Proceedings of The Physiological Society
University of Bristol (2005) J Physiol 567P, PC57
Effect of acute stress in the day of proestrus on sexual behaviour and ovulation in female rats: participation of angiotensinergic system
Donadio, Marcio Vinicius Fagundes; Kunrath, Aline; Anselmo-Franci, Janete A.; Franci, Celso Rodrigues; Lucion, Aldo Bolten; Sanvitto, Gilberto Luiz;
1. Departamento de Fisiologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. 2. Departamento de Fisiologia, Faculdade de Odontologia de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, SP, Brazil. 3. Departamento de Fisiologia, Faculdade de Medicina de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, SP, Brazil.
Physical or emotional stress can affect reproductive function. Angiotensin II (AII) is a hormone that participates in the stress response and also in the control of reproductive hormones. The study aimed to evaluate the effects of acute stress in the morning and afternoon of proestrus on the sexual behaviour and ovulation in female rats and also the participation of AII on the stress-induced effects. Adult female Wistar rats (n=193) had the oestrous cycle monitored daily. Rats with three regular cycles were used. We tested different paradigms of stress in the morning (10h) and in the afternoon (16h) of proestrus: control (no intervention) (n=17/n=17); restraint stress 10min (n=13/n=17); restraint stress 1h (n=15/n=15) and ether stress (n=14/n=13), respectively. We analysed sexual behaviour and ovulation. We also tested the participation of AII on the effects of stress (restraint 1h) in the morning of proestrus by injecting AII receptor antagonists: peripheral (i.p.) injection (control, n=10; saline + stress, n=8; losartan + stress, n=7; PD + stress, n=7; losartan/PD + stress, n=8) and central (i.c.v.) injection (control, n=8; stress, n=8; saline + stress, n=8; losartan + stress, n=8). We analysed ovulation. For central injection an i.c.v. guide cannulae was stereotactically implanted under ketamine/xylasine anaesthesia (100/50 mg/kg, i.m.). Peripheral (saline, 0.9%, losartan (AT1 antagonist), 10mg/kg and PD123319 (AT2 antagonist), 3mg/kg) and central (saline, 0.9% and losartan, 5μg/2μl) injections were performed 15min before stress. Number of lordosis/mounts (lordosis quotient) was recorded for 15min. The number of oocytes was counted in the morning of oestrous. All animals were humanely killed at the end of the experiments. All data (mean±S.E.M.) were compared by one-way ANOVA followed by Newman-Keuls test. Stress in the morning of proestrus induced a reduction in the number of oocytes in all stress groups when compared with control group: control (11.7±0.6), 10min restraint (7.5±0.7), 1h restraint (7.7±0.5) and ether (8.7±0.8) (p<0.05). No difference was found in the lordosis quotient. Stress in the afternoon of proestrus induced a reduction in the lordosis quotient when 1h restraint (0.81±0.05) was compared with control (0.96±0.01) (p<0.05). We found no difference in the number of oocytes in this experiment. Peripheral losartan (10.5±0.7) and losartan + PD (11±0.3) partially reverted the stress-induced effects on ovulation when compared with control (12.6±0.5) and saline (6.4±0.6) (p<0.05). PD (6.6±0.5) injected alone had no effect. Central losartan (8.5±0.8) also partially reverted the stress-induced effects on ovulation when compared with control (11.6±0.5) and saline (6.0±0.8) (p<0.05). The results indicate that acute stress in the morning of proestrus alters mechanisms that control ovulation, as shown by the reduction in the number of oocytes, while stress in the afternoon alters mechanisms that control sexual behaviour. The stress-induced reduction in the ovulation is mediated, at least in part, by the angiotensinergic system through AT1 receptors.
Where applicable, experiments conform with Society ethical requirements