Lepidium meyenii (Maca) does not exert direct androgenic activities.

Maca is the edible root of the Peruvian plant Lepidum meyenii, traditionally employed for its purported aphrodisiac and fertility-enhancing properties. This study aimed at testing the hypothesis that Maca contains testosterone-like compounds, able to bind the human androgen receptor and promote transcription pathways regulated by steroid hormone signaling. Maca extracts (obtained with different solvents: methanol, ethanol, hexane and chloroform) are not able to regulate GRE (glucocorticoid response element) activation. Further experiments are needed to assess which compound, of the several Maca's components, is responsible of the observed in vivo effects.

5Alpha-reductase type 2 and androgen receptor expression in gonadotropin releasing hormone GT1-1 cells.

Gonadal steroids are potent modulators of gonadotropin releasing hormone (GnRH) secretion, and androgen binding sites and 5alpha-reductase activity have been found in the immortalized GnRH secreting cell line GT1-1, suggesting the existence of a direct androgenic control of GnRH dynamics. Two isoforms of the 5alpha-reductase have been cloned with very different biochemical/functional properties: 5alpha-reductase type 1 (widely distributed in the body) and 5alpha-reductase type 2 (confined in androgen target structures). We have analysed whether, in GT1-1, androgen binding sites are linked to "classical" androgen receptor, and which 5alpha-reductase isoform is active. Reverse transcriptase-polymerase chain reaction analysis showed that the mRNAs coding for androgen receptor and for the two 5alpha-reductase isoforms are all expressed in GT1-1 cells. However, the 5alpha-reductase enzymatic reaction showed a peak of activity at a narrow pH around 5.5, the optimum for the 5alpha-reductase type 2. The affinity for testosterone, of the enzyme present in GT1-1 cells, was very similar to that observed for the recombinant type 2 isozyme expressed in yeasts. The data indicate that GT1-1 cells (i) express a "classical" androgen receptor and (ii) contain the 5alpha-reductase type 2 isoform, a specific marker of androgen-responsiveness.

Transient expression of the 5alpha-reductase type 2 isozyme in the rat brain in late fetal and early postnatal life.

The enzyme 5alpha-reductase plays a key role on several brain functions controlling the formation of anxiolytic/anesthetic steroids derived from progesterone and deoxycorticosterone, the conversion of testosterone to dihydrotestosterone, and the removal of excess of potentially neurotoxic steroids. Two 5alpha-reductase isoforms have been cloned: 5alpha-reductase type 1 is widely distributed in the body, and 5alpha-reductase type 2 is confined to androgen-dependent structures. In this study, the gene expression of the two 5alpha-reductase isozymes has been analyzed in fetal, postnatal, and adult rat brains by RT-PCR followed by Southern analysis. 5Alpha-reductase type 1 messenger RNA is always detectable in the rat brain [from gestational day 14 (GD14) to adulthood]. 5Alpha-reductase type 2 messenger RNA expression is undetectable on GD14, increases after GD18, peaks on postnatal day 2, then decreases gradually, becoming low in adulthood. This pattern of expression appears to be correlated with the rate of production of testosterone by the testis. The possible control by androgens of gene expression of the two isozymes has been studied in brain tissues of animals exposed in utero to the androgen antagonist flutamide; the sex of the animals was determined by genetic sex screening of the SRY gene located on the Y-chromosome. In the brain of male embryos, flutamide treatment inhibited the expression of 5alpha-reductase type 2; this effect was much less pronounced in females. Moreover, 5alpha-reductase type 2 gene expression in cultured hypothalamic neurons is highly induced by testosterone and by the phorbol ester 12-O-tetradecanoyl-phorbol-13 acetate. The transient, androgen-regulated, expression of 5alpha-reductase type 2 overlaps the critical period of development, which may be important for sexual differentiation of the brain and for the formation of anxiolytic/anesthetic steroids involved in the stress responses associated with parturition.

[Study of visual evoked potentials using a half-field pattern reversal under acupuncture in homonymous lateral hemianopsia]. / Etude des potentiels évoqués visuels par renversement de Pattern en hémichamp sous acupuncture au cours d'hémianopsies latérales homonymes.

The visual evoked potentials by half-field pattern reversal method were recorded in 12 hemianopic patients. The VEP amplitudes ipsilaterally to the occipital lesion were more important after periorbital acupuncture.

Ontogenetic development of the 5 alpha-reductase in the rat brain: cerebral cortex, hypothalamus, purified myelin and isolated oligodendrocytes.

In the central nervous system of the rat, the 5 alpha-reductase, the enzyme which converts testosterone into dihydrotestosterone, appears to be concentrated in the white matter and in particular to be associated with myelin. In order to verify whether a temporal correlation might exist between the formation of myelin membranes and the variations of the 5 alpha-reductase activity observed in the brain, the enzymatic activity was studied in the cerebral cortex and in the hypothalamus of male rat in the age range of 3-60 days, in myelin purified from animals of 15-60 days of life and in oligodendrocytes (i.e. in the cells responsible for the formation of the myelin) isolated from the brain of adult and very young rats (7th day of life, when the myelination process is not yet initiated). The results show that the formation of 5 alpha-androstane-17 beta-ol-3-one (DHT) in the cerebral cortex and in the hypothalamus has a peak activity in the first two weeks of life, before the beginning of the myelination process; purified myelin has an enzymatic activity always much higher than that present in the cerebral cortex and in the hypothalamus and shows a peak in the formation of DHT in the first period of myelinogenesis, on the third week of life. Finally the oligodendrocytes of young rats possess a much higher ability to convert testosterone into the 5 alpha-reduced metabolites than the oligodendrocytes of adult animals. A possible involvement of this enzyme in the myelin function may be hypothesized.

The 5 alpha-reductase activity of the subcortical white matter, the cerebral cortex, and the hypothalamus of the rat and of the mouse: possible sex differences and effect of castration.

Previous studies have shown that the central nervous system is able to convert testosterone into 17-beta-hydroxy-5-alpha-androstan-3-one (DHT), by the action of the enzyme 5-alpha-reductase. The data here presented show that, in the brain of the rat and the mouse of both sexes, the 5-alpha-reductase activity is more concentrated in the subcortical white matter than in the hypothalamus and in the cerebral cortex. The enzymatic activity is apparently higher in the rat than in the mouse brain. The formation of DHT in the subcortical white matter, in the hypothalamus and in the cerebral cortex of both rats and mice does not show any sexual difference. Moreover, in the rat no effect of short- or long-term castration or neonatal castration or testosterone replacement could be observed on the formation of DHT in the three brain structures considered (even in the subcortical white matter, the cerebral tissue more active in converting testosterone into DHT). The present data support the view that the 5-alpha-reductase present in the brain is not under androgenic control.