Distribution of hypophysiotropic thyrotropin‐releasing hormone (TRH)‐synthesizing neurons in the hypothalamic paraventricular nucleus of the mouse

Abstract

Hypophysiotropic thyrotropin-releasing hormone (TRH) neurons, the central regulators of the hypothalamus-pituitary-thyroid axis, are located in the hypothalamic paraventricular nucleus (PVN) in a partly overlapping distribution with non-hypophysiotropic TRH neurons. The distribution of hypophysiotropic TRH neurons in the rat PVN is well understood, but the localization of these neurons is unknown in mice. To determine the distribution and phenotype of hypophysiotropic TRH neurons in mice, double- and triple-labeling experiments were performed on sections of intact mice, and mice treated intravenously and intraperitonially with the retrograde tracer Fluoro-Gold. TRH neurons were located in all parts of the PVN except the periventricular zone. Hypophysiotropic TRH neurons were observed only at the mid level of the PVN, primarily in the compact part. In the this part of the PVN, TRH-neurons were intermingled with oxytocin and vasopressin neurons, but based on their size, the TRH neurons were parvocellular and did not contain magnocellular neuropeptides. Co-localization of TRH and CART were observed only in areas where hypophysiotropic TRH neurons were located. In accordance with the morphological observations, hypothyroidism increased TRH mRNA content of neurons only at the mid level of the PVN. These data demonstrate that the distribution of hypophysiotropic TRH neurons in mice is vastly different from the pattern in rats, with a dominant occurrence of these neurosecretory cells in the compact part and adjacent regions at the mid level of the PVN. Furthermore, our data demonstrate that the organization of the PVN is markedly different in mice and rats.

Angiotensin Type-2 Receptors Influence the Activity of Vasopressin Neurons in the Paraventricular Nucleus of the Hypothalamus in Male Mice

“…Additionally, liquid-phase radioimmunoassay (RIA) was used to determine that anti-OT-NP (PS-38) is highly-specific for the OT-NP complex and does not cross-react with AVP-NP, while the anti-AVP-NP (PS-41) reacts with AVP-NP exclusively. Furthermore, as in (21,24), the specificity of the rabbit polyclonal antibody against FluoroGold (FG) was corroborated by the lack of staining on sections originating from mice without FG treatment. Unless otherwise stated, all secondary antibodies were purchased from Jackson Immunoresearch (Westgorve, PA), raised in donkey and used at a 1:500 dilution.…”

“…First, the antibody directed toward GFP, was previously-validated in (12,22), and its specificity was substantiated for the present study by the lack of staining on sections originating from mice that did not express GFP. Next, both anti-OT-NP (PS-38) and anti-AVP-NP (PS-41) were validated in (21,23), in which it was determined these antibodies appropriately and specifically labeled the posterior pituitary, the paraventricular and supraoptic nuclei. Additionally, liquid-phase radioimmunoassay (RIA) was used to determine that anti-OT-NP (PS-38) is highly-specific for the OT-NP complex and does not cross-react with AVP-NP, while the anti-AVP-NP (PS-41) reacts with AVP-NP exclusively.…”

“…All primary antibodies were characterized by the manufacturers and in previously published studies (12,21,22) and are listed in Table 1. First, the antibody directed toward GFP, was previously-validated in (12,22), and its specificity was substantiated for the present study by the lack of staining on sections originating from mice that did not express GFP.…”

Methylation at the CpG island shore region upregulatesNr3c1promoter activity after early-life stress

“…45 The parvocellular division of the PVN harbors distinct sub-populations of peptidergic neurons, among them neurons that express only Crh or Avp, or both. [46][47][48] Here we used triple fluorescence immunohistochemistry to identify which subsets of PVN neurons express GR. GR expression was confined to Crh neurons in control mice and ELS mice, although expression levels were significantly higher in the latter group ( Fig.…”

Regulation of TRH neurons and energy homeostasis-related signals under stress

“…As mentioned, the hypophysiotropic or endocrine cells are concentrated in mid-and caudal-PVN (Simmons & Swanson 2009, Fekete & Lechan 2014. In mouse PVN, 69% of TRHergic endocrine cells project to the median eminence, while 17% project to the neurohypophysis, and the rest are non-endocrine cells localized in the anterior zone (Ghamari-Langroudi et al 2010, Kádár et al 2010). PVN-TRHergic neurons differ not only in their afferents, projections, and receptor expression (Fekete & Lechan 2014) but also according to time of birth; rat non-neuroendocrine neurons peak at embryonic days 11-12 and neuroendocrine neurons at days 12-14 (Markakis & Swanson 1997).…”