Effects of dopamine and norepinephrine on spontaneous and gonadotropin-releasing hormone-induced gonadotropin release by dispersed cells or fragments of the goldfish pituitary

Chang, John P.; MacKenzie, Duncan S.; Gould, David R.; Peter, Richard

doi:10.1016/0024-3205(84)90559-9

Cited by 73 publications

(26 citation statements)

References 17 publications

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“…Similar results have been reported for the goldfish (Chang et al, 1984;MacKenzie et al, 1984 (Rubin, 1982 (Limor et al, 1987 (Conn et al, , 1980Harris et al, 1985 (Reuter, 1983;Ovichinnikov, 1985 (Hopkins and Walker, 1978;Stern and Conn, 1981;Gorospe and Conn, 1987) and in fish (Jamaluddin et al, 1989 (Jamaluddin et al, 1989) Alberta, Canada, 1988 (abstract 49).…”

Section: Gth Determination and Statisticssupporting

confidence: 76%

Calcium ions as a mediator in GnRH action on gonadotropin release in the common carp (Cyprinus carpio L)

Mikołajczyk¹,

Weil²,

Epler³

et al. 1990

Reprod. Nutr. Dévelop.

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Section: Gth Determination and Statisticssupporting

confidence: 76%

Calcium ions as a mediator in GnRH action on gonadotropin release in the common carp (Cyprinus carpio L)

Mikołajczyk¹,

Weil²,

Epler³

et al. 1990

Reprod. Nutr. Dévelop.

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“…These observations confirm that besides GnRH-stimulated GTH secretion, basal GTH release in the goldfish is also subjected to dopamine D2 inhibition. The abil ity of dopamine and APO to reduce, and the dopamine antago nist pimozide to increase serum GTH levels in saline and GnRH-injected female goldfish [10,11], as well as the in vitro inhibitory actions of dopamine on basal and GnRH-induced GTH release from perifused goldfish pituitary cells and fragments [8] have been reported. The failure of APO to signifi cantly depress basal GTH release from static cultures of dis- persed goldfish pituitaiy cells [reported in Chang et al,5] may be due to the non selective nature of this dopamine agonist, as well as relative difficulties in demonstrating these differences in static incubation conditions.…”

Section: Discussionmentioning

confidence: 99%

Differential Actions of Dopamine Receptor Subtypes on Gonadotropin and Growth Hormone Release in vitro in Goldfish

Chang

Yu²,

Wong³

et al. 1990

Neuroendocrinology

129

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Incubation of cultured goldfish pituitary cells with 10 nM to 1 µM apomorphine (APO), a non-selective dopamine agonist, increased growth hormone (GH) release in a dose-dependent manner. GH release was also stimulated in a dose-dependent manner by 0.1 nM to 1 µM salmon gonadotropin (GTH)-releasing hormone (sGnRH), sGnRH analog, and chicken GnRH-II (cGnRH-II). The magnitude of GH responses to 1 µM GnRHs were less than that to 1 µM APO. GH responses to 10 nM to 1 µM APO were not significantly increased by the addition of GnRHs. Static incubations with 0.1 nM to 1 µM of the dopamine Dl agonist SKF38393 did not alter basal GTH release, or the GTH responses to 10 nM sGnRH and cGnRH-II. In contrast, the Dl agonist SKF38393 significantly increased basal GH secretion with maximal stimulation achieved at 100 nM concentration, and GH responses to 10 nM sGnRH and 10 nM cGnRH-II were enhanced by simultaneous applications of SKF38393. Incubation with 1 µM of the D2 agonist LY171555 decreased basal GTH release. Additions of 0.1 nM to 1 µM LY171555 caused dose-dependent decreases in the GTH secretion induced by 10 nM sGnRH and cGnRH-II. In contrast, basal and GnRH-stimulated GH release were not affected by coincubations with LY171555. The Dl antagonist SKF83566 and the D2 antagonist domperidone, at 1 µM concentrations, specifically blocked the Dl agonist SKF38393-stimulated increase in GH release and the D2 agonist LY171555-induced depression of GTH secretion, respectively. In cell column perifusion studies, the Dl agonist SKF38393 at 0.1 nM to 1 µM had no effects on GTH release, but significantly elevated GH secretion rates when applied at 0.1–1 µM concentrations. The GH release induced by 1 µM SKF38393 was significantly reduced by simultaneous perifusion with 1 µM of the Dl antagonist SKF83566. Treatments with SKF38393 and/or SKF83566 did not affect net GTH and GH responses to sGnRH challenges. In contrast, perifusion with 0.1 and 1 µM of the D2 agonist LY171555 depressed basal as well as sGnRH-induced GTH responses. These effects of 1 µM LY171555 were completely blocked by simultaneous applications of 1 µM domperidone, a D2 antagonist. Treatments with these D2 selective drugs did not affect basal and sGnRH-stimulated GH release. These results indicate that in cultured goldfish pituitary cells, activation of dopamine Dl- and D2-like receptors specifically stimulates GH release and inhibits both basal and stimulated GTH secretion, respectively. The presence of direct actions of sGnRH and cGnRH-II on goldfish GTH an GH release are also demonstrated. This is the first study do demonstrate stimulatory dopamine Dl actions in the vertebrate pituitary.

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“…This, together with the studies showing direct effects of dopamine to inhibit GnRHstimulated gonadotropin release at the level of the pituitary in goldfish (6,18], suggest that dopamine can act at the level of both brain GnRH neurons and pituitary gonadotrophs to influence gonadotropin secretion. An interaction of dopami nergic pathways with the GnRH peptidergic system is also sug gested by the anatomical proximity of the two neuronal sys tems.…”

Section: Effects O F Pimozide and Apomorphine On Levels O F Brain Gnrmentioning

confidence: 99%

“…Whether this entails actions of apo morphine at the brain and/or pituitary levels is not clear. It is known that in fish apomorphine and dopamine can cause a de crease in gonadotropin release in response to exogenous GnRH administration in vivo [24,25], as well as block the ef fects of GnRH on dispersed pituitary cells in vitro [6,18], indicating that action at the level of the pituitary gonadotrophs is likely. However, this does not explain the effects of apomor phine on brain GnRH levels in males exposed to PG females; the results support the idea that dopamine also has a central inhibitory effect on the brain GnRH neuronal system.…”

Section: Effects O F Apomorphine and Pimozide On Levels O F Brain Gnrmentioning

confidence: 99%

Dopaminergic Regulation of Brain Gonadotropin-Releasing Hormone in Male Goldfish during Spawning Behavior

Yu¹,

Peter²

1990

Neuroendocrinology

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Dopaminergic regulation of gonadotropin-releasing hormone (GnRH) concentrations in discrete brain areas of male goldfish was studied using the centrally active dopaminergic agonist apomorphine and antagonist pimozide. Pimozide caused time- and dose-dependent increases in serum gonadotropin levels and accumulation of GnRH in the olfactory bulbs, telencephalon and pituitary. The effects of pimozide were partially antagonized by apomorphine, which, when given alone, did not influence basal levels of brain GnRH and serum gonadotropin, but inhibited the increases in brain GnRH and serum gonadotropin levels that normally occur in response to spawning stimuli from prostaglandin-treated females. To study the physiological significance of the accumulation of brain GnRH due to central dopaminergic receptor blockade, the influences of pimozide on the brain GnRH and serum gonadotropin responses of male goldfish to spawning stimuli were tested. Pimozide pretreatment potentiated the serum gonadotropin increases and caused a marked reduction in the GnRH levels in olfactory bulbs, telencephalon and pituitary in response to spawning stimuli. These findings demonstrate that the central dopaminergic system is an important inhibitory component in the regulatory circuitry of brain GnRH levels in normal and behaviorally stimulated male goldfish.

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Effects of dopamine and norepinephrine on spontaneous and gonadotropin-releasing hormone-induced gonadotropin release by dispersed cells or fragments of the goldfish pituitary

Cited by 73 publications

References 17 publications

Calcium ions as a mediator in GnRH action on gonadotropin release in the common carp (Cyprinus carpio L)

Calcium ions as a mediator in GnRH action on gonadotropin release in the common carp (Cyprinus carpio L)

Differential Actions of Dopamine Receptor Subtypes on Gonadotropin and Growth Hormone Release in vitro in Goldfish

Dopaminergic Regulation of Brain Gonadotropin-Releasing Hormone in Male Goldfish during Spawning Behavior

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