Evidence That Hypothalamic RFamide Related Peptide-3 Neurones are not Leptin-Responsive in Mice and Rats

• Published in: Journal of neuroendocrinology Vol. 26; no. 4; pp. 247 - 257
• Main Authors: Rizwan, M. Z., Harbid, A. A., Inglis, M. A., Quennell, J. H., Anderson, G. M.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.04.2014; Wiley Subscription Services, Inc
• Subjects: Animals; Base Sequence; DNA Primers; GnIH; GnRH; Hypothalamic Hormones - genetics; Hypothalamic Hormones - physiology; Hypothalamus - cytology; leptin; Leptin - physiology; Mice; Mice, Inbred Strains; Neurons - physiology; Neuropeptides - physiology; Polymerase Chain Reaction; Rats; RFamide related peptide-3; RNA, Messenger - genetics; GnRH; RFamide related peptide-3; leptin; GnIH
• ISSN: 0953-8194; 1365-2826
• DOI: 10.1111/jne.12140

Leptin, a permissive hormonal regulator of fertility, provides information about the body's energy reserves to the hypothalamic gonadotrophin‐releasing hormone (GnRH) neuronal system that drives reproduction. Leptin does not directly act on GnRH neurones, and the neuronal pathways that it uses remain unclear. RFamide‐related peptide‐3 (RFRP‐3) neurones project to GnRH neurones and primarily inhibit their activity. We tested whether leptin could act via RFRP‐3 neurones to potentially modulate GnRH activity. First, the effects of leptin deficiency or high‐fat diet‐induced obesity on RFRP‐3 cell numbers and gene expression were assessed in male and female mice. There was no significant difference in Rfrp mRNA levels or RFRP‐3‐immunoreactive cell counts in wild‐type versus leptin‐deficient ob/ob animals, or in low‐fat versus high‐fat diet fed wild‐type mice. Second, the presence of leptin‐induced signalling in RFRP‐3 neurones was examined in male and female wild‐type mice and rats. Dual label immunohistochemistry revealed leptin‐induced phosphorylated signal transducer and activator of transcription‐3 in close proximity to RFRP‐3 neurones, although there was very little (2–13%) colocalisation and no significant differences between vehicle and leptin‐treated animals. Furthermore, we were unable to detect leptin receptor mRNA in a semi‐purified RFRP‐3 cell preparation. Because GABA neurones form critical leptin‐responsive GnRH inputs, we also determined whether RFRP‐3 and GABA cells were colocalised. No such colocalisation was detected. These results support the concept that leptin has little or no effects on RFRP‐3 neurones, and that these neurones are unlikely to be an important neuronal pathway for the metabolic regulation of fertility by leptin.