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ABSTRACT: It is well established that testosterone and neuropeptide Y (NPY), via its Y1 receptor (Y1R), are involved in the central control of the gonadotrope axis in male rats. Here we examined if a similar interaction also occurs in the male peripheral reproductive target organ, the testes. Expression of the Y1R transcript and protein and changes in testicular microcirculation were studied in normal rats and 12 days following hypophysectomy with and without testosterone substitution (1 or 25 mg s.c.). In situ hybridization and immunohistochemistry showed strong expression of, respectively, Y1R messenger RNA (Y1R mRNA) and Y1R-like immunoreactivity (Y1R-LI) in vascular smooth muscles in the testes of control and hypophysectomized rats treated with testosterone, but was not seen without testosterone substitution. In parallel, control animals and hypophysectomized, testosterone-supplemented rats showed a strong (approximately 40%) decrease in testicular blood flow following intratesticular (i.t.) injection of the Y1-R agonists, [Leu(31), Pro(34)]NPY, [D-Arg(25)]NPY or NPY, an effect which was completely blocked by prior intravenous administration of the Y1R antagonist, BIBP3226. No significant change in testicular blood flow following i.t. injection of NPY was seen in hypophysectomized rats without testosterone substitution. These findings suggest that the high levels of Y1R mRNA and Y1R-LI in the testes reflect expression of functional Y1Rs mediating vasoconstriction, and that testosterone regulates expression of functional Y1Rs.
Neuroendocrinology 07/2008; 88(3):216-26. · 2.38 Impact Factor
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ABSTRACT: Neuropeptide Y (NPY) neurons abundantly innervate the hypothalamus, where NPY is involved in the regulation and integration of a broad range of homeostatic functions. In order to understand NPY-mediated behavioral, autonomic and neuroendocrine effects, it is important to characterize in detail the distribution of the hypothalamic NPY receptors. In this review, we briefly summarize the origin of NPY and its two related peptides, peptide YY and pancreatic polypeptide in the hypothalamus. Moreover, based on the results obtained with histological techniques such as in situ hybridization, immunohistochemistry and ligand binding, we summarize data on the hypothalamic distribution of the known NPY receptors, the Y1 Y2, Y4 and Y5 receptors as best characterized to date. These NPY receptors are found with individual distribution patterns in many hypothalamic neurons including neuroendocrine motoneurons, magnocellular neurosecretory neurons and numerous neurons connecting the hypothalamus with the limbic and the autonomic nervous systems. The histochemical analyses allow characterization of coexisting molecules and in this way definition of the neurochemistry of NPY circuitries. By showing coexistence of various NPY receptors they provide a morphological basis for in vitro studies showing heterodimerization of NPY receptors. The NPY neurons and their circuitries underlie the integrative role of NPY as a pleiotropic neuropeptide in the regulation of homeostasis.
Neuropeptides 09/2004; 38(4):175-88. · 1.55 Impact Factor
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ABSTRACT: Using a sensitive immunohistochemical technique, the localization of neuropeptide Y (NPY) Y1-receptor (Y1R)-like immunoreactivity (LI) was studied in various peripheral tissues of rat. Wild-type (WT) and Y1R-knockout (KO) mice were also analyzed. Y1R-LI was found in small arteries and arterioles in many tissues, with particularly high levels in the thyroid and parathyroid glands. In the thyroid gland, Y1R-LI was seen in blood vessel walls lacking alpha-smooth muscle actin, i.e., perhaps in endothelial cells of capillaries. Larger arteries lacked detectable Y1R-LI. A distinct Y1R-immunoreactive (IR) reticulum was seen in the WT mouse spleen, but not in Y1R-KO mouse or rat. In the gastrointestinal tract, Y1R-positive neurons were observed in the myenteric plexus, and a few enteroendocrine cells were Y1R-IR. Some cells in islets of Langerhans in the pancreas were Y1R-positive, and double immunostaining showed coexistence with somatostatin in D-cells. In the urogenital tract, Y1R-LI was observed in the collecting tubule cells of the renal papillae and in some epithelial cells of the seminal vesicle. Some chromaffin cells of adrenal medulla were positive for Y1R. The problem of the specificity of the Y1R-LI is evaluated using adsorption tests as well as comparisons among rat, WT mouse, and mouse with deleted Y1R. Our findings support many earlier studies based on other methodologies, showing that Y1Rs on smooth muscle cells of blood vessels mediate NPY-induced vasoconstriction in various organs. In addition, Y1Rs in other cells in parenchymal tissues of several organs suggest nonvascular effects of NPY via the Y1R.
The Journal of Comparative Neurology 09/2002; 449(4):390-404. · 3.81 Impact Factor
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ABSTRACT: Using a sensitive immunohistochemical method, the localization of the neuropeptide Y (NPY) Y1 receptor (Y1R) was studied in contralateral and ipsilateral dorsal root ganglion (DRG) neurons of rats subjected to different unilateral manipulations with focus on their axonal processes and projection areas. Y1R-like immunoreactivity (LI) was observed in the contralateral sciatic nerve and dorsal roots of lesioned rats, and double staining revealed colocalization with calcitonin gene-related peptide (CGRP). Y1R-LI was also seen in fibers close to and even within the epidermis. A fairly small number of nerve endings double-labeled for Y1R and CGRP were present in the dorsal horn. After unilateral crush of the sciatic nerve Y1R- and CGRP-LI accumulated in the same axons proximal to the lesion. After dorsal rhizotomy CGRP-LI was strongly reduced in the ipsilateral dorsal horn. No certain change was observed for Y1R- or NPY-LI, but Y1R/CGRP double-labeled nerve endings disappeared after the lesion. These results strongly suggest centrifugal transport of Y1Rs in DRG neurons, mainly to the peripheral sensory branches. To what extent these Y1Rs are functional has not been analyzed here, but a recent study on Y1R null mice provides evidence for involvement of prejunctional Y1Rs in peripheral sensory functions
Experimental Neurology 04/2002; 174(1):1-10. · 4.70 Impact Factor
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ABSTRACT: Expression of mRNAs for neuropeptide Y (NPY) and its receptor subtypes Y1 (Y1-R), Y2 (Y2-R) and Y5 (Y5-R) was studied in adult rat brain using in situ hybridization after 40 rapidly recurring seizures induced with 5-min interval by hippocampal kindling stimulations. At 2–4 h post-seizure, NPY mRNA levels were markedly elevated in dentate granule cells, CA1 and CA3 pyramidal layers, amygdala and piriform and entorhinal cortices. Gene expression had returned to control level in the dentate granule cell layer at 48 h but remained high in the other areas, reaching baseline at 1 week. Transient decreases of Y1-R mRNA levels were detected at 2–4 h in hippocampal subregions, amygdala, piriform, entorhinal and somatosensory cortices. The Y2-R mRNA levels were reduced at 2–4 h in the CA3 region and piriform cortex, but exhibited marked increases at 48 h and 1 week post-seizure in the dentate gyrus, amygdala and piriform and entorhinal cortices. At 3 weeks, Y2-R mRNA expression had virtually returned to baseline. Elevated Y5-R mRNA levels were only detected at 2–4 h and confined to dentate granule cell layer and piriform and entorhinal cortices. These results demonstrate a cell- and region-specific, differential regulation of mRNA expression for NPY and Y1-R, Y2-R, and Y5-R in the limbic system following recurring seizures. Because the gene changes were transient, it seems unlikely that the presumed alterations of the corresponding proteins are involved in the maintenance of the epileptic syndrome, which develops up to 4 weeks post-seizure in the present model and is stable thereafter. Our data provide further support for the hypothesis that the changes of NPY and its receptors act to dampen seizure susceptibility, and suggest that the cascade of gene changes is orchestrated to optimize this anticonvulsant effect.
Molecular Brain Research 10/1999; · 2.00 Impact Factor
