Elevation of Plasma Prolactin After Hypophysial Stalk Section in the Rat1

Kanematsu, Shigeto; Sawyer, Charles H.

doi:10.1210/endo-93-1-238

Cited by 41 publications

(15 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…DA is transported via these vessels to the anterior pituitary where it inhibits PRL release. Pituitary SS severs the long portal vessels, removes the tonic inhibition of DA, and re sults in elevated plasma PRL levels [15], We observed a biphasic pattern of DA concentrations in the MBH following pituitary SS. The initial decline in DA may be the result of (I) increased DA release from TIDA neurons due to the increased plasma PRL levels [11], or (2) surgical trauma to the THDA/TIDA neurons.…”

Section: Discussionmentioning

confidence: 53%

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

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 53%

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

View full text Add to dashboard Cite

show abstract

“…First, the Lobex-induced rise in plasma PRL lev els was significantly lower than the 10-fold elevation seen after transection of the pituitary stalk [23]. Second, Lobex performed under Brevital anesthesia in the morning of proestrus did not prevent ovulation \ Murai and Ben-Jonaihan.…”

Section: Discussionmentioning

confidence: 91%

Chronic Posterior Pituitary Lobectomy: Prolonged Elevation of Plasma Prolactin and Interruption of Cyclicity

Murai¹,

Ben‐Jonathan²

1986

Neuroendocrinology

View full text Add to dashboard Cite

We previously reported that the posterior pituitary dopaminergic system participates in the inhibition of prolactin (PRL) secretion in both male and lactating female rats. However, posterior pituitary lobectomy (Lobex) of urethane-anesthetized cycling rats resulted in an elevation in plasma PRL for a short time only. This raises a question regarding the importance of input from the posterior pituitary to the control of PRL secretion during the estrous cycle. The objectives of this study were (1) to examine the chronic effects of Lobex on plasma PRL levels in conscious rats and (2) to determine whether the absence of input from the posterior pituitary interferes with estrous cyclicity. Lobex or sham lobectomy were performed under Brevital anesthesia in estrous rats. Blood was collected from a jugular cannula at hourly intervals on the day of surgery and at 09.00, 13.00, and 17.00 h during the following 4 days. Daily water consumption and vaginal cyclicity were monitored for 14 and 20 days, respectively. Within 2 h after Lobex, the plasma PRL levels rose 3- to 4-fold and remained elevated for 3 days before declining to near control levels on the 4th day. None of the Lobex rats resumed cyclicity within 3–4 days, 50% had an interruption of cyclicity for 4–10 days, and the remainder were noncyclic for more than 11 days. Upon resumption of cyclicity, Lobex rats had 11.3 ± 0.4 oviductal ova which is within the normal range for intact ovulating rats. In contrast, 60% of the sham-operated rats resumed cyclicity within 4 days with an afternoon proestrous surge of PRL, whereas 30% became pseudopregnant, as judged by diurnal peaks of plasma PRL levels and a sustained leukocyte smear for 11–13 days. The daily water consumption of Lobex rats was 3-fold higher than that of sham-lobectomized rats for at least 2 weeks. It is concluded that: (1) Lobex results in a prolonged elevation of plasma PRL levels in conscious rats; (2) the eventual decline in plasma PRL is more likely due to a compensatory activation of the hypothalamic dopaminergic system by the Lobex-induced rise in plasma PRL than to a regeneration of the posterior lobe or restoration of its function; (3) the Lobex-induced PRL rise appears to be the cause of interruption of cyclicity, and (4) the data are consistent with the hypothesis that the dopaminergic inhibition of PRL secretion involves two interdependent systems: one consists of the hypothalamus – long portal vessels – and the second comprises of the posterior pituitary -short portal vessels. Depending upon the endocrine conditions and the nature of hormonal or neuronal stimuli, either one or both systems may be activated.

show abstract

“…Kanematsu & Sawyer (1973) showed elevated plasma PRL levels after the hypophyseal stalk was transected in the rat. These results showed that the neuroendocrine control of the pituitary hormones from the hypothalamus via the pituitary-portal system were dominantly controlled by stimulators, with the exception of PRL, which was regulated negatively by dopamine (Harris & Jacobsohn 1950, 1952, MacLeod 1969, Kanematsu & Sawyer 1973. Additionally, neuroendocrinological control of gonadotropin from the hypothalamus is maintained primarily via the stimulation associated with GnRH.…”

Section: Discussionmentioning

confidence: 95%

Hypophysiotropic role of RFamide-related peptide-3 in the inhibition of LH secretion in female rats

Murakami¹,

Matsuzaki²,

Iwasa³

et al. 2008

Journal of Endocrinology

222

174

View full text Add to dashboard Cite

Gonadotropin-inhibitory hormone (GnIH), a newly discovered hypothalamic RFamide peptide, inhibits reproductive activity by decreasing gonadotropin synthesis and release in birds. The gene of the mammalian RFamide-related peptides (RFRP) is orthologous to the GnIH gene. This Rfrp gene gives rise to the two biologically active peptides RFRP-1 (NPSF) and RFRP-3 (NPVF), and i.c.v. injections of RFRP-3 suppress LH secretion in several mammalian species. In this study, we show whether RFRP-3 affects LH secretion at the pituitary level and/or via the release of GnRH at the hypothalamus in mammals. To investigate the suppressive effects of RFRP-3 on the mean level of LH secretion and the frequency of pulsatile LH secretion in vivo, ovariectomized (OVX) mature rats were administered RFRP-3 using either i.c.v. or i.v. injections. Furthermore, the effect of RFRP-3 on LH secretion was also investigated using cultured female rat pituitary cells. With i.v. administrations, RFRP-3 significantly reduced plasma LH concentrations when compared with the physiological saline group. However, after i.c.v. RFRP-3 injections, neither the mean level of LH concentrations nor the frequency of the pulsatile LH secretion was affected. When using cultured pituitary cells, in the absence of GnRH, the suppressive effect of RFRP-3 on LH secretion was not clear, but when GnRH was present, RFRP-3 significantly suppressed LH secretion. These results suggest that RFRP-3 does not affect LH secretion via the release of GnRH, and that RFRP-3 directly acts upon the pituitary to suppress GnRH-stimulated LH secretion in female rats.

show abstract

Elevation of Plasma Prolactin After Hypophysial Stalk Section in the Rat1

Cited by 41 publications

References 0 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

Chronic Posterior Pituitary Lobectomy: Prolonged Elevation of Plasma Prolactin and Interruption of Cyclicity

Hypophysiotropic role of RFamide-related peptide-3 in the inhibition of LH secretion in female rats

Contact Info

Product

Resources

About