Laboratorio Of Farmacologia Conductual
Laboratorio Of Farmacologia Conductual
Ramos M.F.,Instituto Nacional Of Perinatologia Isidro Espinosa Of Los Reyes |
Mota L.M.,Instituto Nacional Of Perinatologia Isidro Espinosa Of Los Reyes |
Mota L.M.,Laboratorio Of Farmacologia Conductual
Salud Mental | Year: 2012
Depression is an affective disorder that is more frequent in women than men. The etiology of depression disorders is multi-factorial, since social and biological influences have been determined. Coincidence between periods with hormonal fluctuations and affective alterations has lead to a hypothesis that considers fluctuations in gonadal hormones as a possible cause of depression in women. In this respect, pre-clinical studies by using laboratory animals (rodents) point toward a stronger relationship between hormonal oscillations and depressive behavior in different models designed to evaluate the antidepressant effect of drugs. This evidence could be interesting since in pre-clinical studies social factors are not included. Specifically, several authors have reported that depressive behavior is more prevalent in stages of rats' life characterized by low concentrations of gonadal hormones, such as postpartum, diestrous phase, lactancy and after ovariectomy. In contrast, a major presence of depressive behavior is observed in phases with higher concentration of hormones, like proestrus (a phase coincident with ovulation), pregnancy and after hormonal restitution with estrogens and progestins. Interestingly, the development of depressive behavior after ovariectomy has been established in female mice, with a critical period 12 weeks after ovaries extirpation. The participation of specific hormones in female depression could be studied in lab animals, since rodent female progress from a reproductive to a non-reproductive phase with vaginal and endocrine changes. Young females have a 4-5 days cycle named estrous cycle, in which each vaginal phase is associated with different concentrations of gonadal hormones. Although rodents do not exhibit menses, a state similar to peri- and post-menopause could be identified. Aging females exhibit irregular cycles before progressing to an estrous constant phase with elevated levels of estrogens. Decline of estrogen levels produces a persistent diestrous phase considered as a postmenopausal state. Aging rats in persistent diestrous, as well as ovariectomized females (the most economic model of post-menopause in lab animals) show physiological and behavioral changes associated to hormonal deprivation. Thus, they are considered a good model to evaluate affective and cognitive alterations as well as potential hormonal substitutive treatments. Clinical and epidemiologic studies report that perimenopause is linked to an increased risk of developing depression in women, or with the presence of more intense symptoms of depression. In agreement with Stages of Reproductive Aging Workshop (STRAW), perimenopause includes the period named transition to menopause plus one year after the last menses. This period is characterized by irregular menstrual cycles and fluctuations in levels of estrogens. In this stage, the levels of follicle-stimulating hormone (FSH) are elevated in order to further stimulate the production of estrogens from ovaries. Finally, concentrations of estrogens are significantly reduced in late perimenopause, although the levels of FSH continue to be increased. Fluctuations of estrogens and FSH have been related to symptoms such as affective alterations, hot flushes and insomnia, while hormonal deprivation in post-menopause is linked to changes in body fat, fatigue, cognitive disorders and reduction in bone density. Variations in estrogens and FSH level have been consistently related to depression symptoms in perimenopausal women, while changes in progestins and testosterone are associated with dysphoric mood and aggression, respectively. Thus, in agreement with the main hormonal hypothesis, a substitutive therapy with estrogens as an antidepressant therapy in peri- and post-menopausal women has been implemented. The results of different clinical studies are contradictory possibly due to methodological differences as the type of hormone used as an antidepressant therapy, dosage, time of administration of treatments and the period of hormonal deprivation in women. In a consistent manner, basic studies support the idea that steroidal gonadal hormones have antidepressant properties, but these seem to depend on both specific features of hormonal treatments and endocrine conditions in females. It has been reported that 17β-estradiol (E 2), ethinyl-estradiol (EE 2) and estradiol benzoate produce antidepressant-like actions in ovariectomized young females. Pharmacological studies have demonstrated that the serotonergic system has a major participation in the antidepressant-like effect of E 2, revealing its potential as a treatment for depressed women. In the same sense, estrogens that bind to estrogen receptors β (ERβ) are more effective to produce antidepressant- and anxiolytic-like effects than estrogens with higher affinity at ERα This evidence leads to consider ERβ as an important pharmacological target in depression. Studies evaluating estrogens in depression have determined that dosage is an important issue in the production of antidepressant-like effects. Dosage of estrogens that attain a physiological range have been reported to have more antidepressant efficacy in respect to lower or higher dose provoking infra- or supra-physiological levels of estradiol. In fact, a U-shape in the antidepressant effect of E 2 has been detected. Finally, timing of hormonal therapy seems to be a more relevant factor at moment to attain an antidepressant effect with estrogen treatment. Old rats (14 months) that received a prolonged estrogen treatment immediately after ovariectomy showed an antidepressant-like response which was not observed when treatment was began five months after ovaries extirpation. ERs are dependent on endogenous estrogens levels which suggest that a reduction in the target site of E 2 may be linked to its reduced antidepressant-like effect in females with a long-term hormonal deprivation. An apparently successful strategy to reduce depression in women has been to adjunct a hormonal treatment with antidepressant drugs in order to enhance antidepressant efficacy. Studies with a reduced number of patients have determined that combined therapy is able to reduce the scores in the Hamilton Depression Scale, and to allow the effect of antidepressant drugs in women with refractory depression. At this respect, basic studies have established that estrogens facilitate the antidepressant effects of several antidepressant drugs. It was reported that the anxiolytic effect of desipramine was more evident in the proestrus, a phase characterized by high levels of estrogens and progesterone in young females. Both estrogens and progesterone participate in the anxiolytic effect of desipramine, although the synergism with estradiol was more significant. By using specific animal models of antidepressant effects, it was found that E 2 facilitated the antidepressant effect of fluoxetine, desipramine, venlafaxine and bupropion in young, ovariectomized female rodents. In contrast, a chronic study using old, ovariectomized female rats showed that estradiol valerate was unable to improve the antidepressant effect of citalopram, even though the antidepressant efficacy of both estrogen and citalopram was established previously. Differences in results could be due to variations in methodological aspects such as age of rats (young, three months, versus old, 15 month), type of estrogen used in each study (E 2 versus estradiol valerate), animal model of depression (forced swimming test, acute model, versus chronic mild stress model), type of antidepressant used (citalopram in the last case), and dosage for both estrogens and antidepressant drugs. Interestingly, the strategy of a combined treatment could be a therapeutic advantage for those women that suffer depression associated to endocrine changes. Evidence from clinical and basic studies should be taken into account at moment to select the most advantageous therapy to treat depression in mature women.
PubMed | Laboratorio Of Farmacologia Conductual
Type: Journal Article | Journal: Hormones and behavior | Year: 2012
Middle-aged male rats are more vulnerable than young adult ones to develop anhedonia when exposed to chronic mild stress (CMS). Clinical studies support the idea that in aged subjects the low testosterone (T) levels are related with their higher stress vulnerability and that this hormone possesses antidepressant-like actions. In this study we evaluated the role of gonadal hormones--mainly T--on the depressive-like behavior of middle-aged and young adult male rats submitted to CMS. In middle-aged rats we analyzed the effect of T restitution (at the levels of young adult animals) given 3 weeks before (experiment 1) or 3 weeks after (experiment 2) anhedonia development (indicated by a reduction in sucrose solution intake). T restitution before CMS effectively prevented anhedonia but failed to reverse it once installed. In young adult rats we studied if orchidectomy increased stress vulnerability and found that it failed to modify sucrose intake. These results indicate a stress-dependent differential effect of T in middle-aged rats an age differential role of gonadal hormones on the vulnerability to develop anhedonia. The results suggest that T is a resilience factor in middle-aged but not in young adult males.