Differential Regulation of Tuberohypophysial Dopaminergic Neurons Terminating in the Intermediate Lobe and in the Neural Lobe of the Rat Pituitary Gland

Lookingland, Keith J.; Farah, John M.; Lovell, Kathryn L.; Moore, Kenneth E.

doi:10.1159/000124066

Cited by 64 publications

(21 citation statements)

References 10 publications

(10 reference statements)

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“…Instead, the activity of DA neurons that terminate in the intermediate lobe is regulated by DA receptor-medi ated mechanisms [19], and in this respect these neurons are similar to the An and An neurons comprising the incertohypothalamic DA systems [17]. The separate loca tion of tuberoinfundibular and tuberohypophysial DA cell bodies within the hypothalamus are consistent with the distinct responses and regulatory mechanisms of these two neuronal system.…”

Section: Discussionmentioning

confidence: 76%

“…Frontal brain section (600 pm) beginning at approximately A9220 pm [15] were prepared in a cryostat (-9 °C) and the median emi nence was dissected from these sections according to a modifica tion [17] of the method of Palkovits [18]. The intermediate lobe was dissected from the frozen pituitaries as described previously [19]. Tissue samples were placed in 60 pi of 0.1 M phosphate-ci trate buffer (pH 2.5) containing 15% methanol and stored at -20 °C until assayed.…”

Section: Tissue Dissectionmentioning

confidence: 99%

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Evidence That Hypothalamic Periventricular Dopamine Neurons Innervate the Intermediate Lobe of the Rat Pituitary

et al. 1992

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The purpose of the present study was to provide neurochemical and endocrinological evidence that dopamine (DA) neurons terminating in the intermediate lobe of the rat pituitary originate in the periventricular nucleus of the hypothalamus. One week following surgical separation of the periventricular nucleus from the mediobasal hypothalamus, DA and 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations in the intermediate lobe were reduced by 50%, and this was accompanied by an increase in plasma α-melanocyte-stimulating hormone (α-MSH) concentrations. In contrast, this procedure had no effect on concentrations of prolactin in the plasma, or DA or DOPAC in the median eminence, the region of the mediobasal hypothalamus containing terminals of tuberoinfundibular DA neurons. Electrical stimulation of the periventricular nucleus increased the ratio of DOPAC/DA in the intermediate lobe and reduced the concentrations of α-MSH in the plasma, whereas in these same animals the DOPAC/DA ratio in the median eminence and concentrations of prolactin in the plasma were unaltered. These results indicate that approximately 50% of all the DA neurons terminating in the intermediate lobe of the rat pituitary originate in or project through the periventricular nucleus of the hypothalamus, and that these DA neurons regulate the secretion of α-MSH from intermediate lobe melanotrophs.

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Section: Discussionmentioning

confidence: 76%

Section: Tissue Dissectionmentioning

confidence: 99%

Evidence That Hypothalamic Periventricular Dopamine Neurons Innervate the Intermediate Lobe of the Rat Pituitary

et al. 1992

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“…TIDA axons terminate on a fenestrated capillary bed within the external zone of the median eminence (ME) which drains into long portal vessels (LPV) that transport DA to the AL of the pituitary gland [10, 11, 12, 13]. The role of TIDA neurons as the primary source of DA inhibiting PRL secretion is well established [14, 15, 16, 17, 18]. However, a growing importance has been assigned to THDA and PHDA in the regulation of PRL secretion [9, 14, 19].…”

Section: Introductionmentioning

confidence: 99%

“…The role of TIDA neurons as the primary source of DA inhibiting PRL secretion is well established [14, 15, 16, 17, 18]. However, a growing importance has been assigned to THDA and PHDA in the regulation of PRL secretion [9, 14, 19]. …”

Section: Introductionmentioning

confidence: 99%

Circadian Rhythms of Neuroendocrine Dopaminergic Neuronal Activity in Ovariectomized Rats

Sellix

Freeman²

2003

Neuroendocrinology

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Prolactin (PRL) secretion is inhibited by dopamine (DA) released from hypothalamic neuroendocrine neurons designated tuberoinfundibular (TIDA), tuberohypophyseal (THDA) and periventricular hypophyseal (PHDA) dopaminergic (DAergic) neurons. Since PRL is secreted in many physiological states with a circadian rhythm, the purpose of these experiments was to determine if patterns of neuroendocrine DAergic neuronal activity in rats are also circadian. The activity of neuroendocrine DAergic neurons, defined as DA turnover rate in nerve terminals and quantitated as the ratio of DOPAC (a primary DA metabolite) to DA content, was measured by high-performance liquid chromatography with electrochemical detection (HPLC-EC) in these populations of DA neurons of OVX rats. TIDA neurons exhibit a rhythm of activity in a light:dark cycle which free-runs in constant dark (DD) and is entrained by light, indicating that TIDA neuronal activity is circadian. THDA and PHDA neurons also display daily rhythms entrained to a photoperiod and PHDA neuronal activity free-runs in DD with a period of approximately 24 h. However, a significant rhythm of THDA neuronal activity was not detected under DD. In the OVX rat, the activities of TIDA and PHDA neurons, but not THDA neurons, describe all the characteristics of a circadian rhythm as they are both entrained by light, but only TIDA and PHDA neurons maintain a significant rhythm of activity under DD.

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“…TIDA axons terminate on fenestrated capillary beds within the external zone of the median eminence (ME) that drain into long portal vessels, transporting DA to the anterior lobe (AL) of the pituitary gland (8,10). TIDA neurons are well established as the primary PRL inhibitory neurons, although growing importance has been assigned to both THDA and PHDA neurons in the regulation of PRL secretion (13,21,43,52,61).…”

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confidence: 99%

Anatomical and functional characterization of clock gene expression in neuroendocrine dopaminergic neurons

Sellix

Egli²,

Poletini³

et al. 2006

American Journal of Physiology-Regulatory, Integrative and Comp

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Oscillations of gene expression and physiological activity in suprachiasmatic nucleus (SCN) neurons result from autoregulatory feedback loops of circadian clock gene transcription factors. In the present experiment, we have determined the pattern of PERIOD1 (PER1), PERIOD2 (PER2), and CLOCK expression within neuroendocrine dopaminergic (DAergic) neurons (NDNs) of ovariectomized (OVX) rats. We have also determined the effects of per1, per2, and clock mRNA knockdown in the SCN with antisense deoxyoligonucleotides (AS-ODN) on DA release from NDNs. Diurnal rhythms of PER1 and PER2 expression in tuberoinfundibular DAergic (TIDA) and periventricular hypophyseal DAergic (PHDA) neurons, peaked at circadian time (CT)18 and CT12, respectively. Rhythms of PER1 expression in tuberhypophyseal neuroendocrine DAergic (THDA) neurons were undetectable. Rhythms of PER2 expression were found in all three populations of NDNs, with greater levels of PER2 expression between CT6 and CT12. AS-ODN injections differentially affected DA turnover in the axon terminals of the median eminence (ME), neural lobe (NL) and intermediate lobe (IL) of the pituitary gland, resulting in a significant decrease in DA release in the early subjective night in the ME (TIDA), a significant increase in DA release at the beginning of the day in the IL (PHDA), and no effect in the NL (THDA). AS-ODN-treatment induced a rhythm of DA concentration in the anterior lobe, with greater DA levels in the middle of the day. These data suggest that clock gene expression, particularly PER1 and PER2, within NDNs may act to modulate diurnal rhythms of DA release from NDNs in the OVX rat.prolactin; dopamine; suprachiasmatic nucleus; hypothalamus DOPAMINE (DA) of hypothalamic origin exerts tonic inhibitory control over prolactin (PRL) secretion (for review see Ref. 17). DA is released directly into hypothalamo-hypophyseal portal blood from three populations of neuroendocrine DAergic neurons (NDNs) (5, 17). These subpopulations include the tuberoinfundibular DAergic (TIDA) and tuberohypophyseal neuroendocrine DAergic (THDA,A12) neurons with cell bodies in the arcuate nucleus (ARN) and periventricular hypophyseal DAergic (PHDA,A14) neurons with cell bodies in the periventricular region (5, 17). THDA and PHDA axons traverse the pituitary stalk and terminate on fenestrated short portal vessels within the neural (NL) and intermediate (IL) lobes of the pituitary gland (21). TIDA axons terminate on fenestrated capillary beds within the external zone of the median eminence (ME) that drain into long portal vessels, transporting DA to the anterior lobe (AL) of the pituitary gland (8, 10). TIDA neurons are well established as the primary PRL inhibitory neurons, although growing importance has been assigned to both THDA and PHDA neurons in the regulation of PRL secretion (13, 21, 43, 52, 61).We have observed diurnal rhythms of DA turnover in the nerve terminals of TIDA, THDA, and PHDA neurons in the ovariectomized (OVX) rat (57, 58). Whereas both TIDA and PHDA neurons display circadian ...

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Differential Regulation of Tuberohypophysial Dopaminergic Neurons Terminating in the Intermediate Lobe and in the Neural Lobe of the Rat Pituitary Gland

Cited by 64 publications

References 10 publications

Evidence That Hypothalamic Periventricular Dopamine Neurons Innervate the Intermediate Lobe of the Rat Pituitary

Evidence That Hypothalamic Periventricular Dopamine Neurons Innervate the Intermediate Lobe of the Rat Pituitary

Circadian Rhythms of Neuroendocrine Dopaminergic Neuronal Activity in Ovariectomized Rats

Anatomical and functional characterization of clock gene expression in neuroendocrine dopaminergic neurons

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