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Surprisingly, however, a recent study in anesthetized rats paradoxically found an enhancement of cardiac vagal activity during inspiration, suggesting that rats have an inverted respiratory sinus arrhythmia (Rentero N, Cividjian A, Trevaks D, Pequignot JM, Quintin L, and McAllen RM. Am J Physiol Regul Integr Comp Physiol 283: R1327\u2013R1334, 2002). To address this controversy, this study examined respiratory sinus arrhythmia in conscious freely moving rats and tested whether the commonly used experimental anesthetics urethane, pentobarbital sodium, or ketamine-xylazine alter respiratory sinus arrhythmia. Heart rate significantly increased 21 beats\/min during inspiration in conscious rats, a pattern similar to the respiratory sinus arrhythmia that occurs in other species. However, anesthetics altered normal respiratory sinus arrhythmia. Ketamine-xylazine (87 mg\/kg and 13 mg\/kg) depressed and pentobarbital sodium (60 mg\/kg) abolished normal respiratory sinus arrhythmia. Urethane (1 g\/kg) inverted the cardiorespiratory pattern so that heart rate significantly decreased during inspiration. Our study demonstrates that heart rate normally increases during inspiration in conscious, freely moving rats, similar to the respiratory sinus arrhythmia pattern that occurs in other species but that this pattern is disrupted in the presence of general anesthetics, including inversion in the case of urethane. The presence and consequences of anesthetics need to be considered in studying the parasympathetic control of heart rate.<\/jats:p>","DOI":"10.1152\/japplphysiol.00277.2004","type":"journal-article","created":{"date-parts":[[2004,5,25]],"date-time":"2004-05-25T00:58:25Z","timestamp":1085446705000},"page":"1431-1436","source":"Crossref","is-referenced-by-count":48,"title":["Respiratory sinus arrhythmia in freely moving and anesthetized rats"],"prefix":"10.1152","volume":"97","author":[{"given":"Evguenia","family":"Bouairi","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Robert","family":"Neff","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cory","family":"Evans","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Allison","family":"Gold","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael C.","family":"Andresen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David","family":"Mendelowitz","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"24","reference":[{"key":"R1","doi-asserted-by":"publisher","DOI":"10.1098\/rspb.1936.0006"},{"key":"R2","doi-asserted-by":"publisher","DOI":"10.1097\/00005344-199001000-00002"},{"key":"R3","unstructured":"Bedran-de-Castro MT, Farah VM, and Krieger EM.Influence of general anesthetics on baroreflex control of circulation. 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