Central oxytocin modulation of acute stress-induced cardiovascular responses after myocardial infarction in the rat

Figures & data

Table I.  MABP and HR before (0 min) and after 40 min of ICV infusion of 0.9% NaCl (control), oxytocin or oxytocin receptor antagonist in conscious sham-operated rats, and rats after myocardial infarction.

Experimental group and ICV infusion	MABP (mm Hg), 0 min	MABP (mm Hg), 40 min	HR (beats/min), 0 min	HR (beats/min), 40 min	LVEDP (mm Hg)
Sham-operated + ICV 0.9% NaCl	105 ± 3.2 (n = 7)	111 ± 2.8 (n = 7)	372 ± 10.2 (n = 7)	375 ± 10.1 (n = 7)	4.3 ± 0.7 (n = 6)
Sham-operated + ICV oxytocin	111 ± 2.6 (n = 6)	109 ± 4.4 (n = 6)	369 ± 8.7 (n = 6)	368 ± 6.7 (n = 6)	4.4 ± 0.5 (n = 5)
Sham-operated + ICV oxytocin antagonist	112 ± 1.9 (n = 7)	114 ± 2.5 (n = 7)	367 ± 10.4 (n = 7)	371 ± 10.3 (n = 7)	3.8 ± 0.8 (n = 6)
Infarcted + ICV 0.9% NaCl	104 ± 3.5 (n = 8)	105 ± 3.4 (n = 8)	381 ± 6.6 (n = 8)	381 ± 5.9 (n = 8)	24.7 ± 2.0* (n = 6)
Infarcted + ICV oxytocin	105 ± 3.2 (n = 6)	105 ± 4.0 (n = 6)	376 ± 9.0 (n = 6)	375 ± 8.7 (n = 6)	24.5 ± 1.8* (n = 6)
Infarcted + ICV oxytocin antagonist	103 ± 3.5 (n = 6)	105 ± 3.1 (n = 6)	381 ± 9.8 (n = 6)	382 ± 10.3 (n = 6)	22.7 ± 1.7* (n = 6)

LVEDP was measured in anaesthetised rats at the end of experiments. Means ± SEM are shown; n, number of rats. *Significant differences between LVEDP in the infarcted and the respective sham-operated groups of rats, P < 0.001.

Figure 1  Non-significant changes of MABP and HR from baseline under resting conditions in the sham-operated (open symbols) and infarcted (filled symbols) rats receiving ICV infusions of 0.9% NaCl (triangles), OXYANT (squares) or oxytocin (OXY, circles). The arrow indicates the start of ICV infusion. Number of rats per group: sham-operated 0.9%: n = 7; sham-operated OXY: n = 6; sham-operated OXYANT: n = 7; infarcted 0.9% NaCl: n = 8; infarcted OXY: n = 6; infarcted OXYANT: n = 6.

Figure 2  Representative illustrations of changes in MABP and HR after application of the air jet stressor (arrow) in the sham-operated and infarcted rats during ICV infusion of 0.9% NaCl, OXY or OXYANT. The Figure shows that (1) during infusion of 0.9% NaCl MABP and HR responses to stress are markedly greater in the infarcted than in the sham-operated rat, (2) ICV administration of OXYANT intensifies MABP and HR responses to stress in the sham-operated but not in the infarcted rat and (3) ICV administered OXY reduces MABP and HR responses to stress in the infarcted but not in the sham-operated rat.

Figure 3  Mean maximal changes of MABP and HR from baseline after application of air jet stress in the sham-operated (open columns) and infarcted (filled columns) rats receiving ICV infusions of 0.9% NaCl, OXY or OXYANT. Number of rats per group: sham-operated 0.9%: n = 7; sham-operated OXY: n = 6; sham-operated OXYANT: n = 7; infarcted 0.9% NaCl: n = 8; infarcted OXY: n = 6; infarcted OXYANT: n = 6. Asterisks indicate significant differences between the experimental groups *P < 0.05; **P < 0.01; ***P < 0.001.