| Abstract: | Hyperammonemia, arising from variety of disorders, leads to severe neurological dysfunction. The mechanisms of ammonia toxicity in brain are not completely understood. This study investigated the effects of ammonia on monoaminergic systems in brains of fathead minnows (Pimephales promelas). Fish serve as a good model system to investigate hyperammonemic effects on brain function since no liver manipulations are necessary to increase endogenous ammonia concentrations. Using high performance liquid chromatography with electrochemical detection, monoamines and some associated metabolites were measured from whole brain homogenate. Adult males were exposed for 48??h to six different concentrations of ammonia (0.01-2.36??mg/l unionized) which bracketed the 96-h LC50 for this species. Ammonia concentration-dependent decreases were found for the catecholamines (norepinephrine and dopamine) and the indoleamine serotonin (5-HT). After an initial increase in the 5-HT precursor 5-hydroxytryptophan it too decreased with increasing ammonia concentrations. There were also significant increases in the 5-HIAA/5-HT and DOPAC/DA ratios, often used as measures of turnover. There were no changes in epinephrine (Epi) or monoamine catabolites (DOPAC, 5-HIAA) at any ammonia concentrations tested. Results suggest that ammonia causes decreased synthesis while also causing increased release and degradation. Increased release may underlie behavioral reactions to ammonia exposure in fish. This study adds weight to a growing body of evidence demonstrating that ammonia leads to dysfunctional monoaminergic systems in brain which may underlie neurological symptoms associated with human disorders such as hepatic encephalopathy. ?? 2007 Elsevier B.V. All rights reserved. |
| Genre: | Article |
| ProdID: | 70029970 |
| Citation Author: | Ronan, P. J.; Gaikowski, M. P.; Hamilton, S. J.; Buhl, K. J.; Summers, C. H. |
| Citation Contributing Office: | |
| Citation Datum: | |
| Citation Day: | |
| Citation Edition: | |
| Citation Editor: | |
| Citation End Page: | 191 |
| Citation Issue: | 1 |
| Citation Keywords: | |
| Citation Language: | English |
| Citation Larger Work Title: | Brain Research |
| Citation LatN: | |
| Citation LatS: | |
| Citation LonE: | |
| Citation LonW: | |
| Citation Month: | |
| Citation No Pagination: | |
| Citation Number Of Pages: | 8 |
| Citation Online Only Flag: | |
| Citation Phsyical Description: | |
| Citation Projection: | |
| Citation Public Comments: | |
| Citation Publisher: | |
| Citation Series: | |
| Citation Series Code: | |
| Citation Series Number: | |
| Citation Search Results Text: | Ammonia causes decreased brain monoamines in fathead minnows (Pimephales promelas); 2007; Article; Journal; Brain Research; Ronan, P. J.; Gaikowski, M. P.; Hamilton, S. J.; Buhl, K. J.; Summers, C. H. |
| Citation Start Page: | 184 |
| Citation Volume: | 1147 |
| Citation Year: | 2007 |
| Type: | citation/reference |
| Text: | Ammonia causes decreased brain monoamines in fathead minnows (Pimephales promelas); 2007; Article; Journal; Brain Research; Ronan, P. J.; Gaikowski, M. P.; Hamilton, S. J.; Buhl, K. J.; Summers, C. H. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1016/j.brainres.2007.02.015 |
| Date Other: | Mon, 1 Jan 2007 00:00 -0600 |
| Publisher: | |
