In the present study dehydroepiandrosterone (DHEA), androstenedione (A), testosterone (T) and dihydrotestosterone (DHT) plasma levels were determined in adult male rats five days, seven weeks and eleven weeks after orchiectomy and confronted, respectively, with rats 60 days old which were sacrificed 5 days, 7 weeks and 11 weeks after the sham-operation for orchiectomy. It was revealed that five days after castration A, T and DHT were decreased with respect to sham-operated rats. Seven and eleven weeks after orchiectomy only T remained lower. In all three groups of castrated animals the A/T ratio resulted augmented whereas T/DHT ratio resulted lower with respect to the sham-operated animals. Five days after castration DHEA plasma concentration was positively correlated to A levels and both androgens resulted negatively correlated to T plasma levels. Seven weeks after bilateral orchiectomy an inverse correlation appeared between DHEA/A ratio and T. This emphasizes the role of DHEA and A in maintaining testosterone circulating levels. Seven and eleven weeks following castration the A/T ratio was negatively related to the T/DHT ratio, indicating that A contributes to DHT plasma levels. In the second part of our study the effect of sex steroid administration was evaluated 7 weeks after castration. A linear correlation between DHEA and T circulating levels was obtained following the administration of T while treatment with oestradiol caused a significant increase of the DHEA/A ratio. The castrated animals that received DHT presented lower T circulating levels while the A/T ratio was significantly increased.(ABSTRACT TRUNCATED AT 250 WORDS)
The distribution of brain natriuretic peptide (BNP)-like immunoreactivity (ir) was studied in the brain of a urodele amphibian, the crested newt Triturus carnifex Laur. BNP-like immunoreactive neurons were found mainly in the caudal hypothalamus (retro- and supra-chiasmatic areas) and in the preoptic area. A widespread innervation throughout the brainstem as far as the spinal cord was also observed. By double immunostaining (after section incubation with a-BNP and a-tyrosine hydroxylase-TH-antibodies), close topographical relationships between BNP-like and TH-like immunoreactive neurons within the hypothalamus were found.
Labeling of the two more important gamma-aminobutyric acidA (GABA(A)) supramolecular sites with [3H] muscimol (GABA(A)) and [3H] flunitrazepam (benzodiazepine) provided saturable, stable, and dimorphic binding activities in cortical and limbic regions of the wood mouse Apodemus sylvaticus. Of the cortical layers, which contained the highest [3H] muscimol binding levels, only the female lamina V supplied a greater (51%; P <0.01) receptor density than in the male. Areas of the limbic system instead proved to be the more favorable targets for differential GABA(A) binding levels. The highest (P <0.001) and higher levels were found in the oriens-pyramidalis CA1 layer of the hippocampus (65%) and in the vertical limb diagonal band-medial septal nucleus (48%), basolateral amygdala nucleus (45%), and ventromedial hypothalamic nucleus (43%), respectively, of the female. A similar pattern was obtained for [3H]flunitrazepam binding activity, especially in the presence of GABA. The highest and higher binding activities were obtained in the female central amygdala nucleus (78%) and in the ventromedial hypothalamic nucleus (52%), basolateral amygdala nucleus (48%), and oriens-pyramidalis CA1 layer of the hippocampus (47%), respectively, whereas higher levels were observed only in the male vertical limb diagonal band-medial septal nucleus (56%). Even in the cortical regions, the female exhibited higher (42%; cortex lamina V) and moderately higher (38%; cortex lamina VI) levels, with binding differences in the latter site plus in the basolateral amygdala nucleus occurring in a GABA-nondependent manner. From the saturation binding analyses it was possible to reveal that both maximal number of binding sites (Bmax) and mean dissociation constant (K(D)) modifications were responsible for receptor differences of the two GABAergic sites. These findings tend to suggest that dimorphic variations of the GABA(A) supramolecular sites, in some cortical and limbic regions, are strongly involved in sex-specific aggressive and reproductive activities of rodents living in their natural habitats.
