Feedback Effects on Central Mechanisms Controlling Neuroendocrine Functions

Martini, L.; Celotti, F.; Juneja, H. S.; Motta, Marcella; Zanisi, M.

doi:10.1007/978-1-4684-3396-8_20

Cited by 8 publications

(9 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The obser¬ vation that 3ß-diol was more effective than testoster¬ one, even if less effective than DHT and 3a-diol, in inhibiting LH secretion also confirms previous evi¬ dence (Zanisi et al 1973 ;Martini, Celotti, Juneja et al 1979;Loseva, Degtiar & Isachenkov, 1980;Eckstein et al 1981;Martini, 1982). The fact that testosterone propionate, DHT propionate and 3ß-diol dipropionate were more effective than the respective alcohols in depressing LH release is not surprising, since steroid esters are released from the injection site in a more continuous fashion than 'free' steroids, and consequently may provide more constant serum con¬ centrations of the active principles.…”

Section: Discussionsupporting

confidence: 85%

Testosterone metabolites do not participate in the control of hypothalamic LH-releasing hormone

Zanisi¹,

Celotti²,

Ferraboschi³

et al. 1986

Journal of Endocrinology

Self Cite

View full text Add to dashboard Cite

To determine whether the ability of testosterone to increase intrahypothalamic LH-releasing hormone (LHRH) in orchidectomized rats might be explained by the conversion of the hormone into either its 5 alpha-reduced or oestrogenic metabolites, testosterone, 5 alpha-androstan-17 beta-ol-3-one (DHT), 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol) and 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol) (2 mg/rat per day for 6 days) and oestradiol (0.1, 0.5, 1.0 and 5.0 micrograms/rat per day for 6 days) were injected into castrated male rats. After 6 days the rats were killed and serum LH levels and intrahypothalamic LHRH stores measured using specific radioimmunoassay procedures. Testosterone and its 5 alpha-reduced metabolites were used in either the free alcohol or the propionate form (dipropionates in the case of the diols); oestradiol was used as oestradiol-17 beta or in the benzoate form. Treatment with testosterone, DHT, 3 alpha-diol and 3 beta-diol resulted in a significant decrease in serum LH levels; all the 5 alpha-reduced testosterone derivatives were more effective than testosterone in this respect. Testosterone and DHT propionates suppressed LH release following orchidectomy totally; 3 alpha-diol and 3 beta-diol dipropionates were less effective. Testosterone increased intrahypothalamic LHRH stores, this effect being much higher after testosterone propionate, i.e. when intrahypothalamic LHRH stores were restored to pre-castration levels. None of the 5 alpha-reduced steroids was capable of modifying the low intrahypothalamic levels of LHRH found following orchidectomy; only 3 alpha-diol dipropionate exhibited some activity, but this was much lower than that of testosterone propionate. Oestradiol-17 beta was totally ineffective in decreasing serum LH in orchidectomized animals; in contrast, oestradiol benzoate progressively decreased serum LH.(ABSTRACT TRUNCATED AT 250 WORDS)

show abstract

Section: Discussionsupporting

confidence: 85%

Testosterone metabolites do not participate in the control of hypothalamic LH-releasing hormone

Zanisi¹,

Celotti²,

Ferraboschi³

et al. 1986

Journal of Endocrinology

Self Cite

View full text Add to dashboard Cite

show abstract

“…Serotoninergic receptors of the types 5-HT1A, 5-HT1B, 5-HT2 and 5-HT3 may mediate the effect of 5-HT and stress on PRL secretion in adulthood (10,(16)(17)(18)(19). Our results also show that activation of 5-HT1A receptors increased PRL secretion in prepubertal males, which agrees with data obtained in adult males (12) and prepubertal females (13).…”

Section: Discussionsupporting

confidence: 91%

“…To select the prepubertal age when activation of the serotoninergic system stimulated PRL secretion, 4-, 8-, 12and 16-day-old male rats were decapitated 30 min after injecting (at 10.00 h) vehicle or 5-HTP (100 mg/kg, ip). Males castrated on day 13 and implanted either with silastic capsules containing testosterone or with empty capsules were injected sc on day 16 with vehicle or 10 mg/kg fluoxetine (-120 min) and with vehicle or 100mg/kg 5-HTP (-60min). Trunk bipod was allowed to clot at 4°C.…”

Section: Animals and Drugsmentioning

confidence: 99%

See 1 more Smart Citation

Serotoninergic control of prolactin secretion in prepubertal male rats

Aguilar

Ranchal²,

Tena‐Sempere³

et al. 1994

European Journal of Endocrinology

View full text Add to dashboard Cite

The role of the serotoninergic system in the control of prolactin (PRL) secretion has been studied in prepubertal male rats. Serum PRL concentration was measured in 16-day-old male rats at different times after the administration of 5-hydroxytryptophan (5-HTP), a precursor of serotonin (5-HT) synthesis, alone or in combination with fluoxetine, a specific inhibitor of 5-HT uptake; DL-p-parachlorophenylalanine (PCPA), an inhibitor of 5-HT synthesis; and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), a selective agonist of 5-HT1A receptors. Also, serum PRL concentration and pituitary content were measured after 5-HTP administration in castrated males implanted with silastic capsules containing testosterone or 5 alpha-androstane-3 alpha,17 beta-diol (alpha-diol). We found that: the reduction in serotoninergic activity after PCPA administration did not modify serum PRL concentrations; the stimulatory effect of 5-HTP on PRL secretion was not observed before day 16; the effects of 5-HTP or 5-HTP and fluoxetine were similar in intact and orchidectomized males; a significant increase in PRL secretion took place after 8-OH-DPAT administration; the duration of the stimulatory effect of 5-HTP increased after alpha-diol treatment; and pituitary PRL content increased after 5-HTP injection in intact males and decreased in castrated males treated with testosterone or alpha-diol.(ABSTRACT TRUNCATED AT 250 WORDS)

show abstract

“…Actually, a reduction of GnRH effectiveness has been reported after systemic administration of DHT and 3a-diol (14). The biological efficiency of androgen metabolites as pituitary modulators is different, diols being more effective than testosterone in suppressing LH release in orchidectomized males (15,16). Gonadal steroids also modulated pituitary responsive¬ ness to GHRH: orchidectomy in adulthood decreased pituitary responsiveness to GHRH both in vivo (4) and in vitro (3,17), and this response was restored in orchidec¬ tomized animals treated with testosterone (3,17,18).…”

Section: Discussionmentioning

confidence: 91%

5-α androstane diol stimulates the pituitary growth hormone responsiveness to growth hormone releasing hormone more effectively than testosterone or dihydrotestosterone in rats

Aguilar

Tena‐Sempere²,

Pinilla³

1992

Acta Endocrinologica

View full text Add to dashboard Cite

L. 5-a androstane diol stimulates the pituitary growth hormone responsiveness to growth hormone releasing hormone more effectively than testosterone or dihydrotestosterone in rats. Acta Endocrinol 1992;126:162-6. ISSN 0001-5598 The effect of different androgens and estradiol on pituitary responsiveness to growth hormone releasing hormone was studied in intact and orchidectomized adult male Wistar rats, by injecting subcutaneously immediately after orchidectomy for two weeks with testosterone, dihydrotestosterone, 5-\g=a\ androstane, 3-\g=a\,17 \g=b\-diol or estradiol dissolved in olive oil (in doses of 0.2 or 2.0 mg\m=.\kg-1 \m=.\day-1) or vehicle. Pituitary responsiveness was tested in pentobarbital anaesthetized rats by measuring growth hormone plasma levels at different times after administration of growth hormone releasing hormone (1-29) NH2. We found that: (a) High doses of testosterone, dihydrotestosterone and 5-\g=a\androstane, 3-\g=a\,17 \g=b\-diol restored gonadotropin plasma concentrations and organ weights altered by orchidectomy; (b) both pituitary growth hormone content and concentration remained unaffected after orchidectomy or androgen replacement and decreased significantly after estradiol injection; (c) orchidectomy significantly reduced growth hormone-stimulated growth hormone releasing hormone secretion; (d) treatment with 5-\g=a\androstane, 3-\g=a\, 17 \g=b\-diol increased more than testosterone or dihydrotestosterone both the peak concentration and the mean growth hormone secretion after growth hormone releasing hormone stimulation: (e) no differences were observed in the treatment with testosterone or dihydrotestosterone; (f) estradiol given at a dose of 0.2 mg\m=.\kg-1\m=.\day-1 increased pituitary responsiveness to growth hormone releasing hormone. These results demonstrated that testosterone and 5-\g=a\androstane, 3-\g=a\, 17 \g=b\-diol, which do not differ in their action on pituitary growth hormone content, increased the pituitary responsiveness to growth hormone releasing hormone differently and that the low pituitary responsiveness to growth hormone releasing hormone previously described in prepubertal animals was not due mainly to the secretion of 5-\g=a\androstane, 3-\g=a\,17 \g=b\-diol.Pituitary secretion of GH in response to GHRH increased with age (1-5) and after testosterone treatment (2). However, the role of the testis in the control of GHRHinduced GH release is controversial and we have recently described (4) how the increase in pituitary responsive¬ ness to GHRH with age is independent of the testis and occurs in orchidectomized animals. The effect of orchi¬ dectomy depended on the age of the rats and on the time elapsed after orchidectomy, since an increase in pituitary responsiveness to GHRH was observed a week after orchidectomy in prepubertal animals, whereas in adult males orchidectomy decreased the effectiveness of GHRH. Since the prepubertal testis secretes mainly 5-a androstane, 3-a, 17 /?-diol (a-diol) (6, 7), we suggested that this steroid, unlike testosterone, may...

show abstract

Feedback Effects on Central Mechanisms Controlling Neuroendocrine Functions

Cited by 8 publications

References 46 publications

Testosterone metabolites do not participate in the control of hypothalamic LH-releasing hormone

Testosterone metabolites do not participate in the control of hypothalamic LH-releasing hormone

Serotoninergic control of prolactin secretion in prepubertal male rats

5-α androstane diol stimulates the pituitary growth hormone responsiveness to growth hormone releasing hormone more effectively than testosterone or dihydrotestosterone in rats

Contact Info

Product

Resources

About