Antidepressant-like effect of different estrogenic compounds in the forced swimming test

Antidepressant effects of ERβ-selective estrogen receptor modulators in the forced swim test

Estradiol (E2) may influence depressive symptomology of women and decrease depressive behavior among rodents. The mechanism(s) for E2's antidepressant effects are not well understood. To determine whether antidepressant effects of E2 may involve actions at intracellular estrogen receptor (ER) alpha or beta isoforms, selective ER modulators (SERMs) were administered (10 microg sc) to ovariectomized rats 48 h before testing in the forced swim test, an animal model of depression, and the horizontal crossing task. Rats received sesame oil vehicle, 17beta-E2, which has a high affinity for ERalpha and ERbeta, SERMs that vary in their activity at ERalpha and beta, or a tricyclic antidepressant (desipramine; 30 mg/kg ip), as a positive control. ERalpha-selective SERMs were propyl pyrazole triol (PPT) and 17alpha-E2. PPT has more selective effects at ERalpha than does 17alpha-E2, which also binds ERbeta. ERbeta-selective SERMs were diarylpropionitrile (DPN) and 7,12-dihydrocoumestan (coumestrol). DPN is more selective at ERbeta than coumestrol, which also binds ERalpha. 17beta-E2, ERbeta-selective SERMs (DPN, coumestrol), and desipramine administration produced antidepressive behavior (decreased immobility, increased struggling and swimming). ERalpha-selective SERMs (PPT, 17alpha-E2) were not different from vehicle. There were no differences among groups in the number of beam breaks made in the horizontal crossing task. These data suggest that E2's antidepressive effects may involve actions at ERbeta.

Estrogens and non-reproductive behaviors related to activity and fear

Estrogens affect a variety of behaviors in addition to sexual responses, some of them related to motor activity and emotional reactivity. This is true in experimental animals and in humans. The literatures on these subjects are confusing because not all of the experimental results point in the same direction. Here we propose the following theoretical suggestion, hoping to account for the variety of reports extant: following the generally arousing effects of estrogens, their hormonal actions on motor activity and fear depend on context. In a safe environment, estrogen treatment causes increased activity. But in a novel environment or in contexts otherwise perceived as threatening, activity is reduced by estrogen, due to the hormone's arousing action, which heightens fear. Many hormone-dependent neural circuits involving several neuropeptides could provide mechanisms for this dynamic. We suggest a causal route could involve the activation of corticotropin releasing hormone gene expression in the brain. In sum, estrogenic effects on arousal states, as manifest differently according to details of the environmental context during behavioral test, could account for some of the discrepancies in the literature.

Aphrodisiac properties of Montanoa tomentosa aqueous crude extract in male rats

Cihuapatli, the Mexican zoapatle (Montanoa tomentosa) has an extensive ethnomedical history of use as a traditional remedy for reproductive impairments. During the study of the ejaculatory function in rats and by testing a set of Mexican plants with medicinal properties, we observed that crude extracts of M. tomentosa facilitated ejaculation. Thus, we decided to analyze the possibility that this plant possessed sexual stimulant properties. To that aim, copulatory behavior of sexually active male rats receiving doses of 38, 75 and 150 mg/kg of the aqueous crude extract of M. tomentosa, as it is prepared in traditional medicine, was assessed. In addition, we evaluated the effect of the 75-mg/kg dose of the extract on males with anesthetization of the genital area and on sexual behavior of sexually inactive male rats (noncopulators). Results showed that acute oral administration of crude extracts of M. tomentosa facilitates expression of sexual behavior in sexually active male rats, significantly increases mounting behavior in genitally anesthetized animals and induces the expression of sexual behavior in noncopulating males. Altogether, these data reveal a facilitatory action of this extract on sexual activity and particularly on sexual arousal. Present findings provide experimental evidence that the crude extract preparation of M. tomentosa, used as a traditional remedy, possesses aphrodisiac properties.

Interaction between estrogens and antidepressants in the forced swimming test in rats

RATIONALE

Several reports suggest that estrogens possess antidepressant effects and could facilitate the action of some antidepressants.

OBJECTIVE

To analyze the interaction between three different types of estrogens, 17 beta-estradiol (E(2)), ethinylestradiol (EE(2)) or diethyl-stilbestrol (DES) and the antidepressants, fluoxetine (FLX) or desipramine (DMI) in ovariectomized female rats subjected to an animal model for the study of antidepressant compounds, the forced swimming test (FST).

METHODS

The effect of the combination of a sub-optimal dose of FLX (2.5 mg/kg) or DMI (2.5 mg/kg) with a sub-active dose of E(2 )(10 microg/kg), EE(2), (2.5 or 5 microg/kg) or DES (1 mg/kg) was analyzed in both the FST and the open field paradigm.

RESULTS

The combination of a sub-optimal dose of E(2) or DES with that of the antidepressant DMI resulted in a clear antidepressant-like effect, evidenced by a significant decrease in immobility accompanied by an increase in climbing behavior. Sub-optimal doses of either E(2) or DES also facilitated the antidepressant-like effect of a sub-optimal dose of FLX. In this case, a decrease in immobility with a concomitant increase in swimming behavior was observed. Finally, the combination of EE(2) with either DMI or FLX decreased immobility and induced an increase in both swimming and climbing behaviors. All combinations decreased rats' locomotor activity when evaluated in the open field test.

CONCLUSION

In the FST estrogens were able to facilitate the action of two different kinds of antidepressants; however, these effects were dependent on the type of estrogen used.