Ageing and the Diurnal Expression of mRNAs for Vasoactive Intestinal Peptide and for the VPAC2 and PAC1 Receptors in the Suprachiasmatic Nucleus of Male Rats

Vasoactive intestinal peptide (VIP) is present in thyroid parasympathetic nerves. To assess the involvement of endogenous VIP in the regulation of thyroid function, blood levels of thyroid hormones and thyroid blood flows (TBF) were measured after systemic immunization against VIP or after transection of the superior laryngeal nerves in male rats, which reduced the thyroid content of VIP but did not affect blood levels of thyroid hormones or TBF. Anti-VIP monoclonal antibody or anti-VIP serum was used for immunization against VIP in normal rats. In addition, VIP antibody was given to rats fed an iodine-deficient diet for 5 days to examine the involvement of this peptide in iodine deficiency-induced increases in TBF. Effects were measured at different times (90 s, 30 min, 1 h, and 5 days) after immunoneutralization, but none of these treatments changed blood levels of thyroid hormones or TBF in normal or iodine-deficient rats. However, passive immunization against VIP was associated with a high binding capacity of rat plasma to VIP, and this treatment reduced blood levels of prolactin as well as blood flows to the duodenum, stomach, and lung. These findings suggest that the VIP present in thyroid nerves is not involved in maintaining basal thyroid hormone secretion or TBF and that this neuropeptide does not mediate thyroid vascular adjustments to dietary iodine deficiency.

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Catecholaminergic innervation of the suprachiasmatic nucleus in the adult rat: ultrastructural relationships with neurons containing vasoactive intestinal peptide or vasopressin

Cell and Tissue Research ◽

10.1007/s004410050333 ◽

1995 ◽

Vol 280 (1) ◽

pp. 87-96

Author(s):

H�l�ne Jacomy ◽

Olivier Bosler

Keyword(s):

Vasoactive Intestinal Peptide ◽

Suprachiasmatic Nucleus ◽

Adult Rat ◽

Catecholaminergic Innervation

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Vasoactive Intestinal Peptide Modulation of the Steroid-Induced LH Surge Involves Kisspeptin Signaling in Young but Not in Middle-Aged Female Rats

Endocrinology ◽

10.1210/en.2013-1793 ◽

2014 ◽

Vol 155 (6) ◽

pp. 2222-2232 ◽

Cited By ~ 10

Author(s):

Alexander S. Kauffman ◽

Yan Sun ◽

Joshua Kim ◽

Azim R. Khan ◽

Jun Shu ◽

...

Keyword(s):

Vasoactive Intestinal Peptide ◽

Suprachiasmatic Nucleus ◽

Reproductive Age ◽

Female Rats ◽

Mrna Levels ◽

Dependent Manner ◽

Middle Aged ◽

Lh Surge ◽

Young Females ◽

Gnrh Neurons

Age-related LH surge dysfunction in middle-aged rats is characterized, in part, by reduced responsiveness to estradiol (E2)-positive feedback and reduced hypothalamic kisspeptin neurotransmission. Vasoactive intestinal peptide (VIP) neurons in the suprachiasmatic nucleus project to hypothalamic regions that house kisspeptin neurons. Additionally, middle-age females express less VIP mRNA in the suprachiasmatic nucleus on the day of the LH surge and intracerebroventricular (icv) VIP infusion restores LH surges. We tested the hypothesis that icv infusion of VIP modulates the LH surge through effects on the kisspeptin and RFamide-related peptide-3 (RFRP-3; an estradiol-regulated inhibitor of GnRH neurons) neurotransmitter systems. Brains were collected for in situ hybridization analyses from ovariectomized and ovarian hormone-primed young and middle-aged females infused with VIP or saline. The percentage of GnRH and Kiss1 cells coexpressing cfos and total Kiss1 mRNA were reduced in saline-infused middle-aged compared with young females. In young females, VIP reduced the percentage of GnRH and Kiss1 cells coexpressing cfos, suggesting that increased VIP signaling in young females adversely affected the function of Kiss1 and GnRH neurons. In middle-aged females, VIP increased the percentage of GnRH but not Kiss1 neurons coexpressing cfos, suggesting VIP affects LH release in middle-aged females through kisspeptin-independent effects on GnRH neurons. Neither reproductive age nor VIP affected Rfrp cell number, Rfrp mRNA levels per cell, or coexpression of cfos in Rfrp cells. These data suggest that VIP differentially affects activation of GnRH and kisspeptin neurons of female rats in an age-dependent manner.

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