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Kundu P, Neese SL, Bandara S, Monaikul S, Helferich WG, Doerge DR, Khan IA, Schantz SL. The effects of the botanical estrogen, isoliquiritigenin on delayed spatial alternation. Neurotoxicol Teratol 2018; 66:55-62. [PMID: 29408209 PMCID: PMC5856646 DOI: 10.1016/j.ntt.2018.02.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 12/18/2017] [Accepted: 02/01/2018] [Indexed: 10/18/2022]
Abstract
Age-related declines in cognitive function can impair working memory, reduce speed of processing, and alter attentional resources. In particular, menopausal women may show an acceleration in the rate of cognitive decline as well as an increased vulnerability to brain diseases as estrogens may play a neuroprotective and neurotrophic role in the brain. To treat menopausal symptoms, many women turn to botanical estrogens that are promoted as a safe and natural alternative to traditional hormone replacement therapy. However, the majority of these compounds have not been systematically evaluated for efficacy and safety. The current study investigated the efficacy of the commercially available botanical estrogenic compound isoliquiritigenin (ISL) to alter performance on an operant working memory task, delayed spatial alternation (DSA). ISL is a compound found in licorice root that has been shown to have a wide range of effects on different biological systems, including estrogenic properties. This botanical is currently being used in over the counter dietary supplements. Middle-aged (12-month old) Long-Evans female rats were ovariectomized and orally dosed with either 0 mg, 6 mg, 12 mg or 24 mg of ISL 60 min before testing on the DSA task. The DSA task required the rat to alternate its responses between two retractable levers in order to earn food rewards. Random delays of 0, 3, 6, 9 or 18 s were imposed between opportunities to press. ISL treatment failed to alter DSA performance. Previous work from our research group has found that estrogenic compounds, including 17β-estradiol and the botanical estrogen genistein impair performance on the DSA task. The goal of our botanical estrogens research is to find compounds that offer some of the beneficial effects of estrogen supplementation, without the harmful effects. This work suggests that ISL may not carry the cognitive risks associated with most other estrogenic compounds tested to date.
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Affiliation(s)
- Payel Kundu
- University of Illinois at Urbana-Champaign, Beckman Institute, 405 N Mathews Ave, Urbana, IL 61801, USA; University of Illinois at Urbana-Champaign, Neuroscience Program, USA.
| | - Steven L Neese
- University of Illinois at Urbana-Champaign, Beckman Institute, 405 N Mathews Ave, Urbana, IL 61801, USA.
| | - Suren Bandara
- University of Illinois at Urbana-Champaign, Beckman Institute, 405 N Mathews Ave, Urbana, IL 61801, USA.
| | - Supida Monaikul
- University of Illinois at Urbana-Champaign, Beckman Institute, 405 N Mathews Ave, Urbana, IL 61801, USA.
| | - William G Helferich
- University of Illinois at Urbana-Champaign, Department of Food Science and Human Nutrition, 905 S. Goodwin, Urbana, IL 61801, USA.
| | - Daniel R Doerge
- National Center for Toxicological Research, U.S. Food & Drug Administration, 3900 NCTR Road, Jefferson, AR 72079, USA.
| | - Ikhlas A Khan
- The University of Mississippi, 1558 University Circle, P.O. Box 1848, University, MS 38677, USA.
| | - Susan L Schantz
- University of Illinois at Urbana-Champaign, Beckman Institute, 405 N Mathews Ave, Urbana, IL 61801, USA; University of Illinois at Urbana-Champaign, Department of Comparative Biosciences, Neuroscience Program, Veterinary Medicine Basic Sciences Bldg. 2001 South Lincoln Avenue Urbana, IL 61802, USA.
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Pisani SL, Neese SL, Katzenellenbogen JA, Schantz SL, Korol DL. Estrogen Receptor-Selective Agonists Modulate Learning in Female Rats in a Dose- and Task-Specific Manner. Endocrinology 2016; 157:292-303. [PMID: 26465198 PMCID: PMC4701887 DOI: 10.1210/en.2015-1616] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Estrogens are well known for their enhancing effects on hippocampus-sensitive cognition. However, estrogens can also impair learning and memory, particularly the acquisition of striatum-sensitive tasks. These cognitive shifts appear to be mediated through local estrogen receptor (ER) activation in each neural structure, but little information is known regarding which specific ER subtypes drive the opposing effects on learning. Elucidating the mnemonic roles of discrete ER subtypes is essential for predicting how treatments with distinct ER pharmacology such as drugs, hormone therapies, and phytoestrogen supplements affect cognitive abilities in and thus the daily lives of the women who take them. The present study examined the effects of the ERα-selective compound propyl pyrazole triol and the ERβ-selective compounds diarylpropionitrile and Br-ERb-041 on place and response learning in young adult female rats. Long-Evans rats were ovariectomized and maintained on phytoestrogen-free chow for 3 weeks before behavioral training, with treatments administered via subcutaneous injection 48 and 24 hours before testing. A dose-response paradigm was used, with each compound tested at 4 different doses in separate groups of rats. Propyl pyrazole triol, diarylpropionitrile, and Br-ERb-041 all enhanced place learning and impaired response learning, albeit with distinct dose-response patterns for each compound and task. These results are consistent with the detection of ERα and ERβ in the hippocampus and striatum and suggest that learning is modulated via activation of either ER subtype.
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Affiliation(s)
- Samantha L Pisani
- Neuroscience Program (S.L.P., S.L.N., S.L.S., D.L.K.) and Department of Chemistry (J.A.K.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Comparative Biosciences (S.L.N., S.L.S.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61802; Department of Psychology and Neuroscience (S.L.N.), Baldwin Wallace University, Berea, Ohio 44017; and Department of Biology (D.L.K.), Syracuse University, Syracuse, New York 13244
| | - Steven L Neese
- Neuroscience Program (S.L.P., S.L.N., S.L.S., D.L.K.) and Department of Chemistry (J.A.K.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Comparative Biosciences (S.L.N., S.L.S.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61802; Department of Psychology and Neuroscience (S.L.N.), Baldwin Wallace University, Berea, Ohio 44017; and Department of Biology (D.L.K.), Syracuse University, Syracuse, New York 13244
| | - John A Katzenellenbogen
- Neuroscience Program (S.L.P., S.L.N., S.L.S., D.L.K.) and Department of Chemistry (J.A.K.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Comparative Biosciences (S.L.N., S.L.S.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61802; Department of Psychology and Neuroscience (S.L.N.), Baldwin Wallace University, Berea, Ohio 44017; and Department of Biology (D.L.K.), Syracuse University, Syracuse, New York 13244
| | - Susan L Schantz
- Neuroscience Program (S.L.P., S.L.N., S.L.S., D.L.K.) and Department of Chemistry (J.A.K.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Comparative Biosciences (S.L.N., S.L.S.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61802; Department of Psychology and Neuroscience (S.L.N.), Baldwin Wallace University, Berea, Ohio 44017; and Department of Biology (D.L.K.), Syracuse University, Syracuse, New York 13244
| | - Donna L Korol
- Neuroscience Program (S.L.P., S.L.N., S.L.S., D.L.K.) and Department of Chemistry (J.A.K.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Comparative Biosciences (S.L.N., S.L.S.), University of Illinois at Urbana-Champaign, Urbana, Illinois 61802; Department of Psychology and Neuroscience (S.L.N.), Baldwin Wallace University, Berea, Ohio 44017; and Department of Biology (D.L.K.), Syracuse University, Syracuse, New York 13244
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Neese SL, Pisani SL, Doerge DR, Helferich WG, Sepehr E, Chittiboyina AG, Rotte SCK, Smillie TJ, Khan IA, Korol DL, Schantz SL. The effects of dietary treatment with S-equol on learning and memory processes in middle-aged ovariectomized rats. Neurotoxicol Teratol 2014; 41:80-8. [PMID: 24368316 PMCID: PMC3943933 DOI: 10.1016/j.ntt.2013.12.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 11/22/2013] [Accepted: 12/17/2013] [Indexed: 01/18/2023]
Abstract
The use of over-the-counter botanical estrogens containing isolated soy isoflavones, including genistein and daidzein, has become a popular alternative to traditional hormone therapies. Menopausal women use these products as an aide in healthy aging, including for the maintenance of cognitive function. The safety and efficacy of many of these commercial preparations remain unknown. Previous research in our lab found that treatment of ovariectomized (OVX) female Long-Evans rats with genistein impaired working memory in an operant delayed spatial alternation (DSA) task and response learning in a plus-maze, but enhanced place learning assessed in the plus-maze. The present study further examined the effects of isolated isoflavones on working memory and place learning by treating middle-aged (12-13 month old) OVX female Long-Evans rats with S-equol, the exclusive enantiomer produced by metabolism of daidzein in the mammalian gut. S-equol binds selectively to ERβ with an affinity similar to that of genistein but has low transcriptional potency. For DSA testing, S-equol at 1.94, 0.97 mg, or 0mg (sucrose control) was orally administered to animals daily, 30 min before behavioral testing, and again both 4 and 8 hours after the first treatment. Rats were tested on the DSA task following the first, morning dose. For place learning, rats received 0.97 mg S-equol every 4 hours during the light portion of the cycle beginning 48 hours prior to behavioral testing (total exposure 8.7 mg S-equol). S-equol treatment was largely without effect on the DSA and place learning tasks. This is the first study to test the behavioral effects of isolated S-equol in OVX rodents, and shows that, unlike genistein or estradiol, repeated daily treatment with this isoflavone metabolite does not alter learning and memory processes in middle-aged OVX rats.
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Affiliation(s)
- Steven L Neese
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, 2001S. Lincoln Avenue, Urbana, IL 61802, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, 505 South Goodwin Avenue, Urbana, IL 61801, USA; Department of Psychology and Neuroscience, Baldwin Wallace University, 275 Eastland Road, Berea, OH 44017, USA.
| | - Samantha L Pisani
- Neuroscience Program, University of Illinois at Urbana-Champaign, 505 South Goodwin Avenue, Urbana, IL 61801, USA.
| | - Daniel R Doerge
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079-9502, USA.
| | - William G Helferich
- Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, 905S Goodwin Avenue, Urbana, IL 61801, USA.
| | - Estatira Sepehr
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration, 3900 NCTR Road, Jefferson, AR 72079-9502, USA.
| | - Amar G Chittiboyina
- National Center for Natural Product Research, University of Mississippi, 3011 Thad Cochran Research Center, University, MS 38677, USA.
| | - Sateesh Chandra Kumar Rotte
- National Center for Natural Product Research, University of Mississippi, 3011 Thad Cochran Research Center, University, MS 38677, USA.
| | - Troy J Smillie
- National Center for Natural Product Research, University of Mississippi, 3011 Thad Cochran Research Center, University, MS 38677, USA.
| | - Ikhlas A Khan
- National Center for Natural Product Research, University of Mississippi, 3011 Thad Cochran Research Center, University, MS 38677, USA.
| | - Donna L Korol
- Neuroscience Program, University of Illinois at Urbana-Champaign, 505 South Goodwin Avenue, Urbana, IL 61801, USA; Department of Biology, Syracuse University, 107 College Place, Syracuse, NY 13244, USA.
| | - Susan L Schantz
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, 2001S. Lincoln Avenue, Urbana, IL 61802, USA; Neuroscience Program, University of Illinois at Urbana-Champaign, 505 South Goodwin Avenue, Urbana, IL 61801, USA.
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Neese SL, Doran M, Clough RW. Evaluation of Degenerating Neurons After Traumatic Brain Injury: Cyromicrotomy and Staining Procedures for Frozen Sections of Rat Brains. J Histotechnol 2013. [DOI: 10.1179/his.2007.30.2.109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Abstract
Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) widely used in common consumer products containing polycarbonate plastics and epoxy resins. Previous studies indicate that other EDCs have species-dependent effects. Furthermore, some EDCs are known to have different effects in different strains within the same species. Little information, however, is known about whether the effects of BPA on the ovary differ by strain. Previous studies have shown that BPA inhibits follicle growth, induces atresia, and inhibits steroidogenesis and expression of steroidogenic enzymes in antral follicles from adult FVB mice. Thus, this study was designed to expand previous work by testing the hypothesis that mouse strain may differentially affect the susceptibility of adult antral follicles to BPA-induced toxicity. To test this hypothesis, antral follicles were mechanically isolated from adult FVB, CD-1, and C57BL/6 mice, individually cultured for 6-120 h and treated with either vehicle control (dimethylsulfoxide) or various concentrations of BPA (1.0 μg/ml, 10 μg/ml, or 100 μg/ml). After culture, media were subjected to measurements of hormone production via ELISA, and follicles were subjected to real-time PCR for analysis of genes known to regulate steroidogenesis, the cell cycle, and atresia. Overall, BPA inhibited follicle growth and steroidogenesis in all tested strains, but CD-1 follicles were slightly more sensitive to BPA at early time points than FVB and C57BL/6 follicles. These data suggest that CD-1, FVB, and C57BL/6 mice can all be used to investigate the effects of BPA on ovarian follicles.
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Affiliation(s)
- Jackye Peretz
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Urbana, Illinois
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Neese SL, Korol DL, Schantz SL. Voluntary exercise impairs initial delayed spatial alternation performance in estradiol treated ovariectomized middle-aged rats. Horm Behav 2013; 64:579-88. [PMID: 24013039 PMCID: PMC3855313 DOI: 10.1016/j.yhbeh.2013.08.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Revised: 07/22/2013] [Accepted: 08/22/2013] [Indexed: 11/21/2022]
Abstract
Estrogens differentially modulate behavior in the adult female rodent. Voluntary exercise can also impact behavior, often reversing age associated decrements in memory processes. Our research group has published a series of papers reporting a deficit in the acquisition of an operant working memory task, delayed spatial alternation (DSA), following 17β-estradiol treatment to middle-aged ovariectomized (OVX) rats. The current study examined if voluntary exercise could attenuate the 17β-estradiol induced deficits on DSA performance. OVX 12-month old Long-Evans rats were implanted with a Silastic capsule containing 17β-estradiol (10% in cholesterol: low physiological range) or with a blank capsule. A subset of the 17β-estradiol and OVX untreated rats were given free access to a running wheel in their home cage. All rats were tested for 40 sessions on the DSA task. Surprisingly, we found running wheel access to impair initial acquisition of the DSA task in 17β-estradiol treated rats, an effect not seen in OVX untreated rats given running wheel access. This deficit was driven by an increase in perseverative responding on a lever no longer associated with reinforcement. We also report for the first time a 17β-estradiol induced impairment on the DSA task following a long intertrial delay (18-sec), an effect revealed following more extended testing than in our previous studies (15 additional sessions). Overall, running wheel access increased initial error rate on the DSA task in 17β-estradiol treated middle-aged OVX rats, and failed to prevent the 17β-estradiol induced deficits in performance of the operant DSA task in later testing sessions.
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Affiliation(s)
- Steven L Neese
- Neuroscience Program, University of Illinois at Urbana-Champaign, USA; Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, USA; Department of Psychology and Neuroscience, Baldwin Wallace University, USA.
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Neese SL, Bandara SB, Schantz SL. Working memory in bisphenol-A treated middle-aged ovariectomized rats. Neurotoxicol Teratol 2013; 35:46-53. [PMID: 23339879 DOI: 10.1016/j.ntt.2013.01.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 12/19/2012] [Accepted: 01/08/2013] [Indexed: 02/02/2023]
Abstract
Over 90% of the U.S. population has detectable bisphenol-A (BPA) in their urine according to recent biomonitoring data. BPA is best known for its estrogenic properties, and most rodent research on the nervous system effects of BPA has focused on determining if chronic exposures during pre- and perinatal development have organizational effects on brain development and behavior. Estrogens also have important impacts on brain and behavior during adulthood, particularly in females during aging, but the impact of BPA on the adult brain is less studied. We have published a series of studies documenting that chronic exposure to various estrogens including 17β-estradiol, ERβ selective SERMs and soy phytoestrogens impairs performance of middle-aged female rats on an operant working memory task. The purpose of this study was to determine if chronic oral exposure to BPA would alter working memory on this same task. Ovariectomized (OVX) middle-aged Long Evans rats were tested on an operant delayed spatial alternation (DSA) task. Rats were treated for 8-10 weeks with either a 0 (vehicle control), 5 or 50 μg/kg bw/day oral bolus of BPA. A subset of the vehicle control rats was implanted with a Silastic implant containing 17β-estradiol (low physiological range) to serve as a positive control. All rats were tested for 25 sessions on the DSA task. BPA treatment did not influence performance accuracy on the DSA task, whereas 17β-estradiol significantly impaired performance, as previously reported. The results of this study suggest that chronic oral exposure to BPA does not alter working memory processes of middle-aged OVX rats assessed by this operant DSA task.
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Affiliation(s)
- Steven L Neese
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, Urbana, IL 61802, United States.
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Pisani SL, Neese SL, Doerge DR, Helferich WG, Schantz SL, Korol DL. Acute genistein treatment mimics the effects of estradiol by enhancing place learning and impairing response learning in young adult female rats. Horm Behav 2012; 62:491-9. [PMID: 22944517 PMCID: PMC3495242 DOI: 10.1016/j.yhbeh.2012.08.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 08/17/2012] [Accepted: 08/20/2012] [Indexed: 12/12/2022]
Abstract
Endogenous estrogens have bidirectional effects on learning and memory, enhancing or impairing cognition depending on many variables, including the task and the memory systems that are engaged. Moderate increases in estradiol enhance hippocampus-sensitive place learning, yet impair response learning that taps dorsal striatal function. This memory modulation likely occurs via activation of estrogen receptors, resulting in altered neural function. Supplements containing estrogenic compounds from plants are widely consumed despite limited information about their effects on brain function, including learning and memory. Phytoestrogens can enter the brain and signal through estrogen receptors to affect cognition. Enhancements in spatial memory and impairments in executive function have been found following treatment with soy phytoestrogens, but no tests of actions on striatum-sensitive tasks have been made to date. The present study compared the effects of acute exposure to the isoflavone genistein with the effects of estradiol on performance in place and response learning tasks. Long-Evans rats were ovariectomized, treated with 17β-estradiol benzoate, genistein-containing sucrose pellets, or vehicle (oil or plain sucrose pellets) for 2 days prior to behavioral training. Compared to vehicle controls, estradiol treatment enhanced place learning at a low (4.5 μg/kg) but not high dose (45 μg/kg), indicating an inverted pattern of spatial memory facilitation. Treatment with 4.4 mg of genistein over 2 days also significantly enhanced place learning over vehicle controls. For the response task, treatment with estradiol impaired learning at both low and high doses; likewise, genistein treatment impaired response learning compared to rats receiving vehicle. Overall, genistein was found to mimic estradiol-induced shifts in place and response learning, facilitating hippocampus-sensitive learning and slowing striatum-sensitive learning. These results suggest signaling through estrogen receptor β and membrane-associated estrogen receptors in learning enhancements and impairments given the preferential binding of genistein to the ERβ subtype and affinity for GPER.
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Affiliation(s)
- Samantha L Pisani
- Neuroscience Program, University of Illinois at Urbana-Champaign, 505 South Goodwin Avenue, Urbana, IL 61801, USA.
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Abstract
The current study examined the effects of gonadectomy (GDX) and subsequent testosterone treatment of male Long-Evans rats on an operant variable delay spatial alternation task (DSA). Gonadally-intact rats (intact-B), GDX rats receiving implants that delivered a physiological level of testosterone (GDX-T), and GDX rats receiving blank implants (GDX-B) were tested for 25 sessions on a DSA task with variable inter-trial delays ranging from 0 to 18 s. Acquisition of the DSA task was found to be enhanced following GDX in a time and delay dependent manner. Both the GDX-T and the intact-B rats had lower performance accuracies across delays initially, relative to GDX-B rats, and this deficit persisted into subsequent testing sessions at longer delays. The GDX-T and intact-B rats also had a tendency to commit more perseverative errors during the early testing sessions, with both groups persisting in pressing a lever which had not been associated with reinforcement for at least two consecutive trials. However, both the GDX-T and intact-B groups were able to achieve performance accuracy similar to that of the GDX-B rats by the final sessions of testing. Overall, these results suggest that castration of adult male rats enhances their acquisition of an operant DSA task.
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Affiliation(s)
- Steven L Neese
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign. 2001 S. Lincoln Avenue, Urbana, IL 61802, USA.
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Neese SL, Bandara SB, Doerge DR, Helferich WG, Korol DL, Schantz SL. Effects of multiple daily genistein treatments on delayed alternation and a differential reinforcement of low rates of responding task in middle-aged rats. Neurotoxicol Teratol 2012; 34:187-95. [PMID: 21945133 PMCID: PMC3267004 DOI: 10.1016/j.ntt.2011.09.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 08/30/2011] [Accepted: 09/06/2011] [Indexed: 01/20/2023]
Abstract
The use of extracts that are highly enriched in phytoestrogens, such as genistein, has become popular to promote various aspects of healthy aging, including maintenance of cognitive function. These compounds are promoted to menopausal women as safe, natural alternatives to traditional estrogen therapies, yet their safety and efficacy are poorly understood. Previous research in our lab found that once daily oral treatment of ovariectomized female Long-Evans (LE) rats with the soy phytoestrogen, genistein resulted in subtle deficits in performance on cognitive tasks assessing working memory and response inhibition/timing ability. The present study further modeled exposure of the menopausal woman to genistein by treating 14-month old ovariectomized female LE rats three times daily at a dose of genistein resulting in serum concentrations similar to those that could be achieved in humans consuming either a commercially available soy isoflavone supplement or a diet high in these phytoestrogens. Genistein (3.4 mg/kg) or sucrose control pellets were orally administered to animals daily, 30 min before behavioral testing, and again both 4 and 8 h after the first treatment. The test battery consisted of a delayed spatial alternation task (DSA) that tested working memory and a differential reinforcement of low rates of responding (DRL) task that tested inhibitory control/timing. Genistein treatment impaired DSA performance relative to sucrose controls. Performance on the DRL task was largely unaffected by genistein treatment. Although the impairment measured on DSA was less pronounced than that we have previously reported following chronic treatment with 17β-estradiol, the pattern of the deficit was very similar to that observed with 17β-estradiol.
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Affiliation(s)
- Steven L Neese
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, 2001 S. Lincoln Avenue, Urbana, IL 61802, USA.
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Neese SL, Clough RW, Banz WJ, Smith DC. Z-Bisdehydrodoisynolic acid (Z-BDDA): An estrogenic seco-steroid that enhances behavioral recovery following moderate fluid percussion brain injury in male rats. Brain Res 2010; 1362:93-101. [DOI: 10.1016/j.brainres.2010.09.055] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 08/24/2010] [Accepted: 09/15/2010] [Indexed: 12/20/2022]
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Neese SL, Korol DL, Katzenellenbogen JA, Schantz SL. Impact of estrogen receptor alpha and beta agonists on delayed alternation in middle-aged rats. Horm Behav 2010; 58:878-90. [PMID: 20816967 PMCID: PMC2982874 DOI: 10.1016/j.yhbeh.2010.08.017] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 08/25/2010] [Accepted: 08/26/2010] [Indexed: 10/19/2022]
Abstract
Estrogens act in the adult brain to modulate cognition, enhancing performance on some learning tests and impairing performance on others. Our previous research has revealed an impairing effect of chronic 17β-estradiol treatment in young and aged rats on a prefrontally-mediated working memory task, delayed spatial alternation (DSA). Little is known about the mechanisms of these impairing effects. The current study examined the effects of selective estrogen receptor (ER) α or ERβ activation on DSA performance in middle-aged female rats. Ovariectomized 12 month old Long-Evans (LE) rats were treated by subcutaneous injection with the ERα agonist propyl pyrazole triol (PPT) or the ERβ agonist diarylpropionitrile (DPN) at 0.02, 0.08, or 0.20mg/kg/day, or with oil vehicle and tested on an operant variable delay DSA task. A 17β-estradiol group (10% in cholesterol) was included as a positive control group. We replicated our previous finding of a 17β-estradiol induced deficit on DSA performance and this effect was paralleled by low dose (0.02mg/kg/day) DPN treatment. Higher doses of DPN failed to produce a significant change in performance. The highest dose of PPT (0.20mg/kg/day) also impaired performance, but this effect was subtle and limited to the longest delay during the final block of testing. These data confirm our earlier findings that chronic 17β-estradiol treatment has an impairing effect on the DSA task, and suggest that ERβ activation may underlie the deficit.
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Affiliation(s)
- Steven L Neese
- Neuroscience Program, University of Illinois at Urbana-Champaign, USA.
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Cimafranca MA, Davila J, Ekman GC, Andrews RN, Neese SL, Peretz J, Woodling KA, Helferich WG, Sarkar J, Flaws JA, Schantz SL, Doerge DR, Cooke PS. Acute and chronic effects of oral genistein administration in neonatal mice. Biol Reprod 2010; 83:114-21. [PMID: 20357267 DOI: 10.1095/biolreprod.109.080549] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Soy-based infant formulas are widely used in the United States and some other countries. These formulas contain high levels of the estrogenic isoflavone genistein, leading to concern that neonatal genistein exposure could cause acute and/or long-term adverse effects on reproductive and other organs. However, previous work to assess genistein effects in rodent models has not typically replicated the route of delivery and/or serum genistein concentrations reported for soy formula-fed human infants. Our objective was to develop a mouse model that more closely mimics the oral genistein exposure and total serum genistein concentrations observed in soy formula-fed infants. Mouse pups were dosed orally with genistein in a soy formula-corn oil emulsion from Postnatal Day (PND) 1 to PND 5, then effects on reproductive and non-reproductive organs were assessed after dosing and during subsequent development. Neonatal treatment resulted in changes both at the completion of dosing (PND 5) and in adult animals. At PND 5, neonatal genistein treatment caused increased relative uterine weight and down-regulation of progesterone receptor in uterine epithelia. Estrogenic effects of genistein were also seen in the neonatal ovary and thymus, which had an increase in the incidence of multioocyte follicles (MOFs) and a decrease in thymic weight relative to body weight, respectively. The increased incidence of MOFs persisted into adulthood for neonatally treated genistein females, and estrous cycle abnormalities were seen at 6 mo of age despite normal fertility in these mice. The immediate and long-term effects in this neonatal animal model raise concerns that high serum concentrations of genistein are estrogenic and could potentially impact the development of human infants fed soy formula.
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Affiliation(s)
- Melissa A Cimafranca
- Department of Veterinary Biosciences, Division of Nutritional Sciences, University of Illinois, 2001 S. Lincoln Ave., Urbana, IL 61802, USA
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Neese SL, Wang VC, Doerge DR, Woodling KA, Andrade JE, Helferich WG, Korol DL, Schantz SL. Impact of dietary genistein and aging on executive function in rats. Neurotoxicol Teratol 2010; 32:200-11. [PMID: 19945528 PMCID: PMC2860723 DOI: 10.1016/j.ntt.2009.11.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 11/10/2009] [Accepted: 11/19/2009] [Indexed: 12/29/2022]
Abstract
Genistein is an estrogenic soy isoflavone widely promoted for healthy aging, but its effects on cognitive function are not well-understood. We examined the cognitive effects of once daily oral genistein treatment at two doses (approximately 162 microg/kg/day low dose and a 323 microg/kg/day high dose) in ovariectomized young (7 month), middle-aged (16 month), and old (22 month) Long-Evans rats. Operant tasks including delayed spatial alternation (DSA), differential reinforcement of low rates of responding (DRL), and reversal learning that tap prefrontal cortical function were used to assess working memory, inhibitory control/timing, and strategy shifting, respectively. At the conclusion of cognitive testing, brains were collected and relative densities of D1 and D2 dopamine receptors and dopamine transporter (DAT) were measured in the prefrontal cortex. On the DSA task, the high dose old group performed worse than both the high dose young and middle-aged groups. On the DRL task, the high dose of genistein resulted in a marginally significant impairment in the ratio of reinforced to non-reinforced lever presses. This effect was present across age groups. Age effects were also found as old rats performed more poorly than the young and middle-aged rats on the DSA overall. In contrast, middle-aged and old rats made fewer lever presses on the DRL than did the young rats, a pattern of behavior associated with better performance on this task. Moreover, while DAT levels overall decreased with age, genistein treatment produced an increase in DAT expression in old rats relative to similarly aged control rats. D1 and D2 densities did not differ between genistein dose groups or by age. These results highlight the fact that aspects of executive function are differentially sensitive to both genistein exposure and aging and suggest that altered prefrontal dopamine function could potentially play a role in mediating these effects.
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Affiliation(s)
- Steven L. Neese
- Department of Veterinary Sciences, University of Illinois at Urbana-Champaign. 2001 S. Lincoln Avenue, Urbana, IL 61802, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign. 505 South Goodwin Avenue, Urbana, IL 61801, USA
| | - Victor C. Wang
- Department of Veterinary Sciences, University of Illinois at Urbana-Champaign. 2001 S. Lincoln Avenue, Urbana, IL 61802, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign. 505 South Goodwin Avenue, Urbana, IL 61801, USA
| | - Daniel R. Doerge
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration. 3900 NCTR Road, Jefferson, AR 72079-9502, USA
| | - Kellie A. Woodling
- Division of Biochemical Toxicology, National Center for Toxicological Research, U.S. Food and Drug Administration. 3900 NCTR Road, Jefferson, AR 72079-9502, USA
| | - Juan E. Andrade
- Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign. 905 S. Goodwin Avenue, Urbana, IL 61801, USA
| | - William G. Helferich
- Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign. 905 S. Goodwin Avenue, Urbana, IL 61801, USA
| | - Donna L. Korol
- Neuroscience Program, University of Illinois at Urbana-Champaign. 505 South Goodwin Avenue, Urbana, IL 61801, USA
- Department of Psychology, University of Illinois at Urbana-Champaign. 603 East Daniel Street, Champaign, IL 61820, USA
- Institute for Genomic Biology Department of Veterinary Sciences, University of Illinois at Urbana-Champaign. 1206 West Gregory Drive, Urbana, IL 61801, USA
| | - Susan L. Schantz
- Department of Veterinary Sciences, University of Illinois at Urbana-Champaign. 2001 S. Lincoln Avenue, Urbana, IL 61802, USA
- Neuroscience Program, University of Illinois at Urbana-Champaign. 505 South Goodwin Avenue, Urbana, IL 61801, USA
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Wang VC, Neese SL, Korol DL, Schantz SL. Chronic estradiol replacement impairs performance on an operant delayed spatial alternation task in young, middle-aged, and old rats. Horm Behav 2009; 56:382-90. [PMID: 19631212 PMCID: PMC2761498 DOI: 10.1016/j.yhbeh.2009.07.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 06/24/2009] [Accepted: 07/14/2009] [Indexed: 12/23/2022]
Abstract
The current study examined effects of chronic estradiol replacement on a prefrontally-mediated working memory task at different ages in a rodent model. Ovariectomized young, middle-aged, and old Long-Evans rats were given 5% or 10% 17beta-estradiol in cholesterol vehicle via Silastic implants and tested on an operant delayed spatial alternation task (DSA). The two estradiol exposed groups did not perform as well as the vehicle control group did. Deficits were present at all but the longest delay, where all groups including the vehicle control group performed poorly. Surprisingly, there was not a significant effect of age or an age by estradiol interaction, despite the fact that old rats had longer latencies to respond after both correct and incorrect lever presses. These data confirm our earlier finding that chronic estradiol treatment has an impairing effect on working memory as measured on DSA task. However, contrary to expectations, young, middle-aged and old rats were similarly impaired by chronic estradiol treatment; there were no indications of differential effects at different periods of the lifespan. Also contrary to expectations, there were no indications of a decline in DSA performance with advancing age. Overall, the results demonstrate that chronic estradiol exposure causes deficits in the DSA performance of ovariectomized female rats, not only in young adulthood, but also at older ages analogous to those at which hormone replacement therapy is commonly prescribed in humans.
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Affiliation(s)
- Victor C. Wang
- Neuroscience Program and Department of Veterinary Sciences, University of Illinois at Urbana-Champaign
| | - Steven L. Neese
- Neuroscience Program and Department of Veterinary Sciences, University of Illinois at Urbana-Champaign
| | - Donna L. Korol
- Neuroscience Program, Department of Psychology, and Institute for Genomic Biology, University of Illinois at Urbana-Champaign
| | - Susan L. Schantz
- Neuroscience Program and Department of Veterinary Sciences, University of Illinois at Urbana-Champaign
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Clough RW, Neese SL, Sherill LK, Tan AA, Duke A, Roosevelt RW, Browning RA, Smith DC. Cortical edema in moderate fluid percussion brain injury is attenuated by vagus nerve stimulation. Neuroscience 2007; 147:286-93. [PMID: 17543463 DOI: 10.1016/j.neuroscience.2007.04.043] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 04/23/2007] [Accepted: 04/27/2007] [Indexed: 11/16/2022]
Abstract
Development of cerebral edema (intracellular and/or extracellular water accumulation) following traumatic brain injury contributes to mortality and morbidity that accompanies brain injury. Chronic intermittent vagus nerve stimulation (VNS) initiated at either 2 h or 24 h (VNS: 30 s train of 0.5 mA, 20 Hz, biphasic pulses every 30 min) following traumatic brain injury enhances recovery of motor and cognitive function in rats in the weeks following brain injury; however, the mechanisms of facilitated recovery are unknown. The present study examines the effects of VNS on development of acute cerebral edema following unilateral fluid percussion brain injury (FPI) in rats, concomitant with assessment of their behavioral recovery. Two hours following FPI, VNS was initiated. Behavioral testing, using both beam walk and locomotor placing tasks, was conducted at 1 and 2 days following FPI. Edema was measured 48 h post-FPI by the customary method of region-specific brain weights before and after complete dehydration. Results of this study replicated that VNS initiated at 2 h after FPI: 1) effectively facilitated the recovery of vestibulomotor function at 2 days after FPI assessed by beam walk performance (P<0.01); and 2) tended to improve locomotor placing performance at the same time point (P=0.18). Most interestingly, results of this study showed that development of edema within the cerebral cortex ipsilateral to FPI was significantly attenuated at 48 h in FPI rats receiving VNS compared with non-VNS FPI rats (P<0.04). Finally, a correlation analysis between beam walk performance and cerebral edema following FPI revealed a significant inverse correlation between behavior performance and cerebral edema. Together, these results suggest that VNS facilitation of motor recovery following experimental brain injury in rats is associated with VNS-mediated attenuation of cerebral edema.
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Affiliation(s)
- R W Clough
- Department of Anatomy, Southern Illinois University School of Medicine, Carbondale, IL 62901-6503, USA.
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Neese SL, Sherill LK, Tan AA, Roosevelt RW, Browning RA, Smith DC, Duke A, Clough RW. Vagus nerve stimulation may protect GABAergic neurons following traumatic brain injury in rats: An immunocytochemical study. Brain Res 2006; 1128:157-63. [PMID: 17125748 PMCID: PMC1892906 DOI: 10.1016/j.brainres.2006.09.073] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Revised: 09/21/2006] [Accepted: 09/21/2006] [Indexed: 11/21/2022]
Abstract
Seizures and subclinical seizures occur following experimental brain injury in rats and may result from inhibitory neuron loss. This study numerically compares cortical and hippocampal glutamic acid decarboxylase (GAD) positive neurons between sham fluid percussion injury (FPI), FPI with sham Vagus Nerve Simulation (VNS), and FPI with chronic intermittent VNS initiated at 24 h post FPI in rats. Rats (n=8/group) were prepared for immunocytochemistry of GAD at 15 days post FPI. Serial sections were collected and GAD immunoreactive neurons were counted in the hippocampal hilus and two levels of the cerebral cortex. Numbers of quantifiable GAD cells in the rostral cerebral cortices were different between groups, both ipsilateral and contralateral to the FPI. Post hoc analysis of cell counts rostral to the ipsilateral epicenter, revealed a significant 26% reduction in the number of GAD cells/unit area of cerebral cortex following FPI. In the FPI-VNS group, this percentage loss was attenuated to only an 8.5% reduction, a value not significantly different from the sham group. In the contralateral side of the rostral cerebral cortex, FPI induced a significant 24% reduction in GAD cells/unit area; whereas, the VNS-treated rats showed no appreciable diminution of GAD cells rostral to the contralateral epicenter. Hippocampal analysis revealed a similar reduction of GAD cells in the FPI group; however, unlike the cortex this was not statistically significant. In the FPI-VNS group, a trend towards increased numbers of hilar GAD cells was observed, even over and above that of the sham FPI group; however, this was also not statistically significant. Together, these data suggest that VNS protects cortical GAD cells from death subsequent to FPI and may increase GAD cell counts in the hippocampal hilus of the injured brain.
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Affiliation(s)
- Steven L. Neese
- Brain and Cognitive Sciences Program, Department of Psychology, Southern Illinois University, Carbondale, IL 62901-6503
| | - Luke K. Sherill
- Brain and Cognitive Sciences Program, Department of Psychology, Southern Illinois University, Carbondale, IL 62901-6503
| | - Arlene A. Tan
- Brain and Cognitive Sciences Program, Department of Psychology, Southern Illinois University, Carbondale, IL 62901-6503
| | - Rodney W. Roosevelt
- Brain and Cognitive Sciences Program, Department of Psychology, Southern Illinois University, Carbondale, IL 62901-6503
| | - Ronald A. Browning
- Department of Physiology, Southern Illinois University School of Medicine Carbondale, Carbondale, IL 62901-6503
- SIU Center for Integrated Research in Cognitive and Neural Sciences, Southern Illinois University, Carbondale, IL 62901-6503
| | - Douglas C. Smith
- Brain and Cognitive Sciences Program, Department of Psychology, Southern Illinois University, Carbondale, IL 62901-6503
- Department of Physiology, Southern Illinois University School of Medicine Carbondale, Carbondale, IL 62901-6503
- SIU Center for Integrated Research in Cognitive and Neural Sciences, Southern Illinois University, Carbondale, IL 62901-6503
| | - Andrea Duke
- Brain and Cognitive Sciences Program, Department of Psychology, Southern Illinois University, Carbondale, IL 62901-6503
| | - Rich W. Clough
- Department of Anatomy, Southern Illinois University School of Medicine Carbondale, Carbondale, IL 62901-6503
- SIU Center for Integrated Research in Cognitive and Neural Sciences, Southern Illinois University, Carbondale, IL 62901-6503
- *Corresponding author: Rich W. Clough, Ph.D. Department of Anatomy, Southern Illinois University School of Medicine Carbondale, Carbondale, IL 62901-6503, 618-453-1571 (w), 618-453-1527 (fax),
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Smith DC, Tan AA, Duke A, Neese SL, Clough RW, Browning RA, Jensen RA. Recovery of Function after Vagus Nerve Stimulation Initiated 24 Hours after Fluid Percussion Brain Injury. J Neurotrauma 2006; 23:1549-60. [PMID: 17020489 DOI: 10.1089/neu.2006.23.1549] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Recent evidence from our laboratory demonstrated in laboratory rats that stimulation of the vagus nerve (VNS) initiated 2 h after lateral fluid percussion brain injury (FPI) accelerates the rate of recovery on a variety of behavioral and cognitive tests. VNS animals exhibited a level of performance comparable to that of sham-operated uninjured animals by the end of a 2-week testing period. The effectiveness of VNS was further evaluated in the present study in which initiation of stimulation was delayed until 24 h post-injury. Rats were subjected to a moderate FPI and tested on the beam walk, skilled forelimb reaching, locomotor placing, forelimb flexion and Morris water maze tasks for 2 weeks following injury. VNS (30 sec trains of 0.5 mA, 20.0-Hz biphasic pulses) was initiated 24 h post-injury and continued at 30-min intervals for the duration of the study, except for brief periods when the animals were detached for behavioral assessments. Consistent with our previous findings when stimulation was initiated 2 h post-injury, VNS animals showed significantly faster rates of recovery compared to controls. By the last day of testing (day 14 post-injury), the FPI-VNS animals were performing significantly better than the FPI-no-VNS animals and were not significantly different from shams in all motor and sensorimotor tasks. Performance in the Morris water maze indicated that the VNS animals acquired the task more rapidly on days 11-13 post-injury. On day 14, the FPI-VNS animals did not differ in the latency to find the platform from sham controls, whereas the injured controls did; however, the FPI-VNS animals and injured controls were not significantly different. Despite the lack of significant histological differences between the FPI groups, VNS, when initiated 24 h following injury, clearly attenuated the ensuing behavioral deficits and enhanced acquisition of the cognitive task. The results are discussed with respect to the norepinephrine hypothesis.
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Affiliation(s)
- Douglas C Smith
- Brain and Cognitive Sciences Program, Department of Psychology, Southern Illinois University, Carbondale, Illinois 62901-6502, USA.
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Smith DC, Modglin AA, Roosevelt RW, Neese SL, Jensen RA, Browning RA, Clough RW. Electrical stimulation of the vagus nerve enhances cognitive and motor recovery following moderate fluid percussion injury in the rat. J Neurotrauma 2005; 22:1485-502. [PMID: 16379585 PMCID: PMC1769332 DOI: 10.1089/neu.2005.22.1485] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Intermittent, chronically delivered electrical stimulation of the vagus nerve (VNS) is an FDA-approved procedure for the treatment of refractory complex/partial epilepsy in humans. Stimulation of the vagus has also been shown to enhance memory storage processes in laboratory rats and human subjects. Recent evidence suggests that some of these effects of VNS may be due to the activation of neurons in the nucleus locus coeruleus resulting in the release of norepinephrine (NE) throughout the neuraxis. Because antagonism of NE systems has been shown to delay recovery of function following brain damage, it is possible that enhanced release of NE in the CNS may facilitate recovery of function. To evaluate this hypothesis the lateral fluid percussion injury (LFP) model of traumatic brain injury was used and a variety of motor and cognitive behavioral tests were employed to assess recovery in pre-trained stimulated, control, and sham-injured laboratory rats. Two hours following moderate LFP, vagus nerve stimulation (30.0-sec trains of 0.5 mA, 20.0 Hz, biphasic pulses) was initiated. Stimulation continued in each animal's home cage at 30-min intervals for a period of 14 days, with the exception of brief periods when the animals were disconnected for behavioral assessments. Motor behaviors were evaluated every other day following LFP and tests included beam walk, locomotor placing, and skilled forelimb reaching. In each measure an enhanced rate of recovery and /or level of final performance was observed in the VNS-LFP animals compared to nonstimulated LFP controls. Behavior in the Morris water maze was assessed on days 11-14 following injury. Stimulated LFP animals showed significantly shorter latencies to find the hidden platform than did controls. Despite these behavioral effects, neurohistological examination did not reveal significant differences in lesion extent, density of fluorojade positive neurons, reactive astrocytes or numbers of spared neurons in the CA3 subarea of the hippocampus, at least at the one time point studied 15 days post-injury. These results support the idea that vagus nerve stimulation enhances the neural plasticity that underlies recovery of function following brain damage and provides indirect support for the hypothesis that enhanced NE release may mediate the effect. Importantly, since VNS facilitated both the rate of recovery and the extent of motor and cognitive recovery, these findings suggest that electrical stimulation of the vagus nerve may prove to be an effective non-pharmacological treatment for traumatic brain injury.
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Affiliation(s)
- Douglas C Smith
- Brain & Cognitive Sciences Program, Department of Psychology, Southern Illinois University School of Medicine, Carbondale, IL 62901-6502, USA.
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