Anatomical differences in uterine sensitivity to prostaglandin F(2alpha) and serotonin in non-pregnant rats.

The ovarian steroids regulate the sensitivity of a population of uterine receptors to prostaglandin F(2alpha), serotonin and oxytocin. However, the uterine sensitivity to prostaglandin F(2alpha) and oxytocin does not coincide with the estrogen-induced increase in the number of receptors. Anatomical differences affect the uterine sensitivity to agonists. We investigated whether anatomical differences between ovarian and cervical uterine regions modulate the hormone-regulated sensitivity to prostaglandin F(2alpha), serotonin and oxytocin. Non-cumulative concentration-response curves for these agonists were recorded for ovarian and cervical uterine segments from adult ovariectomized rats treated with 17beta-estradiol, 17beta-estradiol+progesterone, or vehicle. The ovarian segments displayed a higher maximal response (E(max)) to prostaglandin F(2alpha) and a lower E(max) to serotonin than the cervical segments. Both uterine segments displayed a similar sensitivity to oxytocin. The ovariectomized controls displayed the highest E(max) and the lowest effective concentration 50 (EC(50)) for oxytocin and prostaglandin F(2alpha). Anatomical differences between ovarian and cervical uterine regions modulate the hormonal regulation of uterine sensitivity to serotonin and prostaglandin F(2alpha) in the non-pregnant rat uterus.

Antiestrogen U23,469 induced alterations of catecholamine levels on plasma and central nervous system

The effect of antiestrogen U23,469 administration in vivo on the centration of dopamine, norepinephrine and epinephrine in the plasma, cerebral cortex and hypothalamus in ovariectomized rats was investigated. Rats were treated with estradiol benzoate, progesterone and U23,469 in different doses, s.c., daily for 6 days. Control group was injected with sesame oil. Catecholamines were estimated by radioenzymatic assay. Six days of U23,469, estradiol benzoate, progesterone or its combination altered the catecholamine levels compared to the control. Dopamine decreased in plasma with progesterone and U23.469. In the cerebral cortex, progesterone and U23,469 increased significantly and in the hypothalamus all the treatments produced a decrease of catecholamines. The levels of NE were reduced with estradiol benzoate, progesterone and U23,469; there was no significant difference in the norepinephrine levels after different treatments in the cerebral cortex, but the NE levels were significantly decreased inthe hypothalamus. Epinephrine Showed differences related to the treatment, as in plasma, as in cerebral cortex and hypothalamus. These resultas suggest that antiestrogen treatment compared with the estradiol benzoate or progesterone may affect the catecholamine levels of the central nervous system and plasma and support the idea that AE could have an indirect effect on the catecholaminergic system

Liberación de noradrenalina intramural inducida por soluciones despolarizantes de potasio en utero de rata / Release of intramural noradrenaline induced by depolarizing solutions of potassium in rat uteri

Se estudió la correlación entre la actividad contractil y la liberación de noradrenalina por soluciones de cloruro de potasio (40, 60, 70, 80, 90 y 123mM) en preparaciones de útero de rata a través de las diferentes fases del ciclo estrul, como son el metaestru (M), diestro (D), proestro (P) y estro (E) y útero de rata ovariectomizada (DVX). La respuesta contractil del útero de rata al medio cargado de cloruro de potasio (KCL) depende del estadío endócrino en el que se encuentra. De este modo los úteros de ratas OVX y en las fases M,D,P y E muestran una contracción tóxica al sumergirse en el medio con 40 mM de KCL. Los úteros de ratas OVX y en las fases M y D mostraron una contracción inicial seguida por un relajamiento transitorio, al exponerse a concentraciones de 60, 70, 80, 90, y 123 mM de KCL. En el uretero de ratas en las fases de P y E se disminuyó importantemente el estadío de relajación transitoria al exponerse a soluciones de 60, 70, 80, 90 y 123mM de KCL, presentando solamente contracciones tóxicas. Tiras uterinas de ratas OVX se relajaron significativamente más por KCL de 123 mM que las tiras uterinas en fase de P (0'001). El agregado de propanolol (2D mM) a las tiras uterinas de ratas OVX inhibió la relajación transitoria observada con 123 mM de KCL. 40 mM de KCL no afectaron el eflujo de noradrenalina marcada con tritio (3H-NA) en tiras uterinas de ratas OVX cargadas previamente con transmisor radioactivo. En estas condiciones, se observó que 123 mM de KCL aumentaban el eflujo de 3H-NA. El propanolol (20mM) no afectó la liberación de 3H-NA producida por KCL (123mM) en tiras uterinas de ratas OVX. El estudio presente muestra que los cambios en la contractilidad uterina ante estímulos quirúrgicos durante las diferentes fases del ciclo estral y en ratas OVX podría deberse a la acción de esteroides sexuales a nivel presinóptico al modular la liberación de neurotransmisores