Estrus variation in anticonflict-like effects of the mGlu5 receptor antagonist MTEP, microinjected into lateral septal nuclei of female Wistar rats.

Anticonflict-like effects of the mGlu5 receptor antagonist MTEP (systemic administrations: 1.50, 3.0 or 6.0 mg/kg; i.p.; intra-lateral septal nuclei or intra-medial septal region infusions: 2.5 microg/microl, 5.0 microg/microl or 10.0 microg/microl) were assessed in Wistar rats during late proestrus or metestrus-diestrus. Results showed that control rats displayed an increased number of immediately punished reinforcers during late proestrus (P < 0.05), when compared to metestrus-diestrus. During late proestrus, systemic administrations (3.0 mg/kg, P < 0.05; 6.0 mg/kg P < 0.05) or intra-lateral septal nuclei infusions (5.0 microg/microl, P < 0.05; 10.0 microg/microl, P < 0.05) of MTEP increased the number of immediately punished reinforcers received. During metestrus-diestrus only the highest doses of MTEP (systemic administration: 6.0 mg/kg P < 0.05; intra-lateral septal nuclei infusions: 10.0 microg/microl, P < 0.05) increased the number of immediately punished reinforcers obtained. MTEP infusions into the medial septum produced neither of these anticonflict effects. In conclusion, data showed an estrus variation in those anticonflict-like effects of the mGlu5 receptor antagonist MTEP, systemically administered or microinjected into lateral septal nuclei of female Wistar rats.

Antidepressant-like actions of intra-accumbens infusions of allopregnanolone in ovariectomized Wistar rats.

This study was aimed to verify the role of the nucleus accumbens (NAcc) in the antidepressant-like effects of allopregnanolone in ovariectomized rats forced to swim. The interaction between infusions of allopregnanolone (intra-NAcc) with systemic administrations of allopregnanolone, muscimol, fluoxetine and GABA-A antagonists was assessed. Results showed that allopregnanolone (intra-NAcc; 1.5 microg, p < 0.05; 2.0 microg, p < 0.05) or systemic injections of allopregnanolone (1.5 mg/kg, p < 0.05; 2.0 mg/kg, p < 0.05; s.c.) or muscimol (0.3 mg/kg, p < 0.05; 0.6 mg/kg, p < 0.05; i.p.) reduced immobility by increasing climbing in the forced swimming task (FST), whereas fluoxetine (1.0 mg/kg, p < 0.05; 2.0 mg/kg, p < 0.05; i.p.) reduced immobility by increasing swimming. Allopregnanolone (intra-NAcc; 0.5 microg/side) synergized with systemic doses of allopregnanolone (0.5 mg/kg; p < 0.05), muscimol (0.1 mg/kg; p < 0.05) or fluoxetine (0.5 mg/kg; p < 0.05) and reduced immobility by increasing climbing. Picrotoxin (0.125 mg/kg; i.p.) attenuated the synergism of the combination allopregnanolone (intra-NAcc; 0.5 microg/side) plus fluoxetine (i.p.) or allopregnanolone (s.c.) and the effects of allopregnanolone (intra-NAcc; 1.5 microg/side). Bicuculline (2.0 mg/kg; i.p.) attenuated the synergism between the combination allopregnanolone (intra-NAcc; 0.5 microg/side) plus muscimol (i.p.), but not the synergism of the combination allopregnanolone (intra-NAcc; 0.5 microg/side) plus allopregnanolone (s.c.). In conclusion, allopregnanolone (systemic injections or intra-NAcc), fluoxetine or muscimol produced antidepressant-like effects in the FST. Subthreshold doses of allopregnanolone (intra-NAcc) synergized with systemic subthreshold doses of fluoxetine, muscimol or allopregnanolone. Antagonists of the GABA-A receptor canceled the synergism.

Anticonflict actions of aqueous extracts of flowers of Achillea millefolium L. vary according to the estrous cycle phases in Wistar rats.

Anticonflict-like effects of aqueous extract of flowers of Achillea millefolium L., a plant with purported anxiolytic actions, were studied in female Wistar rats during late proestrus or diestrus. During late proestrus (p < 0.05), control rats displayed reduced conflict behavior compared with diestrus. Diazepam (2.0 mg/kg; i.p.) reduced conflict behavior both during late proestrus (p < 0.05) or diestrus (p < 0.05). Doses of 8.0 mg/kg (p < 0.05), 10.0 mg/kg (p < 0.05) or 12.0 mg/kg (p < 0.05) of Achillea millefolium reduced conflict behavior during late proestrus. Conversely, during diestrus, only the dose of 12.0 mg/kg (p < 0.05) of Achillea millefolium L. reduced conflict behavior. In conclusion, the anticonflict-like actions of Achillea millefolium L. may vary according to the estrous cycle phase.

Anxiolytic-like actions of leaves of Casimiroa edulis (Rutaceae) in male Wistar rats.

Anxiolytic-like actions of an aqueous extract of the leaves of Casimiroa edulis (Ce) La Llave ex Lex. (Rutaceae) were studied in male Wistar rats in the elevated plus-maze test, whether effect on locomotion were studied in the open-field task, and its possible antidepressant-like actions in the forced swimming task. In the elevated plus-maze test, diazepam (Dz) (1.30 mg/kg; P < 0.05) and Casimiroa edulis (25.0 mg/kg, P < 0.05; 35.0 mg/kg, P < 0.05) increased open arms exploration (i.e., anxiolytic-like action). Doses of 45.0 mg/kg (P < 0.05) and 55.0 mg/kg (P < 0.05) of Casimiroa edulis reduced locomotion in the elevated plus-maze test and in the open-field test. In the forced swimming task, desipramine (dmi) (32.0 mg/kg; P < 0.05) reduced immobility (i.e., antidepressant-like action). Conversely, as compared to control rats, neither diazepam (Dz) (1.30 mg/kg) nor Casimiroa edulis (25.0 mg/kg) modified immobility in the forced swimming task. However, diazepam (P < 0.05) or Casimiroa edulis (P < 0.05), when co-administered, canceled the antiimmobility actions of desipramine. In conclusion, the leaves of Casimiroa edulis (Rutaceae) produced anxiolytic-like actions in male Wistar rats, with several side actions, namely, reduced locomotion and neutralization of the antidepressant-like actions of desipramine.

Anti-conflict-like actions of intralateral septal infusions of allopregnanolone in Wistar rats.

The aim of the present study was to test the hypothesis that allopregnanolone infused into the lateral septal nuclei will reduce conflict-like behavior in ovariectomized rats. The interaction with systemic administration of several agonists and antagonists of the GABA-A receptor was assessed. Results showed that intralateral septal doses of allopregnanolone (1.0 microg, P<.05; 2.0 microg, P<.05) or systemic injections of allopregnanolone (1.0 mg/kg s.c., P<.05; 2.0 mg/kg s.c., P<.05), diazepam (2.0 mg/kg i.p., P<.05), or muscimol (0.3 mg/kg i.p., P<.05; 0.6 mg/kg i.p., P<.05) reduced conflict-like behavior. Subthreshold doses of intralateral septal infusions of allopregnanolone (0.5 microg/side) synergized with systemic subthreshold doses of GABA-A agonists: allopregnanolone (0.5 mg/kg, P<.05), diazepam (1.5 mg/kg, P<.05), or muscimol (0.1 mg/kg, P<.05). The GABA-A antagonists, flumazenil (0.1 mg/kg i.p.) and bicuculline (2.0 mg/kg i.p.) attenuated the synergism between intralateral septal infusions of allopregnanolone and diazepam or muscimol, respectively. Conversely, neither flumazenil (P<.05) nor bicuculline (P<.05) attenuated the synergism of the combination allopregnanolone (intralateral septum nuclei; 0.5 microg/side) plus systemic injections of allopregnanolone. In conclusion, allopregnanolone reduced conflict-like behavior probably acting at the GABA-A receptors found in the lateral septal nuclei.

Antidepressant-like actions of pregnancy, and progesterone in Wistar rats forced to swim.

In rats, some behavioral changes occurring during pregnancy related to the presence of progesterone may be analyzed in the forced swimming task (FST), which is designed to test the antidepressant profile of drugs. The present study was aimed to analyze in pregnant rats, in rats after delivery, or in rats after receiving progesterone those behavioral changes displayed in the FST. We hypothesize that pregnancy and progesterone will produce antidepressant-like effects in rats forced to swim. Therefore, pregnant rats (14th, 17th, and 20th days), or rats after delivery (3rd, and 7th days) were tested in the FST. Ovariectomized rats receiving saline (0.9%; i.p.), clomipramine (1.25 mg/kg; i.p.), or desipramine (2.14 mg/kg; i.p.) for 28 days were also tested in the FST. In a second series of experiments, ovariectomized rats receiving vehicle or progesterone (0.5 mg/kg; or 2.0 mg/kg; sc.) were tested in the FST. Locomotion was evaluated in the open field test. Results showed that in the FST: 1) pregnancy (P < 0.05), or progesterone (P < 0.05), or desipramine (P < 0.05), reduced immobility by increasing climbing; 2) clomipramine (P < 0.05) reduced immobility by increasing swimming; 3) rats tested after delivery displayed similar behavior than control rats. A lower locomotion was observed only at the end of pregnancy. In conclusion, results suggest that during pregnancy, a reproductive process characterized by its high levels of progesterone, antidepressant-like effects can be found.

Estrus variation in anticonflict effects of midazolam microinjected into septal nuclei in female Wistar rats.

Effects of midazolam intraperitoneally (3.0 mg/kg) administered, or locally applied into lateral septal nuclei (10 microg/microl), or into the medial septum (10 microg/microl) were assessed in Wistar rats during late proestrus or metestrus-diestrus in a conflict-operant task. A reduction in conflict behavior was found in control rats during late proestrus (P<.05), when compared to metestrus-diestrus. Systemic injections of midazolam (P<.05) or midazolam infusions into lateral septal nuclei (P<.05) also reduced conflict behavior only during late proestrus, whereas midazolam infusions into the medial septum produced neither of these anticonflict effects in any estrous phase. In conclusion, an endocrine-related variation in anticonflict effects of midazolam microinjected into lateral septal nuclei was displayed by female rats.