Central and Peripheral Catecholamine Innervation of the Rat Intermediate and Posterior Pituitary Lobes

Saavedra, Juan M.

doi:10.1159/000124087

Cited by 57 publications

(16 citation statements)

References 22 publications

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“…Upon microscopic examination, the neural lobe was markedly reduced in size, but no atrophy was apparent in the intermediate lobe. This is consistent with a report by Saavedra [25] showing that SS results in the decrease of protein in the neural lobe only.…”

Section: Protein Content O F the Posterior Pituitary And M Bh Followisupporting

confidence: 94%

Differential Effects of Pituitary Stalk-Section on Posterior Pituitary and Hypothalamic Contents of Prolactin-Releasing Factor, Oxytocin, Dopamine and Beta-Endorphin

Hyde¹,

Murai²,

Ben‐Jonathan³

1988

Neuroendocrinology

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We have recently shown that the posterior pituitary (neurointermediate lobe) contains a potent prolactin (PRL)-releasing factor (PRF) which is distinct from known PRL secretagogues. Posterior pituitary PRF appears to be a small peptide of an unknown cellular origin. Using pituitary stalk-sectioned (SS) male rats, the objectives of this study were: (1) to determine if PRF is transported from the hypothalamus or is synthesized within the pituitary gland, and (2) to compare changes in PRF activity with alterations in the posterior pituitary content of β-endorphin (β-END), oxytocin (OXY), and dopamine (DA). One or two weeks following pituitary SS or sham surgery (SHAM), acid extracts of the posterior pituitary and medial basal hypothalamus (MBH) were analyzed for their hormone content. PRF activity was assessed by determining the stimulation of PRL secretion from perifused anterior pituitary cells, DA was measured by HPLC, and OXY and β-END levels were determined by RIAs. OXY and DA concentrations in the posterior pituitary were reduced more than 95% at both 1 and 2 weeks after SS. PRF activity in the posterior pituitary was significantly reduced by 75 and 90%, 1 and 2 weeks after SS, respectively. In contrast, β-END levels in the posterior pituitary at these times increased 20 and 60%, as compared to SHAM rats. Unlike the posterior pituitary, OXY levels in the MBH increased 123% 1 week following SS, and 1,260% at 2 weeks. These increases may reflect the accumulation of OXY-containing secretory vesicles in the severed nerves. DA concentrations in the MBH showed a biphasic pattern. DA levels were initially decreased by 70%, and then increased, but remained 30% below SHAM levels. The reason for these alterations in DA levels is not clear. It is concluded that: (1) similar to OXY and DA, but unlike β-END, PRF is likely transported from the hypothalamus to the posterior pituitary, and (2) the low levels of PRF activity in the MBH suggest that PRF may be synthesized as a biologically inactive precursor, the amount of PRF in the MBH is too low to detect, or inhibitors of PRL secretion mask the PRF activity.

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Section: Protein Content O F the Posterior Pituitary And M Bh Followisupporting

confidence: 94%

Differential Effects of Pituitary Stalk-Section on Posterior Pituitary and Hypothalamic Contents of Prolactin-Releasing Factor, Oxytocin, Dopamine and Beta-Endorphin

Hyde¹,

Murai²,

Ben‐Jonathan³

1988

Neuroendocrinology

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“…A previous study on NIL-NE contents in animals sev eral days after SCGx indicated that the peripheral sympathetic nerve teminals are the site of about 40% of the total NIL-NE content [1], Our present results indicate that about 12 h after SCGx, NIL-NE contents start to decrease, to attain at 24-36 h a stable concentration of about 40-60% of controls. NE release from disintegrating nerve terminals during this decay can theo retically activate receptors at NIL effector cells [3,4], Therefore, to assess A VP release during the time of wallerian degeneration after SCGx could give a valuable information on the physiologi cal role of peripheral sympathetic nerve terminals in the regula tion of AVP release.…”

Section: Discussionsupporting

confidence: 66%

“…The origin of NE fibers is in part periph eral, as shown by the 40% decrease in the posterior pituitary NE content after bilateral superior cervical ganglionectomy (SCGx) [1]. One role for these fibers is the regulation of NIL blood flow [2],…”

mentioning

confidence: 99%

Anterograde Nerve Degeneration after Superior Cervical Ganglionectomy Coexists with a Decrease in Arginine Vasopressin Release in Rats

et al. 1991

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After bilateral superior cervical ganglionectomy (SCGx) in adult male rats, norepinephrine content of the pituitary neurointermediate lobe () decreased at 12–24 h after surgery to attain concentrations 40–60% of controls between 24 and 60 h after surgery. To assess arginine vasopressin (AVP) secretion during this time, plasma and -AVP levels were measured by radioimmunoassay. In sham SCGx controls, plasma AVP increased about 2-fold within 6 h after surgery and decreased thereafter, to attain presurgical values by 60 h after surgery. In SCGx rats, a significant increase in plasma AVP concentration was observed at the 6th h after surgery, as compared to presurgical concentrations, with a decrease to values significantly lower than those of presurgical controls at 16–18 h after SCGx. As compared to sham-operated rats, significantly higher plasma AVP levels 6 h after surgery and significantly lower plasma AVP levels 16–24 h after surgery were found. -AVP concentration in SCGx and sham-operated ras were significantly lower than presurgical levels at 6 h after surgery. SCGx rats had significantly higher amounts of AVP in at 16–24 h after surgery. The changes in plasma and -AVP levels found 6 or 16 h after SCGx or sham SCGx were unaffected by a prior pinealectomy. Two injections of the α₁-adrenoceptor blocker prazosin 45 and 90 min before sacrifice, alone or together with the β-blocker propranolol, prevented the increase in plasma AVP found in SCGx rats 6 h after surgery, and the decrease in plasma AVP and the increase of -AVP found 16 h after SCGx. Propranolol treatment did not modify AVP levels. Neither drug was effective to modify AVP levels in sham-operated controls. The results argue in favor of physiologically relevant projections from superior cervical ganglion neurons to the neurohypophysis which participate in control of AVP release.

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“…We can postulate four different sources: a) from the systemic circulation, b) locally released, c) from nerve terminals in the median eminence into the portal-hypophyseal blood, and d) from direct innervation of the sympathetic nervous system of brain origin or partly originating in the superior cervical ganglia (17).…”

Section: Discussionmentioning

confidence: 99%

Stimulatory effects of adenosine on prolactin secretion in the pituitary gland of the rat

Picanço-Diniz

Valênça

Favaretto

et al. 2002

Braz J Med Biol Res

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We investigated the effects of adenosine on prolactin (PRL) secretion from rat anterior pituitaries incubated in vitro. The administration of 5-N-methylcarboxamidoadenosine (MECA), an analog agonist that preferentially activates A2 receptors, induced a dose-dependent (1 nM to 1 µM) increase in the levels of PRL released, an effect abolished by 1,3-dipropyl-7-methylxanthine, an antagonist of A2 adenosine receptors. In addition, the basal levels of PRL secretion were decreased by the blockade of cyclooxygenase or lipoxygenase pathways, with indomethacin and nordihydroguaiaretic acid (NDGA), respectively. The stimulatory effects of MECA on PRL secretion persisted even after the addition of indomethacin, but not of NDGA, to the medium. MECA was unable to stimulate PRL secretion in the presence of dopamine, the strongest inhibitor of PRL release that works by inducing a decrease in adenylyl cyclase activity. Furthermore, the addition of adenosine (10 nM) mimicked the effects of MECA on PRL secretion, an effect that persisted regardless of the presence of LiCl (5 mM). The basal secretion of PRL was significatively reduced by LiCl, and restored by the concomitant addition of both LiCl and myo-inositol. These results indicate that PRL secretion is under a multifactorial regulatory mechanism, with the participation of different enzymes, including adenylyl cyclase, inositol-1-phosphatase, cyclooxygenase, and lipoxygenase. However, the increase in PRL secretion observed in the lactotroph in response to A2 adenosine receptor activation probably was mediated by mechanisms involving regulation of adenylyl cyclase, independent of membrane phosphoinositide synthesis or cyclooxygenase activity and partially dependent on lipoxygenase arachidonic acid-derived substances.

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Central and Peripheral Catecholamine Innervation of the Rat Intermediate and Posterior Pituitary Lobes

Cited by 57 publications

References 22 publications

Differential Effects of Pituitary Stalk-Section on Posterior Pituitary and Hypothalamic Contents of Prolactin-Releasing Factor, Oxytocin, Dopamine and Beta-Endorphin

Differential Effects of Pituitary Stalk-Section on Posterior Pituitary and Hypothalamic Contents of Prolactin-Releasing Factor, Oxytocin, Dopamine and Beta-Endorphin

Anterograde Nerve Degeneration after Superior Cervical Ganglionectomy Coexists with a Decrease in Arginine Vasopressin Release in Rats

Stimulatory effects of adenosine on prolactin secretion in the pituitary gland of the rat

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