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First published online March 8, 2005
Journal of Experimental Biology 208, 821-829 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01470

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Baroreflex mediated control of heart rate and vascular capacitance in trout

E. Sandblom^* and M. Axelsson

Department of Zoology, Göteborg University, Box 463, S-405 30 Gothenburg, Sweden

View larger version (28K): [in a new window]   Fig. 1. Schematic drawing of trout instrumented with (a) occlusion catheter in dorsal aorta (Da), positioned distal to celiacomesenteric artery (CMa); (b) catheter in sinus venosus (Sv); (c) percutaneous ECG-electrodes and (d) occlusion probe around ventral aorta (Va). A cross-section of the ventral aortic probe is magnified to illustrate (i) PE-50 catheter connected to latex-balloon; (ii) inflatable latex-balloon and (iii) doppler crystal with lead.

View larger version (18K): [in a new window]   Fig. 3. Representative original recordings of dorsal aortic blood pressure (Pda) from one trout before treatment (A) and after prazosin (1 mg kg–1) treatment (B). 30 s of pre-branchial occlusion starts at a and stops at b followed by a mean circulatory filling pressure manoeuvre between c and d. White bars represent 10 s mean values + S.E.M. of Pda prior to occlusion and black bars represent 10 s mean values + S.E.M. of Pda immediately following the mean circulatory filling pressure manoeuvre. *Statistically significant difference (Px0.05) between values. Note the reflex increase in pressure during occlusion and the following increase in pressure in the untreated fish. After prazosin treatment this reflex response is absent.

View larger version (27K): [in a new window]   Fig. 4. Representative original recordings of heart rate (fH), dorsal aortic pressure (Pda) and venous pressure (Pven) from an untreated trout. Left-hand panels demonstrate a pre-branchial occlusion (Pre) and right-hand panels demonstrate a post-branchial occlusion (Post). Both occlusions are followed by a mean circulatory filling pressure manoeuvre (MCFP).

View larger version (20K): [in a new window]   Fig. 2. Heart rate (A; fH) and mean circulatory filling pressure (B; MCFP) in untreated, prazosin-treated (1 mg kg–1) and atropine+prazosin treated trout (1 mg kg–1 and 1.2 mg kg–1, respectively) during control conditions (white bars), post-(grey bars) and pre-branchial occlusion (black bars). Control heart rate represents pooled mean values + S.E.M. of 120 s prior to occlusion. Heart rate during post- and pre-branchial occlusion are mean values + S.E.M. of the last 20 s of the 30 s occlusion. MCFP is measured in unstimulated fish and immediately following 30 s of stimulation with post- or pre-branchial occlusion. Statistically significant difference *from the control within each treatment and for control values between treatments (Px0.05).