Changes in hypothalamic catecholamine levels in relation to season, ovariectomy, and 17β-estradiol replacement in the catfish, Clarias batrachus (L.)

Manickam, P E Sampson; Joy, K.P.

doi:10.1016/0016-6480(90)90161-e

Cited by 20 publications

(8 citation statements)

References 21 publications

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“…Therefore, OE2 acts directly on MAO, as has been shown in other teleosts (Manickam & Joy 1989, Khan & Joy 1991, to modify 5-HT and other MA metabolism (Manickam & Joy 1990, Saligaut et al 1992a). …”

Section: Discussionmentioning

confidence: 82%

“…However, the mechanism by which the steroids exert feedback control are not clearly understood. Some studies in fish indicate that oestradiol-17ß (OE9) influ¬ ences MA metabolism in the brain or hypothalamus (Manickam & Joy 1990, Saligaut et al 1992a) and the altered amine levels in turn may modify the secretion of gonadotrophin and other pituitary hormones. There is evidence to show that oxidative deamination by MAO is an important step in MA metabolism and is influenced by OE2 (Manickam &Joy 1989, Khan &Joy 1991, Saligaut et al 1992a, Sloley et at.…”

Section: Introductionmentioning

confidence: 98%

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Effects of ovariectomy and oestradiol replacement on hypothalamic serotonergic and monoamine oxidase activity in the catfish, Heteropneustes fossilis: a study correlating plasma oestradiol and gonadotrophin levels

Senthilkumaran

Joy²

1994

Journal of Endocrinology

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Hypothalamic serotonin (5-HT; content and turnover) and monoamine oxidase (MAO) activity were measured in female catfish, Heteropneustes fossilis, after ovariectomy and supplementation with oestradiol-17 beta (OE2) in the recrudescent and quiescent phases. These factors were correlated with changes in plasma levels of OE2 and gonadotrophin. In the quiescent phase (December), neither ovariectomy nor OE2 supplementation had any significant effect on 5-HT content and MAO activity. Plasma levels of OE2 and gonadotrophin were undetectable in both control and treated fish, indicating that there was no feedback effect. In the recrudescent phase (prespawning, May), ovariectomy caused biphasic responses of MAO activity and 5-HT content. The enzyme activity decreased significantly after 2, 3, 4 and 5 weeks but increased significantly 6 weeks after ovariectomy. The 5-HT content varied in a biphasic manner with a significant increase at 2, 3 or 4 weeks and a significant decrease in week 6; there being no effect in week 5. 5-HT turnover was inhibited significantly only in week 4 after ovariectomy and did not show a biphasic pattern. In the ovariectomized groups, the OE2 level decreased significantly in a progressive manner with a maximum reduction in week 6. The plasma level of gonadotrophin showed a significant bimodal pattern of increase with the peak in week 4 after ovariectomy, indicating a strong negative feedback effect of OE2. The bimodal pattern of pituitary gonadotrophin release could be correlated with a similar pattern of increase in 5-HT content. OE2 treatment of fish which had been ovariectomized 3 weeks previously had dose-dependent effects on the enzyme; the low dose (0.1 microgram/g body weight) was stimulatory and the higher doses (0.5, 1.0 and 5.0 micrograms/g body weight) were inhibitory. The reverse was true for 5-HT content. Serotonergic turnover increased significantly only in the groups given high doses (1.0 and 5.0 micrograms/g body weight). The low dose of OE2 (0.1 micrograms/g body weight) restored the gonadotrophin and OE2 levels to those of the sham-ovariectomized vehicle-treated control group, whereas the high doses (0.5, 1.0 and 5.0 micrograms/g body weight) decreased the release of gonadotrophin in a dose-dependent manner. Our results suggest that OE2 modulates MAO activity to alter hypothalamic 5-HT in a seasonally dependent manner. The ovariectomy-induced changes in plasma levels of gonadotrophin appear to be mediated, at least partly, by the feedback action of OE2 on 5-HT metabolism.

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Section: Discussionmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 98%

Effects of ovariectomy and oestradiol replacement on hypothalamic serotonergic and monoamine oxidase activity in the catfish, Heteropneustes fossilis: a study correlating plasma oestradiol and gonadotrophin levels

Senthilkumaran

Joy²

1994

Journal of Endocrinology

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“…Moreover, It has been known that administration of 17-β-estradiol to 3-week ovariectomized fish (Clarias batrachus) results in both seasonal and differential effects on the CA levels. After 3-weeks of ovariectomy, CA levels were elevated significantly in the preparatory, pre-spawning and spawning phases, and were unaltered in the post-spawning season 23 ) . Therefore, it is likely of interest to examine the effect of 17-β-estradiol on CA secretion evoked by various secretagogues.…”

Section: Resultsmentioning

confidence: 97%

Influence of 17-α-Estradiol On Catecholamine Secretion from the Perfused Rat Adrenal Gland

Park

Cho

et al. 1996

Korean J Intern Med

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Objectives:It has been known that adrenal corticosteroids influence the expression of adrenomedullary catecholamine-synthetizing enzymes and also suppress the emission of axonal-like processes in cultured chromaffin cells. In the present study, it was attempted to investigate the effect of 17-α-estradiol on catecholamine (CA) secretion evoked by acetylcholine(ACh), DMPP, McN-A-343. excess K+ and Bay-K-8644 from the isolated perfused rat adrenal gland.Methods:Mature male Sprague-Dawley rats were anesthetized with ether. The adrenal gland was isolated by the method of WaKade. A cannula used for perfusion of the adrenal gland was inserted Into the distal end of the renal vein. The adrenal gland, along with ligated blood vessels and the cannula, was carefully removed from the animal and placed on a platform of a leucite chamber.Results:The perfusion of 17-α-estradiol (1–100 uM) into an adrenal vein for 20 min produced relatively dose-dependent inhibition in CA secretion evoked by ACh (5.32 mM). DMPP (100 uM for 2 min). McN-A-343 (100 uM for 2 min) and Bay-K-8644 (10 uM for 4 min). while it did not affect the CA secretory effect of high K+ (56 mM), Also, in the presence of 17-β-estradiol, CA secretion of ACh, DMPP and McN-A-343, without any effect on excess K+-evoked CA sectretion was depressed. However, in adrenal glands pre-loaded with 17-α-estradiol (10 uM) plus tamoxifen (2 uM). which is known to be a selective antagonist of estrogen receptors (for 20 min), CA secretory responses evoked by ACh, DMPP and McN-A-343 were considerably recovered as compared to that of 17-α-estradiol only, but excess K+-induced CA secretion was not affected. However, pre-treatment with 17-α-estradiol in the presence of meclopramide(dopaminergic antagonist) did not affect the secretory effect of CA evoked by ACh, DMPP, McN-A-343 and high potassium.Conclusions:These results suggest that 17-α-estradiol causes the marked inhibition of CA secretion evoked by cholinergic receptor stimulation, but not that by excess K+, indicating strongly that this effect may be mediated by inhibiting the influx of extracellular calcium into the rat adrenomedullary chromaffin cells through the activation of inhibitory estrogen receptors, and it also plays a modulatory role in regulating CA secretion.

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“…It is likely that the steroid may prevent the binding of the drug with the enzyme through an unknown mechanism or the steroid may stimulate enzyme activity by phosphorylation especially at Ser-40 by protein kinase A [41]. Previous studies in teleosts have shown that hypothalamic CA activity is influenced by the circulating levels of E 2 [21,22,42,43]. In H. fossilis, ovarian E 2 varies seasonally and exerts feedback effects on hypothalamic CA activity depending on the season and concentration of the steroid administered [20,23,31,32].…”

Section: Discussionmentioning

confidence: 99%

Estradiol-17β modulates dose-dependently hypothalamic tyrosine hydroxylase activity inhibited by α-methylparatyrosine in the catfish Heteropneustes fossilis

Chaube

Joy

2011

Endocrine

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The brain is a target for organizational and activational effects of oestrogens synthesized de novo or transported from the peripheral organs. A neuroprotective role of oestrogens has been documented in a variety of vertebrates. In the present study in the catfish Heteropneustes fossilis, we have demonstrated that estradiol-17β (E(2)), the major circulating oestrogen at low dosages (0.05 and 0.1 μg/g body weight of fish for 3 days) stimulated hypothalamic tyrosine hydroxylase (TH) activity, and countered the negative effects of ovariectomy (3-week) or α-methylparatyrosine (α-MPT: 250 μg/g body weight, a competitive inhibitor of TH). In contrast, high dosages of E(2) (1 and 2 μg/g body weight of fish for 3 days) were inhibitory and further amplified the inhibitory effects of ovariectomy and α-MPT. The inhibiting role of E(2) was higher in gonad-active (prespawning) phase than gonad-inactive (resting phase) phase. The dual roles of E(2) may ensure a tight regulation of catecholaminergic activity, activating and inhibiting the system against wide fluctuations that are characteristic of seasonally breeding animals.

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Changes in hypothalamic catecholamine levels in relation to season, ovariectomy, and 17β-estradiol replacement in the catfish, Clarias batrachus (L.)

Cited by 20 publications

References 21 publications

Effects of ovariectomy and oestradiol replacement on hypothalamic serotonergic and monoamine oxidase activity in the catfish, Heteropneustes fossilis: a study correlating plasma oestradiol and gonadotrophin levels

Effects of ovariectomy and oestradiol replacement on hypothalamic serotonergic and monoamine oxidase activity in the catfish, Heteropneustes fossilis: a study correlating plasma oestradiol and gonadotrophin levels

Influence of 17-α-Estradiol On Catecholamine Secretion from the Perfused Rat Adrenal Gland

Estradiol-17β modulates dose-dependently hypothalamic tyrosine hydroxylase activity inhibited by α-methylparatyrosine in the catfish Heteropneustes fossilis

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