Effects of Dopamine Implanted in the Median Eminence on the Estrous Cycle of the Rat

Uemura, Hirotsugu; Kobayashi, Hideshi

doi:10.1507/endocrj1954.18.91

Cited by 30 publications

(8 citation statements)

References 12 publications

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“…It seemed un likely that the infused agent could have remained in situ for more than a matter of hours, as would have been the case with the chronic dopa mine-cholesterol implants of Uemura and Kobayashi [1971], yet restoration of responsiveness to NE in some instances required several weeks. It appeared more likely that recovery involved some regenerative process such as that required to restore function to adrenergic nerve endings following treatment with 6-hydroxydopamine (6-OH-DA).…”

Section: Discussionmentioning

confidence: 99%

Effects of Intraventricular Infusions of Norepinephrine and Dopamine on LH Release and Ovulation in the Rabbit

Sawyer¹,

Hilliard²,

Kanematsu³

et al. 1974

Neuroendocrinology

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The infusion of 50 µg norepinephrine (NE) into the third ventricle of the brain was found to be highly effective in stimulating the release of an ovulatory surge of LH from the pituitary gland in estrogen-primed rabbits. Intraventricular dopamine (D), in dosages of 5 and 50 µg, was not only completely ineffective in inducing ovulation, but the higher dosage actually blocked the ovulatory effect of NE, often for a month or more after infusion. In experimentts in which LH was measured by radioimmunoassay, intraventricular NE stimulated a marked rise in LH starting within minutes, peaking at 2 h and returning to pre-infusion levels by 6 h. No rise in serum LH was observed following the intraventricular infusion of D. Both dosages of D were quite effective in blocking LH output in response to NE infused 2 h later, and the 50-µg dosage of D generally prevented any rise in serum LH concentration for some weeks after the infusion of intraventricular NE. The results are consistent with the hypothesis that a noradrenergic synapse is functional in hypothalamic mechanisms activating the release of pituitary LH.

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Section: Discussionmentioning

confidence: 99%

Effects of Intraventricular Infusions of Norepinephrine and Dopamine on LH Release and Ovulation in the Rabbit

Sawyer¹,

Hilliard²,

Kanematsu³

et al. 1974

Neuroendocrinology

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“…Other laboratories [1,8,II,18,22] as well as our own (6,7,9] have previously indicated an inhibitory role for DA in the regulation of LH secretion in rats. The response to DA has also been shown to depend on the steroid background in rats [9] and humans [13].…”

Section: Discussionmentioning

confidence: 69%

Further Studies on Dopamine-Induced Suppression of Pulsatile LH Release in Ovariectomized Rats

Gallo¹

1981

Neuroendocrinology

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Third ventricular administration of dopamine (DA) in ovariectomized rats suppresses pulsatile LH secretion in a dose-dependent manner (Neuroendocrinology 29: 149, 1979). Since infusion of norepinephrine (NE) also produces a similar response, and DA can be taken up by noradrenergic fibers and converted to NE, an experiment was carried out to determine whether DA acted by directly activating DA receptors. This study also examined which parameters of pulsatile LH secretion were affected during DA-induced suppression of this release process, i.e., the LH interpulse interval and/or the magnitude of increase in blood LH levels produced by LH pulses. Infusion of DA in control rats pretreated with tartaric acid or /-butaclamol decreased mean blood LH levels. This effect is due entirely to a marked increase in the LH interpulse interval, since no change was seen in the magnitude of increase in blood LH levels produced by those LH pulses that did occur during DA infusion. Blockade of DA receptors with pimozide prevented the decrease in blood LH levels in response to DA and significantly reduced the change in the LH interpulse interval. These data indicate that DA suppresses pulsatile LH release solely by affecting the periodicity of this rhythm, and that this effect is mediated primarily through an activation of DA receptors. Pretreatment with d-butaclamol, another DA receptor antagonist, had no effect on the response to DA. As in control rats, DA-induced suppression of pulsatile LH release was again due entirely to a lengthening of the LH interpulse interval. d-Butaclamol does block the inhibition of pulsatile LH release due to peripheral administration of the DA receptor agonist, apomorphine (Endocrinology 100: 796, 1977). However, when concentrations of apomorphine equimolar to DA were infused into the third ventricle in d- or l-butaclamol-treated rats, comparable suppressions of pulsatile LH release occurred. This suggests that the failure of d-butaclamol to prevent the suppression of pulsatile LH release by intraventricular DA administration was apparently due to an ineffective level of DA receptor blockade.

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“…However, there are results which support the opposite hypothesis, namely that dopaminergic neurones exert an inhibitory effect upon gonadotrophin release (Fuxe et al 1969(Fuxe et al , 1972Ähren et al 1971). These studies, based largely on turnover studies and histofluorometric techniques, are supported by the findings of Uemura & Kobayashi (1971 ) who showed that dopamine implants in the medial basal hypothalamus inhibited ovulation and produced prolonged dioestrus. The results from the present study also show that high doses of dopamine are in themselves inhibitory (Table 1) and this would agree with the above hypothesis.…”

Section: Discussionmentioning

confidence: 70%

The Effect of Intrahypothalamic Infusions of Dopamine and Noradrenaline on Ovulation in Reserpine-Treated Female Rats

Craven¹,

McDonald²

1973

Journal of Endocrinology

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Cyclic female rats were treated with reserpine (5 mg/kg) on the 2nd day of dioestrus (15.00 h) or on the day of pro-oestrus (11.30 h) to produce a total or partial depletion of brain amines. Ovulation was inhibited in 18 out of 21 rats. Intrahypothalamic infusions of 0\m=.\4\p=n-\80 \ g=m\ gdopamine or noradrenaline on the afternoon of pro-oestrus did not restore ovulation in reserpine-treated rats. In normal pro-oestrous rats, 80 \g=m\gdopamine significantly inhibited ovulation, whereas 80 \g=m\g noradrenaline had no significant effect. Electrochemical stimulation of the basal hypothalamus or the administration of luteinizing hormone induced ovulation only in those animals treated with reserpine at pro-oestrus. The results indicate that reserpine exerts a marked peripheral effect when given on the 2nd day of dioestrus and has a partial effect on the ovaries when administered at pro-oestrus. The failure of monoamines to induce ovulation suggests that some aminergic synapses involved in gonadotrophin release may lie outside the medial basal hypothalamus. In addition, high levels of dopamine appear to exert an inhibitory action on the release of pituitary gonadotrophins.

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Effects of Dopamine Implanted in the Median Eminence on the Estrous Cycle of the Rat

Cited by 30 publications

References 12 publications

Effects of Intraventricular Infusions of Norepinephrine and Dopamine on LH Release and Ovulation in the Rabbit

Effects of Intraventricular Infusions of Norepinephrine and Dopamine on LH Release and Ovulation in the Rabbit

Further Studies on Dopamine-Induced Suppression of Pulsatile LH Release in Ovariectomized Rats

The Effect of Intrahypothalamic Infusions of Dopamine and Noradrenaline on Ovulation in Reserpine-Treated Female Rats

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