PubMed · 6509219
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J Milic-Emili. Loaded breathing.. https://pubmed.ncbi.nlm.nih.gov/6509219/
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BACKGROUND: Transthoracic echocardiography (M-mode and Doppler) offers a noninvasive approach for in vivo evaluation of the mouse heart. The present study examines its usefulness for assessing the morphological/functional phenotype of the left ventricle (LV) in several transgenic and surgical murine models of cardiac disease. METHODS AND RESULTS: Observations were made in 83 intact, anesthetized mice. In mice with a surgical arteriovenous fistula, volume overload and LV dilation were detected. In normal mice, echocardiographic indexes of increased contractility (dobutamine) were confirmed by LV dP/dtmax. In transgenic mice with overexpression of the beta 2-adrenergic receptor, heart rate and mean velocity of circumferential fiber shortening were increased, indicating enhanced contractility. In colony screening of transgenic mice overexpressing the H-ras gene, 45% had increased LV wall thickness (> 0.9 mm), and those showing a striking increase were selected for breeding. In mice with LV hypertrophy (aortic constriction) and normal mice, the actual LV mass determined by echocardiography correlated well (r = .93), and 95% confidence limits were determined. The maximum intraobserver and interobserver coefficients of variation for M-mode data were 0.03 +/- 0.29 mm (+/- 2 SD), < 10% for LV internal dimensions but 27% to 30% for wall thickness. CONCLUSIONS: These studies provide the first application of transthoracic echocardiography for morphological/functional characterization of the cardiac phenotype in transgenic and surgical murine models, including (1) high reliability for detecting LV chamber dilation and function; (2) reliability (and its limits) for determining abnormal LV wall thickness and LV mass; (3) identification of marked, sometimes asymmetrical, hypertrophy in a transgenic model of hypertrophic cardiomyopathy; and (4) usefulness for transgenic colony screening to identify markedly abnormal phenotypes.
The possibility that single electrical shock stimulation of somatic afferent nerves could evoke a reflex response in vagal efferent nerves innervating the stomach was examined using anesthetized, artificially-ventilated rats. A single shock to a hindlimb afferent nerve (tibial nerve) produced two distinct reflex components in gastric vagal efferent nerves; namely (1) A-reflex discharges with a latency of about 120 ms and a duration of about 200 ms elicited by stimulation of myelinated A afferent fibers, and (2) C-reflex discharges with a latency of about 360 ms and a duration of about 200 ms elicited by stimulation of unmyelinated C afferent fibers. A single shock to a first lumbar spinal afferent nerve produced only a week reflex component with a latency of about 120 ms and a duration of about 190 ms in gastric vagal efferent nerves. Limb afferents appear to have stronger central pathways functionally connecting to gastric vagal efferent preganglionic neurons in the brainstem, than do abdominal afferents.
In this study, we characterized the cardiovascular effects produced by microinjection of doses in the femtomole range of bradykinin (BK) into the nucleus tractus solitarii of male Wistar rats (230-280 g, n = 120) anesthetized with urethane (1.2 g/kg, i.p.). Microinjections of BK (1, 10, 100 fmol, and 1 and 10 pmol, in 50 nl) or vehicle (NaCl, 0.9%) were made by using a triple-barreled glass micropipette into the medial nTS (0.4 mm anterior, 0.3 mm lateral to the obex and 0.3 mm deep from the dorsal surface). Microinjection of BK produced a shallow dose-dependent decrease in mean arterial pressure and heart rate reaching -18 +/- 6 mmHg and -21 +/- 5 beats/min, with the dose of 10 pmol. The peripheral mechanism of these effects, tested in animals treated with methylatropine (2 mg/kg, i.v.), or propranolol (2 mg/kg, i.v.) or prazosin (30 micrograms/kg, i.v.), was shown to be mainly dependent on an increase in vagal efferent activity for bradycardia and a decrease in sympathetic activity for hypotension. In order to investigate the receptor subtype involved in these effects, BK was microinjected into the nTS before and after the injection of the B1 receptor antagonist, Des-Arg9-Leu8-BK (DALBK) (11.5 pmol) or before and after the B2 receptor antagonist, HOE-140 (7.7 pmol). The cardiovascular effects of BK were significantly attenuated by the microinjection of HOE-140 and DALBK into the nTS. The effect of BK microinjected into the nTS on the baroreflex modulation was also investigated. While BK produced a significant facilitation of the baroreflex, HOE-140 and DALBK produced a significant attenuation of the baroreceptor control of heart rate. Taken together, the data presented in this study indicate the nTS as a site, in the central nervous system, for the modulatory effect of BK on the central cardiovascular control.