Ovarian-Steroid Modulation of Locus Coeruleus Activity in Female Rats: Involvement in Luteinising Hormone Regulation

The noradrenergic nucleus locus coeruleus (LC) has been reported to regulate luteinising hormone (LH) secretion in female rats. Both oestrogen and progestin receptors have been demonstrated in LC neurones, suggesting that these cells are possibly responsive to variations in circulating levels of ovarian steroids. We therefore evaluated changes in the activity of LC neurones during the oestrous cycle and after ovarian-steroid treatment in ovariectomised (OVX) rats, as determined by immunoreactivity to Fos-related antigens (FRA), which comprises all of the known members of the Fos family. Effects of ovarian steroids on the firing rate of LC neurones were also determined in a slice preparation. The number of FRA/tyrosine hydroxylase (TH)-immunoreactive (ir) neurones in the LC increased from 14.00-16.00 h on pro-oestrus, coinciding with the onset of the LH surge and rise in plasma progesterone. FRA immunoreactivity was unaltered during dioestrus. Oestradiol-treated OVX rats (OVX+E) displayed marked reduction in FRA/TH-ir neurones in LC compared to oil-treated OVX rats. Accordingly, oestradiol superfusion significantly reduced the spontaneous firing rate of LC neurones in slices from OVX rats. Compared to OVX+E, oestradiol-treated rats injected with progesterone at 08.00 h (OVX+EP) exhibited higher number of FRA/TH-ir neurones in the LC at 10.00 h and 16.00 h, and great amplification of the LH surge. Bath application of progesterone significantly increased the spontaneous firing rate of OVX+E LC neurones. Our data suggest that ovarian steroids may physiologically modulate the activity of LC neurones in females, with possible implications for LH secretion. Moreover, oestradiol and progesterone appear to exert opposite and complementary effects (i.e. whereas oestradiol inhibits, progesterone, after oestradiol priming, stimulates LC activity).

Anabolic-androgenic steroid treatment induces behavioral disinhibition and downregulation of serotonin receptor messenger RNA in the prefrontal cortex and amygdala of male mice

Nandrolone is an anabolic-androgenic steroid (AAS) that is highly abused by individuals seeking enhanced physical strength or body appearance. Supraphysiological doses of this synthetic testosterone derivative have been associated with many physical and psychiatric adverse effects, particularly episodes of impulsiveness and overt aggressive behavior. As the neural mechanisms underlying AAS-induced behavioral disinhibition are unknown, we investigated the status of serotonergic system-related transcripts in several brain areas of mice receiving prolonged nandrolone administration. Male C57BL/6J mice received 15 mg/kg of nandrolone decanoate subcutaneously once daily for 28 days, and different sets of animals were used to investigate motor-related and emotion-related behaviors or 5-HT-related messenger RNA (mRNA) levels by real-time quantitative polymerase chain reaction. AAS-injected mice had increased body weight, were more active and displayed anxious-like behaviors in novel environments. They exhibited reduced immobility in the forced swim test, a higher probability of being aggressive and more readily attacked opponents. AAS treatment substantially reduced mRNA levels of most investigated postsynaptic 5-HT receptors in the amygdala and prefrontal cortex. Interestingly, the 5-HT(1B) mRNA level was further reduced in the hippocampus and hypothalamus. There was no alteration of 5-HT system transcript levels in the midbrain. In conclusion, high doses of AAS nandrolone in male mice recapitulate the behavioral disinhibition observed in abusers. Furthermore, these high doses downregulate 5-HT receptor mRNA levels in the amygdala and prefrontal cortex. Our combined findings suggest these areas as critical sites for AAS-induced effects and a possible role for the 5-HT(1B) receptor in the observed behavioral disinhibition.

Antiprotozoan activity of Brazilian marine cnidarian extracts and of a modified steroid from the octocoral Carijoa riisei

In the present investigation, we have evaluated the antileishmanial and antitrypanosomal activity of methanolic crude extracts obtained from eight species of cnidarians and of a modified steroid isolated from the octocoral Carijoa riisei. The antileishmanial activity of cnidarians crude extracts showed 50% inhibitory concentration ( IC50) values in the concentration range between 2.8 and 93.3 mu g/mL. Trypomastigotes of Trypanosoma cruzi were less susceptible to the crude extracts, with IC50 values in the concentration range between 40.9 and 117.9 mu g/mL. The steroid (18-acetoxipregna-1,4,20-trien-3-one) displayed a strong antileishmanial activity, with an IC50 value of 5.5 mu g/mL against promastigotes and 16.88 mu g/mL against intracellular amastigotes. The steroid also displayed mammalian cytotoxicity (IC50 of 10.6 mu g/mL), but no hemolytic activity was observed at the highest concentration of 12.5 mu g/mL. The antileishmanial effect of the steroid in macrophages suggested other mechanism than macrophage activation, as no upregulation of nitric oxide was observed. The antitrypanosomal activity of the steroid resulted in an IC50 value of 50.5 mu g/mL. These results indicate the potential of cnidarian natural compounds as antileishmanial drug candidates.

Steroid 21-hydroxylase expression in cultured rat astrocytes

Over the past decade or so it has become widely recognised that the brain is a significant steroidogenic organ. Many publications have highlighted the ability of the brain to synthesise and interconvert a large number of steroid products including cholesterol, progesterone and testosterone. In this study, in vitro experiments were performed to determine if 21-hydroxylation of steroids is undertaken by rat brain astrocytes in culture. This is a common reaction that occurs in the adrenal gland and other organs in mammals, catalysing the conversion of pregn-4-ene-3,20-dione (progesterone) to 21-hydroxypregn-4-ene-3,20-dione (deoxycorticosterone).

Previous reports have indicated that 21-hydroxylation occurs within the rat brain, however, the precise identity of the cells expressing 21-hydroxylase has not yet been determined. Several metabolites, such as 5α-pregnan-3α-ol-20-one (tetrahydroprogesterone) and 3α,21-dihydroxy-5-pregnan-20-one (tetrahydrodeoxycorticosterone) were of particular interest because of their modulatory role in neuronal function, such as their agonist activity at γ-aminobutyric acid (GABA_A) receptors.

Evidence was obtained for the expression of peripheral 21-hydroxylase enzyme (P450c21) in cultured rat brain astrocytes by a combination of mass spectroscopy and molecular biology techniques. This is a significant finding as expression of 21-hydroxylase within astrocytes may be indicative of a wider role for these cells in modulating neuronal behaviour.

Environmental factors affecting transcription of the human L1 retrotransposon. I. Steroid hormone-like agents

The L1 retrotransposon has significantly shaped the structure of the human genome. At least 30% of human genome sequence can be attributed to L1 reverse transcriptase activity. There are 105 copies of the human L1 retrotransposon, L1Hs, most of which are defective, although ~8–9x103 are full length. L1Hs elements transpose through an RNA intermediate and transcription is thought to be the rate limiting step in retrotransposition. Because transcription of retrotransposons in a variety of organisms has been shown to respond to environmental stimuli, we investigated the influence of various agents on transcription from two different L1Hs promoters. The activity of the L1Hs promoters was analyzed by transfecting L1Hs-expressing cell lines with plasmids containing the L1Hs promoters fused to the LacZ reporter gene and monitoring expression with a ß-galactosidase assay. Small increases in ß-galactosidase activity were observed with both L1Hs promoters after treatment with serum, testosterone, dihydrotestosterone and organochloride pesticides, indicating that these agents can influence L1Hs transcription.

Single vs. two steroid injections for carpal tunnel syndrome: a randomised clinical trial

We investigated the efficacy of a single vs. double steroid injections in the treatment of carpal tunnel syndrome (CTS) in a randomised double-blind controlled trial. Patients with idiopathic CTS were randomised into (i) one group receiving a baseline methylprednisolone acetate injection plus a saline injection 8 weeks later and (ii) a second group receiving methylprednisolone acetate injection at baseline and at 8 weeks. The primary outcome was the Global Symptom Score (GSS). Forty patients were recruited. By 40 weeks, the mean GSS improved from 25.6 to 14.1 in the single-injection group whereas from 26.7 to 12.6 in the reinjection group, but there was no significant difference in GSS between the two groups (p = 0.26). There were also no significant differences in terms of electrophysiological and functional outcomes. The results suggest that an additional steroid injection confers no added benefit to a single injection in terms of symptom relief.

Is sex-specific mass gain in Cory's shearwaters Calonectris diomedea related to begging and steroid hormone expression?

Mass differences between the sexes of dimorphic bird species often appear early in the nestling development. But how do adults know how much to feed a chick in a sexually dimorphic species? Do chicks of the heavier sex beg more? We studied begging in Cory’s shearwaters Calonectris diomedea, a species with heavier adult and juvenile males than females. We found that begging rates and call numbers were not different between male and female chicks, but parameters of begging intensity differed between the sexes in their relationship to chick body condition. For the same body condition, males had significantly higher begging call numbers and rates. Acoustical parameters, which were analysed semi-automatically, included the lengths of call and silence intervals, the minimum, mean and maximum frequency in a call and the number of frequency peaks within a call. We found no consistent differences of acoustic begging call elements between the sexes. Male and female chicks did not differ in the levels of the steroid hormones testosterone or corticosterone in the second quarter of the nestling period, and the mechanism leading to sex-related differences in begging rates for a given body condition remains unknown.

Cortisol delays the estradiol-induced LH surge : is this dependent on prior ovarian steroid exposure?

Glucocorticoids can inhibit pulsatile LH secretion and can delay or even block the preovulatory LH surge. Previous work in ovariectomized ewes has indicated that cortisol can delay the estradiol-induced LH surge in an artificial follicular phase model but the results suggest this effect may be influenced by prior exposure to ovarian steroids. Here we tested the hypothesis that this disruptive effect of cortisol on the positive feedback action of estradiol is dependent on prior exposure to the ovarian steroidal milieu of the estrous cycle. Using long-term ovariectomized ewes, sequential artificial estrous cycles were created in the anestrous season by treatment and subsequent withdrawal of progesterone (CIDRs inserted for 9 d) followed by estradiol implants simulating the pre-ovulatory estradiol rise that induces the LH surge. Following the first artificial estrous cycle, a second cycle was initiated. Progesterone was again administered for 9 d followed by a second artificial follicular phase two weeks later. Beginning 2 hr prior to estradiol administration and ending at 40 hr, animals received either a cortisol infusion (elevate plasma levels to ∼170 ng/ml) or vehicle. Jugular blood was sampled hourly to assess occurrence and timing of the LH surge. Four different treatment sequences were tested (Cycle 1-Cycle 2): cortisol-cortisol; vehicle-cortisol; cortisol-vehicle; and vehicle-vehicle (n=5-6/sequence). If prior exposure to the ovarian steroidal milieu of the estrous cycle was necessary for cortisol to interfere with the positive feedback action of estradiol, then we would predict that cortisol would only delay the LH surge when it was delivered in Cycle 2 but not Cycle 1. Our results failed to support this prediction. Cortisol delayed the surge in both cycles (p<0.01), and the extent of the delay was the same in both Cycles 1 and 2 (4 hrs). Cortisol did not significantly affect surge amplitude in either cycle. These findings reinforce our previous conclusion that cortisol can delay the estradiol-induced LH surge but they do not support the hypothesis that this action of cortisol is dependent upon exposure to the ovarian steroidal milieu of the previous estrous cycle. (NIH-HD-30773)

Steroid metabolism in cultured mammalian astrocytes

This thesis explores the metabolism of the steroid progesterone within both rat and mouse brain cells in culture. The research identified a steroid 21-hydroxylase within the rat culture system, that has downstream implications on stress and behaviour. Novel uses for a stain to accurately discriminate two brain celltypes were discovered.

Steroid acyl transferase activity in the mammalian brain

This thesis investigates steroid fatty acid esters (which may have a possible role in myelination of the central nervous system) in mammalian brain. While these conjugates are abundant in brain tissue, little is known about their biological role. When measuring steroid acyl transferase activity, the optimum substrate concentration was found to vary significantly between the sheep and rat brain. Results also indicated that different enzymes may act to esterify different steroid substrates.