Nociceptin/orphanin FQ (N/OFQ) has been shown to produce hyperphagia when injected into the brain of normal rats. Rats with the metabolic syndrome, such as the WOKW rats, exibit lower hyperphagic effects following central injection of N/OFQ when compared to lean counterparts such as the dark agouti (DA) rats. Crossing between WOKW and DA rats has generated several congenic lines of rats the chromosomal differences of which have been fully characterized. DA.WOKW rats were the offspring of a cross of WOKW and DA rats using marker-aided selection. The resulting cross hybrids were repeatedly backcrossed with DA using animals which were heterozygous at loci D3Mgh5, D3Rat1 (DA.3Wa) or D3Mit10, D3Rat189 (DA.3Wb) or D5Mgh6, D5Mit5 (DA.5W) or D9Mgh1, D16Rat89 (DA.16W) and were most homozygous for DA alleles at 180 background loci. After 5 backcross generations, the animals were inter-crossed. Animals homozygous for WOKW alleles at the loci of interest were selected and the congenic DA.3Wa, DA.3Wb, DA.5W and DA.16W rat strains were founded. Founder animals were fine mapped with more than 30 polymorphic markers on chromosomes 3, 5, and 16, chromosomes very important in the expression of diabetes and obesity.The present work evaluated the hyperphagic effect of N/OFQ in all these lines and the location of NOP receptor and N/OFQ into the hypothalamus of WOKW and DA rats using immunohistochemistry. Six males of each congenic strain and DA as well as WOKW rats were injected into the lateral brain ventricle with N/OFQ (2.1, 4.2, 8.4 nmol/rat) and their feeding responses were measured for the following 2h. DA, DA.5W, DA.3Wb significantly dose-dependently increased their food intake after N/OFQ injection. On the other hand, WOKW, and DA.16W rats did not show any significant increase in food intake. Immunoreactivity to N/OFQ was seen in the arcuate nucleus, ventromedial nucleus and dorsomedial nucleus. Staining was intense and present in both neurons and fibers. NOP receptor immunoreactivity was found in fibers only. Staining was low to moderate in ventromedial nucleus and dorsomedial nucleus, and strongly positive in the median eminence. No significant differences emerged by comparing WOKW and DA rats.The exchange of a region on chromosomes 3b and 5, but not in chromosome 16 significantly produced alteration of feeding in these animals. Therefore, these resistant WOKW and chromosome 16 congenic animals could help to identify the genes controlling N/OFQ-induced hyperphagia.
The hyperphagic effects of Nociceptin/Orfanin FQ (N/OFQ) in obese and lean rats and their congenic offspring: relation to expression of N/OFQ-NOP receptors in the hypothalamus and their genoma
CIFANI, Carlo;MASSI, Maurizio;POLIDORI, Carlo
2008-01-01
Abstract
Nociceptin/orphanin FQ (N/OFQ) has been shown to produce hyperphagia when injected into the brain of normal rats. Rats with the metabolic syndrome, such as the WOKW rats, exibit lower hyperphagic effects following central injection of N/OFQ when compared to lean counterparts such as the dark agouti (DA) rats. Crossing between WOKW and DA rats has generated several congenic lines of rats the chromosomal differences of which have been fully characterized. DA.WOKW rats were the offspring of a cross of WOKW and DA rats using marker-aided selection. The resulting cross hybrids were repeatedly backcrossed with DA using animals which were heterozygous at loci D3Mgh5, D3Rat1 (DA.3Wa) or D3Mit10, D3Rat189 (DA.3Wb) or D5Mgh6, D5Mit5 (DA.5W) or D9Mgh1, D16Rat89 (DA.16W) and were most homozygous for DA alleles at 180 background loci. After 5 backcross generations, the animals were inter-crossed. Animals homozygous for WOKW alleles at the loci of interest were selected and the congenic DA.3Wa, DA.3Wb, DA.5W and DA.16W rat strains were founded. Founder animals were fine mapped with more than 30 polymorphic markers on chromosomes 3, 5, and 16, chromosomes very important in the expression of diabetes and obesity.The present work evaluated the hyperphagic effect of N/OFQ in all these lines and the location of NOP receptor and N/OFQ into the hypothalamus of WOKW and DA rats using immunohistochemistry. Six males of each congenic strain and DA as well as WOKW rats were injected into the lateral brain ventricle with N/OFQ (2.1, 4.2, 8.4 nmol/rat) and their feeding responses were measured for the following 2h. DA, DA.5W, DA.3Wb significantly dose-dependently increased their food intake after N/OFQ injection. On the other hand, WOKW, and DA.16W rats did not show any significant increase in food intake. Immunoreactivity to N/OFQ was seen in the arcuate nucleus, ventromedial nucleus and dorsomedial nucleus. Staining was intense and present in both neurons and fibers. NOP receptor immunoreactivity was found in fibers only. Staining was low to moderate in ventromedial nucleus and dorsomedial nucleus, and strongly positive in the median eminence. No significant differences emerged by comparing WOKW and DA rats.The exchange of a region on chromosomes 3b and 5, but not in chromosome 16 significantly produced alteration of feeding in these animals. Therefore, these resistant WOKW and chromosome 16 congenic animals could help to identify the genes controlling N/OFQ-induced hyperphagia.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.