Chronic effect of antidopaminergic drugs or estrogen on male Wistar rat lactotrophs and somatotrophs

The aim of the present study was to evaluate the effect of antidopaminergic agents on the somatotrophs in the presence of hyperprolactinemia. Adult male Wistar rats were divided into 6 groups: a control group and five groups chronically treated (60 days) with haloperidol, fluphenazine, sulpiride, metoclopramide or estrogen. Somatotrophs and lactotrophs were identified by immunohistochemistry and the data are reported as percent of total anterior pituitary cells counted. The drugs significantly increased the percentage of lactotrophs: control (mean ± SD) 21.3 ± 4.4, haloperidol 27.8 ± 2.2, fluphenazine 34.5 ± 3.6, sulpiride 32.7 ± 3.5, metoclopramide 33.4 ± 5.5 and estrogen 42.4 ± 2.8. A significant reduction in somatotrophs was observed in animals treated with haloperidol (23.1 ± 3.0), fluphenazine (22.1 ± 1.1) and metoclopramide (24.2 ± 3.0) compared to control (27.3 ± 3.8), whereas no difference was observed in the groups treated with sulpiride (25.0 ± 2.2) and estrogen (27.1 ± 2.8). In the groups in which a reduction occurred, this may have simply been due to dilution, secondary to lactotroph hyperplasia. In view of the duplication of the percentage of prolactin-secreting cells, when estrogen was applied, the absence of a reduction in the percent of somatotrophs suggests a replication effect on this cell population. These data provide additional information about the direct or indirect effect of drugs which, in addition to interfering with the dopaminergic system, may act on other pituitary cells as well as on the lactotrophs.

Dopaminergic modulation of grooming behavior in virgin and pregnant rats

Dopamine receptors are involved in the expression of grooming behavior. The pregnancy-induced increase in self-licking observed in rats is important for mammary gland development and lactation. This study focuses on the role of dopamine receptor subtypes in grooming behavior of virgin and pregnant female rats. General and mammary gland grooming were measured in virgin rats treated with 0.25 mg/kg of the D1-like agonist SKF-81297 and antagonist SKF-83566 and the D2-like agonist lisuride and antagonist sulpiride. The effects of 0.01 and 0.25 mg/kg doses of the same agonists and antagonists were evaluated in pregnant rats as well. In virgin animals both SKF-83566 and sulpiride treatments significantly reduced the time spent in general grooming, while none of the dopamine agonists was able to significantly change any parameter of general grooming. Time spent in grooming directed at the mammary glands was not affected significantly by any of the drug treatments in virgin rats. All drugs tested significantly decreased the frequency of and the time spent with general grooming, while SKF-81297 treatment alone did not significantly reduce the duration of mammary gland grooming in pregnant rats. These data show that in female rats the behavioral effects of D1-like and D2-like dopamine receptor stimulation and blockade differ according to physiological state. The results suggest that dopamine receptors may play specific roles modulating grooming behavior in pregnant rats. Since grooming of the mammary gland during pregnancy may influence lactation, this aspect is relevant for studies regarding the perinatal use of dopamine-related drugs.

Antidepressant-like effect of Hoodia gordonii in a forced swimming test in mice: evidence for involvement of the monoaminergic system

Hoodia gordonii is a plant species used traditionally in southern Africa to suppress appetite. Recently, it has been associated with a significant increase in blood pressure and pulse rate in women, suggesting sympathomimetic activity. The present study investigated the possible antidepressant-like effects of acute and repeated (15 days) administration of H. gordonii extract (25 and 50 mg/kg, po) to mice exposed to a forced swimming test (FST). Neurochemical analysis of brain monoamines was also carried out to determine the involvement of the monoaminergic system on these effects. Acute administration of H. gordonii decreased the immobility of mice in the FST without accompanying changes in general activity in the open-field test during acute treatment, suggesting an antidepressant-like effect. The anti-immobility effect of H. gordonii was prevented by pretreatment of mice with PCPA [an inhibitor of serotonin (5-HT) synthesis], NAN-190 (a 5-HT1A antagonist), ritanserin (a 5-HT2A/2C antagonist), ondansetron (a 5-HT3A antagonist), prazosin (an α1-adrenoceptor antagonist), SCH23390 (a D1 receptor antagonist), yohimbine (an α2-adrenoceptor antagonist), and sulpiride (a D2 receptor antagonist). A significant increase in 5-HT levels in the striatum was detected after acute administration, while 5-HT, norepinephrine and dopamine were significantly elevated after chronic treatment. Results indicated that H. gordonii possesses antidepressant-like activity in the FST by altering the dopaminergic, serotonergic, and noradrenergic systems.