memory deficits. The mRNA expression of different PDE-4 subtypes along with the protein levels of pCREB and BDNF in the hippocampus was quantified. Systolic blood pressure was significantly increased in DOCA salt hypertensive rats when compared to sham operated rats. This effect was reversed by clonidine, an α2 receptor agonist, while PDE-4 inhibitors did not. PDE-4 inhibitors significantly improved the time-induced memory deficits in object recognition task (ORT). In DOCA salt hypertensive rats, the gene expression of PDE-4B and PDE-4D was significantly increased. Furthermore, both pCREB and BDNF showed decreased levels of expression in hypertensive rats in comparison to sham operated rats. Repeated administration of PDE-4 inhibitors significantly decreased both PDE-4B and PDE-4D with an increase in the expression of pCREB and BDNF in hypersensitive rats. Also, rolipram, roflumilast and roflumilast N-oxide showed a linear increase in the plasma and brain concentrations after ORT. Our present findings suggested that PDE-4 inhibitors ameliorate hypertension-induced learning impairment via cAMP/CREB signaling that regulates BDNF expression downstream in the rat hippocampus.
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Effects of rolipram and roflumilast, phosphodiesterase-4 inhibitors, on hypertension-induced defects in memory function in rats. Eur J Pharmacol 2015; 746:138-47. [DOI: 10.1016/j.ejphar.2014.10.039] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2014] [Revised: 10/16/2014] [Accepted: 10/18/2014] [Indexed: 12/17/2022]
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López-Gil X, Amat-Roldan I, Tudela R, Castañé A, Prats-Galino A, Planas AM, Farr TD, Soria G. DWI and complex brain network analysis predicts vascular cognitive impairment in spontaneous hypertensive rats undergoing executive function tests. Front Aging Neurosci 2014; 6:167. [PMID: 25100993 PMCID: PMC4107676 DOI: 10.3389/fnagi.2014.00167] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Accepted: 06/30/2014] [Indexed: 01/09/2023] Open
Abstract
The identification of biomarkers of vascular cognitive impairment is urgent for its early diagnosis. The aim of this study was to detect and monitor changes in brain structure and connectivity, and to correlate them with the decline in executive function. We examined the feasibility of early diagnostic magnetic resonance imaging (MRI) to predict cognitive impairment before onset in an animal model of chronic hypertension: Spontaneously Hypertensive Rats. Cognitive performance was tested in an operant conditioning paradigm that evaluated learning, memory, and behavioral flexibility skills. Behavioral tests were coupled with longitudinal diffusion weighted imaging acquired with 126 diffusion gradient directions and 0.3 mm3 isometric resolution at 10, 14, 18, 22, 26, and 40 weeks after birth. Diffusion weighted imaging was analyzed in two different ways, by regional characterization of diffusion tensor imaging (DTI) indices, and by assessing changes in structural brain network organization based on Q-Ball tractography. Already at the first evaluated times, DTI scalar maps revealed significant differences in many regions, suggesting loss of integrity in white and gray matter of spontaneously hypertensive rats when compared to normotensive control rats. In addition, graph theory analysis of the structural brain network demonstrated a significant decrease of hierarchical modularity, global and local efficacy, with predictive value as shown by regional three-fold cross validation study. Moreover, these decreases were significantly correlated with the behavioral performance deficits observed at subsequent time points, suggesting that the diffusion weighted imaging and connectivity studies can unravel neuroimaging alterations even overt signs of cognitive impairment become apparent.
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Affiliation(s)
- Xavier López-Gil
- Experimental 7T MRI Unit, IDIBAPS, Institut d'Investigacions Biomèdiques August Pi i Sunyer Barcelona, Spain
| | | | - Raúl Tudela
- Experimental 7T MRI Unit, IDIBAPS, Institut d'Investigacions Biomèdiques August Pi i Sunyer Barcelona, Spain ; Group of Biomedical Imaging of the University of Barcelona, CIBER de Bioingenieria, Biomateriales y Nanomedicina Barcelona, Spain
| | - Anna Castañé
- Department of Neurochemistry and Neuropharmacology, Institut d'Investigacions Biomèdiques de Barcelona (IIBB-CSIC) Barcelona, Spain ; Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM), ISCIII Madrid, Spain
| | - Alberto Prats-Galino
- Human Anatomy and Embryology Unit, Laboratory of Surgical NeuroAnatomy, Facultat de Medicina, Universitat de Barcelona Barcelona, Spain
| | - Anna M Planas
- Department of Brain Ischemia and Neurodegeneration, Institut d'Investigacions Biomèdiques de Barcelona (IIBB-CSIC) Barcelona, Spain
| | - Tracy D Farr
- Department of Experimental Neurology, Center for Stroke Research Berlin Charité, Berlin, Germany
| | - Guadalupe Soria
- Experimental 7T MRI Unit, IDIBAPS, Institut d'Investigacions Biomèdiques August Pi i Sunyer Barcelona, Spain ; Group of Biomedical Imaging of the University of Barcelona, CIBER de Bioingenieria, Biomateriales y Nanomedicina Barcelona, Spain
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Abstract
The spontaneously hypertensive rat (SHR) is an established animal model of ADHD. It has been suggested that ADHD symptoms arise from deficits in executive functions such as working memory, attentional control and decision making. Both ADHD patients and SHRs show deficits in spatial working memory. However, the data on spatial working memory deficits in SHRs are not consistent. It has been suggested that the reported cognitive deficits of SHRs may be related to the SHRs’ locomotor activity. We have used a holeboard (COGITAT) to study both cognition and activity in order to evaluate the influence of the activity on the cognitive performance of SHRs. In comparison to Wistar-Kyoto (WKY) rats, SHRs did not have any impairment in spatial working memory and reference memory. When the rats’ locomotor activity was taken into account, the SHRs’ working memory and reference memory were significantly better than in WKY rats. The locomotor activity appears to be a confounding factor in spatial memory tasks and should therefore be controlled for in future studies. In the SHR model of ADHD, we were unable to demonstrate an impairment of working memory which has been reported in patients with ADHD.
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Tayebati SK, Tomassoni D, Amenta F. Spontaneously hypertensive rat as a model of vascular brain disorder: microanatomy, neurochemistry and behavior. J Neurol Sci 2012; 322:241-9. [PMID: 22726353 DOI: 10.1016/j.jns.2012.05.047] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 05/23/2012] [Indexed: 11/28/2022]
Abstract
Arterial hypertension is the main risk factor for stroke and plays a role in the development of vascular cognitive impairment (VCI) and vascular dementia (VaD). An association between hypertension and reduced cerebral blood flow and VCI is documented and arterial hypertension in midlife is associated with a higher probability of cognitive impairment. These findings suggest that arterial hypertension is a main cause of vascular brain disorder (VBD). Spontaneously hypertensive rat (SHR) is the rat strain most extensively investigated and used for assessing hypertensive brain damage and treatment of it. They are normotensive at birth and at 6months they have a sustained hypertension. Time-dependent rise of arterial blood pressure, the occurrence of brain atrophy, loss of nerve cells and glial reaction are phenomena shared to some extent with hypertensive brain damage in humans. SHR present changes of some neurotransmitter systems that may have functional and behavioral relevance. An impaired cholinergic neurotransmission characterizes SHR, similarly as reported in patients affected by VaD. SHR are also characterized by a dopaminergic hypofunction and noradrenergic hyperactivity similarly as occurs in attention-deficit with hyperactivity disorder (ADHD). Microanatomical, neurochemical and behavioral data on SHR are in favor of the hypothesis that this strain is a suitable model of VBD. Changes in catecholaminergic transmission put forward SHR as a possible model of ADHD as well. Hence SHR could represent a multi-faced model of two important groups of pathologies, VBD and ADHD. As for most models, researchers should always consider that SHR offer some similarities with corresponding human pathologies, but they do not suffer from the same disease. This paper reviews the main microanatomical, neurochemical and behavioral characteristics of SHR with particular reference as an animal model of brain vascular injury.
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Affiliation(s)
- Seyed Khosrow Tayebati
- School of Medicinal Sciences and Health Products, University of Camerino, Camerino, Italy.
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Meneses A, Perez-Garcia G, Ponce-Lopez T, Tellez R, Gallegos-Cari A, Castillo C. Spontaneously hypertensive rat (SHR) as an animal model for ADHD: a short overview. Rev Neurosci 2011; 22:365-71. [DOI: 10.1515/rns.2011.024] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Age-series characteristics of locomotor activities in spontaneously hypertensive rats: A comparison with the Wistar–Kyoto strain. Physiol Behav 2008; 93:777-82. [DOI: 10.1016/j.physbeh.2007.11.032] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 11/09/2007] [Accepted: 11/21/2007] [Indexed: 11/16/2022]
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Tomassoni D, Avola R, Mignini F, Parnetti L, Amenta F. Effect of treatment with choline alphoscerate on hippocampus microanatomy and glial reaction in spontaneously hypertensive rats. Brain Res 2006; 1120:183-90. [PMID: 16989788 DOI: 10.1016/j.brainres.2006.08.068] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 08/17/2006] [Accepted: 08/18/2006] [Indexed: 10/24/2022]
Abstract
The influence of long term treatment with choline alphoscerate on microanatomy of hippocampus and glial reaction was assessed in spontaneously hypertensive rats (SHR) used as an animal model of cerebrovascular disease. Choline alphoscerate is a cholinergic precursor, which has shown to be effective in countering cognitive symptoms in forms of dementia disorders of degenerative, vascular or combined origin. Male spontaneously hypertensive rats (SHR) aged 6 months and age-matched normotensive Wistar-Kyoto (WKY) rats were treated for 8 weeks with an oral daily dose of 100 mg/kg of choline alphoscerate, 285 mg/kg of phosphatidylcholine (lecithin) or vehicle. On the hippocampus of different animal groups, nerve cell number and GFAP-immunoreactive astrocytes were assessed by neuroanatomical, immunochemical and immunohistochemical techniques associated with quantitative analysis. Treatment with choline alphoscerate countered nerve cell loss and glial reaction primarily in the CA1 subfields and in the dentate gyrus of the hippocampus of SHR. Phosphatidylcholine did not affect hypertension-dependent changes in hippocampal microanatomy. Both compounds did not affect blood pressure values in SHR. These data suggest that choline alphoscerate may play a role in the countering hippocampal changes induced by cerebrovascular involvement. The observation that treatment with choline alphoscerate attenuates the extent of glial reaction in the hippocampus of SHR suggests also that the compound may afford neuroprotection in this animal model of vascular brain damage.
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Affiliation(s)
- Daniele Tomassoni
- Sezione di Anatomia Umana, Dipartimento di Medicina Sperimentale e Sanità Pubblica,Università di Camerino, Camerino, Italy
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Tayebati SK. Animal models of cognitive dysfunction. Mech Ageing Dev 2006; 127:100-8. [PMID: 16293295 DOI: 10.1016/j.mad.2005.09.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2004] [Revised: 02/04/2005] [Accepted: 09/15/2005] [Indexed: 10/25/2022]
Abstract
The increased life expectancy in industrialised countries in the last half century has also brought to a greater incidence of neurological disorders, including neurodegenerative diseases and developing in a rather long time. In this respect, Alzheimer's disease (AD), for the large incidence, and the dramatic loss of autonomy caused by its cognitive and behavioural symptoms represents one of the main challenges of modern medicine. Although AD is a typical human disease and probably includes several nosographic entities, the use of animal models may contribute to understand specific aspects of pathophysiology of the disease. The most widely used animal models are rodents and non-human primates. In this review different animal models characterised by impaired cognitive functions are analysed. None of the models available mimics exactly cognitive, behavioural, biochemical and histopathological abnormalities observed in neurological disorders characterised by cognitive impairment. However, partial reproduction of neuropathology and/or cognitive deficits of Alzheimer's disease (AD), vascular dementia and dementia occurring in Huntington's and Parkinson's diseases, or in other neurodegenerative disorders may represent a basis for understanding pathophysiological traits of these diseases and for contributing to their treatments.
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Affiliation(s)
- Seyed Khosrow Tayebati
- Anatomia Umana, Dipartimento di Medicina Sperimentale e Sanità Pubblica Università di Camerino, 62032 Camerino, Italy.
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Bilkei-Gorzo A, Racz I, Valverde O, Otto M, Michel K, Sastre M, Sarstre M, Zimmer A. Early age-related cognitive impairment in mice lacking cannabinoid CB1 receptors. Proc Natl Acad Sci U S A 2005; 102:15670-5. [PMID: 16221768 PMCID: PMC1266095 DOI: 10.1073/pnas.0504640102] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The molecular mechanisms contributing to the normal age-related decline of cognitive functions or to pathological learning and memory impairment are largely unknown. We demonstrate here that young mice (6-7 weeks) with a genetic deletion of the cannabinoid CB1 receptor performed as well as WT mice, or often better, in a number of learning and memory paradigms, including animal models of skill-learning, partner recognition, and operant conditioning. In contrast, the performance of mature mice (3-5 months) lacking CB1 receptors was much worse than that of age-matched WT animals. In most tests, these mice performed at the same level as old animals (14-17 months), suggesting that the decline in cognitive functions is accelerated in the absence of CB1 receptors. This rapid decline in CB1-deficient animals is accompanied by a loss of neurons in the CA1 and CA3 regions of the hippocampus.
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Affiliation(s)
- A Bilkei-Gorzo
- Laboratory of Molecular Neurobiology, Department of Psychiatry, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany
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Calzavara MB, Lopez GB, Abílio VC, Silva RH, Frussa-Filho R. Role of anxiety levels in memory performance of spontaneously hypertensive rats. Behav Pharmacol 2005; 15:545-53. [PMID: 15577453 DOI: 10.1097/00008877-200412000-00003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Spontaneously hypertensive rats (SHR) show behavioural differences when compared to their strain-matched controls. These differences include decreased anxiety-like behaviour in SHR, while both improved performance and behavioural deficits have been reported in learning/memory studies. Considering that alterations in anxiety levels during the training session can modify retention performance in animal models of memory, the aim of the present study was to investigate the role of anxiety levels in the performance of SHR rats in the plus-maze discriminative avoidance task (PM-DAT), in which memory and anxiety are evaluated simultaneously. Adult (5-month-old) and young (45-day-old) SHR and normotensive Wistar rats (NWR) were treated with chlordiazepoxide (CDZ) or saline. Thirty minutes later, rats were submitted to the PM-DAT training session. After 24 h, the test session was performed. The results showed that: (1) adult SHR showed lower anxiety levels compared to adult NWR; (2) adult SHR and NWR, as well as young NWR, showed significant retention of the task, while young SHR showed impaired performance; (3) 5.0 mg/kg CDZ decreased anxiety levels in adult NWR and young and adult SHR; (4) 5.0 mg/kg CDZ impaired retention in adult SHR and NWR and increased retention in young SHR. Our data suggest an important role of anxiety levels in the performance of SHR in a plus-maze discriminative avoidance task.
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Affiliation(s)
- M B Calzavara
- Department of Pharmacology, Universidade Federal de São Paulo, São Paulo, Brazil
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Braszko JJ, Karwowska-Polecka W, Halicka D, Gard PR. Captopril and enalapril improve cognition and depressed mood in hypertensive patients. J Basic Clin Physiol Pharmacol 2005; 14:323-43. [PMID: 15198305 DOI: 10.1515/jbcpp.2003.14.4.323] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
UNLABELLED In this study, we evaluate the effects of two angiotensin converting enzyme inhibitors (ACEIs), captopril and enalapril given chronically as antihypertensive treatment, on certain cognitive and emotional processes in humans. Thirty-nine subjects with mild to moderate hypertension and fifteen normotensive controls were divided into four groups consisting of normotensive and hypertensive subjects taking captopril, enalapril, or no medication at all. The Rey Auditory Verbal Learning Test and the Wechsler Memory Scale were used to evaluate their cognitive functioning. Mood changes in all subjects were assessed using the Beck Depression Inventory and the Hopkins Symptom Check- list (HSC). RESULTS Untreated hypertensive patients scored lower than normotensive controls in cognitive tests and significantly worse in cumulative recall (P < 0.05) and paired words association (P < 0.01). When compared with normotensive subjects, untreated hypertensive patients also scored significantly higher on the depression with anxiety subscale in HSC (P < 0.05). No significant influence of hypertension was found in any other examined aspect of cognition and mood. In most cases captopril improved and enalapril reversed the adverse memory effects of hypertension. High arterial blood pressure is significantly associated with an impairment of cognition and the occurrence of depression with anxiety in humans. Enalapril and, to a lesser extent, captopril reversed these deficits.
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Affiliation(s)
- Jan J Braszko
- Department of Clinical Pharmacology, Medical University of Bialystok, Sklodowskiej 24a, 15276 Bialystok, Poland.
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Mignini F, Vitaioli L, Sabbatini M, Tomassoni D, Amenta F. The cerebral cortex of spontaneously hypertensive rats: a quantitative microanatomical study. Clin Exp Hypertens 2004; 26:287-303. [PMID: 15195685 DOI: 10.1081/ceh-120034135] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The morphology of cerebral cortex was investigated in male spontaneously hypertensive rats (SHR) aged 2, 4 and 6 months (pre-hypertensive, developing hypertension and established hypertension respectively) and in age-matched normotensive Wistar-Kyoto (WKY) rats using quantitative microanatomical techniques. Analysis included frontal and occipital cortex as a paradigm of motor and sensory cerebrocortical areas respectively. Values of systolic pressure were slightly higher in 2-month-old SHR compared to age-matched WKY rats and augmented progressively with increasing age in SHR. In frontal cortex of SHR a decrease of nerve cell number and of cortical volume was observed in layers V and VI of 4- and 6- month-old SHR, and in layers I-IV of 6- month-old SHR. In occipital cortex a decrease of the number of nerve cells and of cortical volume was observed in layers V and VI of 2-, 4-, 6- month-old SHR, and in layers I-IV of 6-month-old SHR. Numerical decrease of neurons in SHR affected to a greater extent occipital cortex than frontal cortex. An increase in the number of glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes (hyperplasia) as well as in the mean immune reaction area (hypertrophy) was found in the two cerebrocortical areas investigated of 6-month-old SHR. The occurrence of apoptosis and/or necrosis identified using the terminal deoxyribo-nucleotidyl transferase (TdT)-mediated biotin-16-dUTP nick-end labeling (TUNEL) technique was also observed in frontal and occipital cortex of 6-month-old SHR, but not of younger cohorts. These findings indicate the development of microanatomical changes in the cerebral cortex of SHR, the extent of which increases parallel with the progression of hypertension. The occurrence of cerebrocortical apoptosis and/or necrosis as well as the obvious astrogliosis occurring in established hypertension may account for the increased risk of vascular dementia that represents a specific trait of complicated hypertension.
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Affiliation(s)
- Fiorenzo Mignini
- Sezione di Anatomia Umana, Dipartimento di Scienze Farmacologiche e Medicina Sperimentale, Università di Camerino, Camerino, Italy
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Mulder M, Jansen PJ, Janssen BJA, van de Berg WDJ, van der Boom H, Havekes LM, de Kloet RE, Ramaekers FCS, Blokland A. Low-density lipoprotein receptor-knockout mice display impaired spatial memory associated with a decreased synaptic density in the hippocampus. Neurobiol Dis 2004; 16:212-9. [PMID: 15207278 DOI: 10.1016/j.nbd.2004.01.015] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2003] [Revised: 01/16/2004] [Accepted: 01/20/2004] [Indexed: 11/20/2022] Open
Abstract
The low-density lipoprotein receptor (LDLR) is the first described receptor for apolipoprotein E (apoE). We hypothesize that the absence of the LDLR, similar to the absence of apoE, results in impaired learning and memory processes. Six-month-old homozygous Ldlr-/- and wild-type littermates (Ldlr+/+), maintained on a standard lab chow diet, were used. Unlike humans, Ldlr-/- mice, under these conditions, do not develop atherosclerosis. The results of the Morris water escape task revealed an impaired spatial memory in the Ldlr-/- mice in comparison with Ldlr+/+ mice. Also in a T-maze task, the working memory performance of the Ldlr-/- mice was impaired. Furthermore, Ldlr-/- mice, in comparison with Ldlr+/+ mice, display a decreased number of synaptophysin-immunoreactive presynaptic boutons in the hippocampus CA1. In conclusion, the results show in mice deficiency for the LDLR results in impaired hippocampal-dependent memory functions. A decrease in the number of presynaptic boutons may underlay these behavioral alterations. Therefore, the LDLR may be an important receptor for apoE in the central nervous system.
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Affiliation(s)
- Monique Mulder
- Department of Molecular Cell Biology, Maastricht University and University Hospital Maastricht, Maastricht, The Netherlands.
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Amenta F, Tomassoni D. Treatment with Nicardipine Protects Brain in an Animal Model of Hypertension‐Induced Damage. Clin Exp Hypertens 2004; 26:351-61. [PMID: 15195689 DOI: 10.1081/ceh-120034139] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Control of blood pressure protects from the development of cerebrovascular lesions and vascular dementia (VaD). This study has assessed the influence of treatment with the dihydropyridine-type Ca2+ antagonist nicardipine on brain microanatomical changes in spontaneously hypertensive rats (SHR). SHR were treated from 16th to 26th week of age with hypotensive (3 mg/Kg/day) or non-hypotensive (0.1 mg/Kg/day) doses of nicardipine, with the non-dihydropyridine-type vasodilator hydralazine (10 mg/kg/day) or with vehicle (control group). Untreated age-matched Wistar Kyoto (WKY) rats were used as a normotensive reference group. Brain volume, number of neurons, glial fibrillary-acidic protein (GFAP)-immunoreactive astrocytes and neurofilament 200 KDa (NFP)-immunoreactivity (IR) were assessed in frontal and occipital cortex, hippocampus and striatum. A decrease of volume and number of nerve cells and a loss of NFP-IR was found in the frontal and occipital cortex and in the CA1 subfield of hippocampus and in the striatum of SHR. Treatment with nicardipine countered microanatomical changes occurring in SHR, whereas hydralazine displayed a less pronounced effect. Comparatively, the non-hypotensive dose of nicardipine was less active than the hypotensive one. The observation that equihypotensive doses of nicardipine or hydralazine did not protect brain in the same way from hypertensive brain damage suggests that lowering blood pressure is per se not enough for affording neuroprotection. The demonstration of neuroprotective effect of nicardipine suggests an use of the compound in situations in which hypertension is accompanied by the risk of brain damage.
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Affiliation(s)
- Francesco Amenta
- Sezione di Anatomia Umana, Dipartimento di Scienze Farmacologiche e Medicina Sperimentale, Università di Camerino, Camerino, Italy.
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Amenta F, Di Tullio MA, Tomassoni D. Arterial hypertension and brain damage--evidence from animal models (review). Clin Exp Hypertens 2003; 25:359-80. [PMID: 12940473 DOI: 10.1081/ceh-120023545] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Hypertension is an important risk factor for cerebrovascular disease including stroke and has also a role in the development of vascular cognitive impairment (VCI) and vascular dementia (VaD). Research on pathophysiology and treatment of hypertensive brain damage may benefit from the availability of animal models. This paper has reviewed the main animal models of hypertension in which brain damage is documented. Spontaneously hypertensive rats (SHR) represent the animal model more largely used. In these rats cerebrovascular changes, brain atrophy, loss of nerve cells in cerebrocortical areas, and glial reaction were documented. Several changes observed in SHR are similar to those found by in vivo imaging studies in essential hypertensives. It is documented that brain gets benefit from lowering abnormally elevated blood pressure and that reduction of hypertension protects brain from stroke and probably reduces the incidence of VaD. The influence of anti-hypertensive treatment on brain structure and function in animal models of hypertension is reviewed. Among classes of drugs investigated, dihydropyridine-type Ca2+ antagonists were those with a most documented protective effect on hypertensive brain damage. Limits and perspectives in the use of animal models for assessing brain damage caused by hypertension and protection from it are discussed.
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Affiliation(s)
- Francesco Amenta
- Sezione di Anatomia Umana, Dipartimento di Scienze Farmacologiche e Medicina Sperimentale, Università di Camerino, Camerino, Italy.
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De Bruin NMWJ, Kiliaan AJ, De Wilde MC, Broersen LM. Combined uridine and choline administration improves cognitive deficits in spontaneously hypertensive rats. Neurobiol Learn Mem 2003; 80:63-79. [PMID: 12737935 DOI: 10.1016/s1074-7427(03)00024-8] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Rationale. Hypertension is considered a risk factor for the development of cognitive disorders, because of its negative effects on cerebral vasculature and blood flow. Genetically induced hypertension in rats has been associated with a range of cognitive impairments. Therefore, spontaneously hypertensive rats (SHR) can potentially be used as a model for cognitive deficits in human subjects. Consecutively, it can be determined whether certain food components can improve cognition in these rats. Objective. The present study aimed to determine whether SHR display specific deficits in attention, learning, and memory function. Additionally, effects of chronic uridine and choline administration were studied. Methods. 5-7 months old SHR were compared with normotensive Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats. (a) The operant delayed non-matching-to-position (DNMTP) test was used to study short-term memory function. (b) The five-choice serial reaction time (5-CSRT) task was used to assess selective visual attention processes. (c) Finally, the Morris water maze (MWM) acquisition was used as a measure for spatial learning and mnemonic capabilities. Results. (1) SHR exhibited significantly impaired performance in the 5-CSRT test in comparison with the two other rat strains. Both the SHR and WKY showed deficits in spatial learning when compared with the SD rats. (2) Uridine and choline supplementation normalized performance of SHR in the 5-CSRT test. (3) In addition, uridine and choline treatment improved MWM acquisition in both WKY and SHR rats. Conclusion. The present results show that the SHR have a deficiency in visual selective attention and spatial learning. Therefore, the SHR may provide an interesting model in the screening of substances with therapeutic potential for treatment of cognitive disorders. A combination of uridine and choline administration improved selective attention and spatial learning in SHR.
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Affiliation(s)
- N M W J De Bruin
- Numico Research B.V., Department of Condition and Disease Specific Research/Neuroendocrinology section, Bosrandweg 20, 6704 PH Wageningen, PO Box 7005, 6700 CA Wageningen, The Netherlands.
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Abstract
According to current diagnostic criteria, a definite diagnosis of vascular dementia (VaD) can be reached on pathological grounds by showing the presence of vascular lesions and the absence of degenerative changes exceeding those expected for age. However, while it is commonly accepted that VaD is a group of heterogeneous entities rather than a process with a unique pathological substrate, the spectrum of vessel and parenchyma changes etiologically associated with the clinical syndrome remains basically unidentified. The review of some recent clinical-pathological series shows that different studies have assessed the presence of dissimilar vascular lesions and that, in many cases, no pathological definition was given. This has hindered the clarification of clinical-pathological correlations in the field of VaD. In this scenario, the use of animal models of cerebrovascular diseases may help to elucidate the type of lesions possibly linked with cognitive impairment in humans and might provide insight into some of the pathophysiological mechanisms of vascular cognitive impairment. A consensus is today needed in order to harmonize the pathological examination of vascular lesions in cases of dementia. An ongoing survey aimed at collecting information about the procedures used in different pathological laboratories in the assessment of lesions possibly associated with dementia is finally presented.
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Affiliation(s)
- Leonardo Pantoni
- Department of Neurological and Psychiatric Sciences, University of Florence, Viale Morgagni 85, 50134 Florence, Italy.
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Amenta F, Di Tullio MA, Tomassoni D. The cholinergic approach for the treatment of vascular dementia: evidence from pre-clinical and clinical studies. Clin Exp Hypertens 2002; 24:697-713. [PMID: 12450245 DOI: 10.1081/ceh-120015346] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The involvement of an impaired cholinergic neurotransmission in the pathophysiology of cognitive impairment occurring in vascular dementia (VaD), as well as the possibility of treating it by stimulating cholinergic neurotransmission was reviewed. Pre-clinical data suggest that similarly as documented in dementia disorders of neurodegenerative origin, a cholinergic deficit is involved in the pathophysiology of cognitive impairment of vascular origin. In the past, clinical trials have evaluated cholinergic precursors such as lecithin, citicoline and choline alphoscerate. More recent investigations have assessed acetylcholinesterase (AChE) and cholinesterase (ChE) inhibitors such as donepezil, rivastigmine and galantamine. In general, treatment with citicoline, choline alphoscerate, as well as with AChE and ChE inhibitors induced favourable effects on cognitive function in dementia disorders of vascular origin. These positive results should be regarded with caution due to the small number of patients included in controlled clinical trials using cholinergic precursors and to the limited number and sample size of trials with AChE and ChE inhibitors. Among compounds investigated, choline alphoscerate was well tolerated, improved cognitive function in VaD patients to a better extent than citicoline and to similar or better extent than other more recently developed drugs. This particular profile would justify reconsideration of the compound in larger controlled clinical trials for the treatment of cognitive dysfunction associated with dementia disorders of vascular origin.
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Affiliation(s)
- Francesco Amenta
- Clinical Research Unit, Department of Pharmacological Sciences and Experimental Medicine, University of Camerino, 62032 Camerino, Italy.
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Meneses A, Hong E. Spontaneously hypertensive rats: a potential model to identify drugs for treatment of learning disorders. Hypertension 1998; 31:968-72. [PMID: 9535422 DOI: 10.1161/01.hyp.31.4.968] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Spontaneously hypertensive rats (SHR) of 3 to 12 months of age learned and retrieved less information than normotensive Wistar-Kyoto rats (WKY), although no difference was found with animals from 18 and 24 months of age. The combined influence of hypertension and aging had an additive detrimental effect on cognitive functions. Notwithstanding these deficiencies in learning and memory, SHR have seldom been used as a model in the screening of drugs with therapeutic potential for treatment of disorders of cognitive processes. Moreover, the calcium channel blocker nimodipine has beneficial effects on learning in both aged and hypertensive animals and humans. However, no attempt has been made to investigate whether nimodipine can reverse the additive deleterious effects of aging and hypertension in the same subject. We recently reported that deteriorated animals (middle-aged and/or hypertensive) chronically treated with nimodipine (via osmotic minipumps) exhibit higher learning scores. This information indicates that nimodipine can reverse the impairing effects of either aging or hypertension on learning; the presence of the two conditions, however, produces a severe impairment that can be partially reversed by this drug. Therefore, we propose that mature and middle-aged SHR represent a model for the screening of potentially useful drugs in the treatment of learning disorders, probably associated with hypertension and/or aging. Nevertheless, it must be remembered that the SHR is a genetic model and the appearance of neural disturbances could be a parallel genetic phenomenon and not necessarily or exclusively related to hypertension per se.
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Affiliation(s)
- A Meneses
- Departamento de Farmacología y Toxicología, CINVESTAV-IPN, Tepepan, México City
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Abstract
The effects of post-training (i.p.) injection of TFMPP, mCPP, DOI or 1-NP in the autoshaping learning task was explored. Furthermore, the post-training effects of these agonists after treatment with the antagonists (+/-)-pindolol, (+/-)-propranolol, NAN-190, ketanserin, ritanserin, mesulergine, MDL-72222 or p-chloroamphetamine (5-HT depleter) were studied. Rats were individually trained with a lever-press response (conditioned response; CR) on the autoshaping task and tested 24 h later. The results showed that the injection of TFMPP (1-10 mg/kg), mCPP (1-10 mg/kg), 1-NP (0.1-1.0 mg/kg) or mesulergine (0.4 mg/kg) decreased the rate of CR, while DOI (0.01-0.1 mg/kg) and ritanserin (0.5 mg/kg) and ketanserin (0.001-0.1 mg/kg) increased it. However, the effect induced by TFMPP was reversed by (+/-)-pindolol, ketanserin, ritanserin and PCA; the mCPP-induced effect was antagonized by (+/-)-propranolol, ketanserin, ritanserin and MDL-72222; and the effect produced by 1-NP was reversed by ketanserin, ritanserin and PCA. In addition, the increment in CR provoked by DOI was enhanced by ketanserin, and reversed by ritanserin, mesulergine and PCA. These findings suggest that TFMPP, 1-NP and DOI exerted their effects via stimulation of presynaptic 5-HT receptors. The effects of mCPP most probably reflect activation of postsynaptic receptors. The present data suggest that both 5-HT1B and 5-HT2A-2C receptors play a significant role in the consolidation of learning.
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Affiliation(s)
- A Meneses
- Depto. de Farmacología y Toxicología, CINVESTAV-IPN, México D.F., México
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