Mechanisms involved in the cardiovascular effects caused by acute osmotic stimulation in conscious rats

Figures & data

Table 1. Baseline means arterial pressure (MAP), heart rate (HR), before treatment (i.v.), and before osmotic stimulation.

Treatment	MAP (mmHg) ± SEM			HR (bpm) ± SEM
	Before treatment	Before OS	t=; p=	Before treatment	Before OS	t=; p=	n
Vehicle (saline 0.9%)	98 ± 2	97 ± 2.3	t = 0.13; p = 0.89	381 ± 10	369 ± 13	t = 0.73; p = 0.47	n = 8
Pentolinium (5 mg/kg)	99 ± 0.9	65 ± 2*	t = 15.27; p < 0.0001	364 ± 8.5	357 ± 13	t = 0.48; p = 0.63	n = 5
Vehicle (saline 0.9%)	102 ± 2	100 ± 1.1	t = 1.15; p = 0.26	367 ± 10.3	363 ± 5.4	t = 0.34; p = 0.73	n = 6
Prazosin (0.5 mg/kg)	94 ± 3	88 ± 2	t = 1.40; p = 0.19	378 ± 24.9	395 ± 16.2	t = 0.54; p = 0.59	n = 5
Atenolol (1 mg/kg)	102 ± 1.4	98 ± 3.1	t = 1.33; p = 0.23	344 ± 10	350 ± 14	t = 0.34; p = 0.74	n = 4
Vehicle (saline 0.9%)	100 ± 0.2	101 ± 0.3	t = 1.96; p = 0.07	365 ± 8.7	369 ± 12	t = 0.28; p = 0.78	n = 6
dTyr (50 µg/kg)	102 ± 4	106 ± 2	t = 0.13; p > 0.05	362 ± 16	365 ± 12.9	t = 0.10; p > 0.05	n = 6
Vehicle (saline 0.9%)	101 ± 0.9	100 ± 3	t = 0.93; p > 0.05	354 ± 15	362 ± 18	t = 0.39; p > 0.05	n = 6
Atosiban (10µg/kg)	102 ± 0.9	97 ± 3	t = 0.93; p > 0.05	340 ± 20.5	331 ± 5.8	t = 0.39; p > 0.05	n = 5

Baseline MAP and HR values correspond to the average of 1-min recording just before respectively the treatment with vehicle or drugs, and the intraperitoneal injection of hypertonic saline (OS).

^* Statically different from baseline values recorded before treatment, Student’s t test, p < 0.05.

Figure 1. (A) Time course of the mean arterial pressure (ΔMAP) and heart rate (ΔHR) responses observed after intraperitoneal (i.p.) injection of isotonic saline (0.15 M NaCl, n = 4) or hypertonic saline (0.6 M NaCl, n = 4). The onset of osmotic stimulation (OS) was at time 0 min. (*) indicates significantly different from control, Two-way ANOVA, P < 0.05. (B) Representative recordings of mean arterial pressure (MAP), pulsatile arterial pressure (PAP) and heart rate (HR) showing the cardiovascular effects to OS i.p. injection (0.6 M NaCl) in one unanesthetized rat. The onset of OS i.p. injection is indicated by an arrow at time 0 min.

Figure 2. Plasma osmolality, plasma NaCl concentration, urinary volume, and NaCl concentration were measured 30min after the onset of OS with either i.p. injection of isotonic saline (0.15 M NaCl, n = 5) or hypertonic saline (0.6 M NaCl, n = 6) in conscious rats. (*) indicates significant difference, Student's t-test, P < 0.05.

Figure 3. Left -Time course curves of mean arterial pressure (MAP) and heart rate (HR) responses observed after acute OS i.p. injection (0.6 M NaCl) in animals pretreated with either vehicle solution (1 mL/kg i.v. n = 8) or pentolinium (5 mg/kg, i.v. n = 5). Right - Time course showing absolute mean arterial pressure MAP and HR values. Left - Time course showing changes in mean arterial pressure (ΔMAP) and heart rate (ΔHR) responses. Drugs were injected at the time -10 min. The onset of OS was at time 0min. (*) indicates significantly different from control, Two-way ANOVA, P < 0.05.

Figure 4. Time course curves of mean arterial pressure (ΔMAP) and heart rate (ΔHR) responses observed after acute OS i.p. injection (0.6 M NaCl) in animals pretreated with either vehicle (1 mL/kg i.v. n = 6) or prazosin (0.5 mg/kg, i.v. n = 5). Drugs were injected at the time -10 min. The onset of OS was at time 0 min. (*) indicates significantly different from control, Two-way ANOVA, P < 0.05.

Figure 5. Time course curves of mean arterial pressure (ΔMAP) and heart rate (ΔHR) responses observed after acute OS i.p. injection (0.6 M NaCl) in animals pretreated with either vehicle (1 mL/kg i.v. n = 6) or atenolol (1 mg/kg, i.v. n = 4). Drugs were injected at the time -10 min. The onset of OS was at time 0 min. (*) indicates significantly different from control, Two-way ANOVA, P < 0.05.

Figure 6. Time course curves of mean arterial pressure (ΔMAP) and heart rate (ΔHR) responses observed after acute OS i.p. injection (0.6 M NaCl) in animals pretreated with either vehicle (1 mL/kg i.v. n = 6) or dTyr(CH2)5(Me)AVP (50 μg/kg, i.v. n = 6). Drugs were injected at the time -10 min. The onset of OS was at time 0 min. (*) indicates significantly different from control, Two-way ANOVA, P < 0.05.

Figure 7. Time course curves of mean arterial pressure (ΔMAP) and heart rate (ΔHR) responses observed after acute OS i.p. injection (0.6 M NaCl) in animals pretreated with either vehicle (1 mL/kg i.v. n=6) or Atosiban (10 μg/kg, i.v. n = 5). Drugs were injected at the time -10 min. The onset of OS was at time 0 min. (*) indicates significantly different from control, Two-way ANOVA, P < 0.05.