Forebrain injections of nociceptin / orphanin FQ (N/OFQ), the endogenous ligand of the NOP opioid receptor, previously referred to as 1 ORL1 or OP4 receptor, stimulate feeding in freely feeding rats, while the NOP receptor antagonist [Nphe ]N/OFQ(1-13)NH inhibits 2 food deprivation-induced feeding. To further evaluate whether the N/OFQ-NOP receptor system plays a physiological role in feeding control, the present study evaluated forebrain mRNA levels for the N/OFQ precursor (pro-N/OFQ), as well as for the NOP receptor in food deprived rats. The results obtained show that food deprived rats have lower mRNA levels for the NOP receptor in several forebrain regions; a significant reduction was found in the paraventricular and lateral hypothalamic nuclei and in the central nucleus of the amygdala. Food deprived rats also exhibited lower pro-N/OFQ mRNA levels in the central amygdala. These results suggest that the N/OFQ-NOP receptor system may have a physiological role in feeding control. The observation that food deprivation reduces gene expression of the N/OFQ-NOP receptor system is apparently not consistent with a direct hyperphagic action for N/OFQ. Taking into account that N/OFQ exerts inhibitory actions at cellular level, the present results may be in keeping with the hypothesis that N/OFQ stimulates feeding by inhibiting neurons inhibitory for food intake; under conditions of food deprivation, these neurons may be silent and the N/OFQ-NOP receptor system, which controls them, may also be regulated at a lower level. Consistently, in the present study N/OFQ stimulated food intake in freely feeding rats, but did not further increase feeding in food deprived rats.

Pro-nociceptin/orphanin FQ and NOP receptor mRNA levels in the forebrain of food deprived rats

RODI, Donata;BREGOLA, Gianni;ZUCCHINI, Silvia;SIMONATO, Michele;
2002

Abstract

Forebrain injections of nociceptin / orphanin FQ (N/OFQ), the endogenous ligand of the NOP opioid receptor, previously referred to as 1 ORL1 or OP4 receptor, stimulate feeding in freely feeding rats, while the NOP receptor antagonist [Nphe ]N/OFQ(1-13)NH inhibits 2 food deprivation-induced feeding. To further evaluate whether the N/OFQ-NOP receptor system plays a physiological role in feeding control, the present study evaluated forebrain mRNA levels for the N/OFQ precursor (pro-N/OFQ), as well as for the NOP receptor in food deprived rats. The results obtained show that food deprived rats have lower mRNA levels for the NOP receptor in several forebrain regions; a significant reduction was found in the paraventricular and lateral hypothalamic nuclei and in the central nucleus of the amygdala. Food deprived rats also exhibited lower pro-N/OFQ mRNA levels in the central amygdala. These results suggest that the N/OFQ-NOP receptor system may have a physiological role in feeding control. The observation that food deprivation reduces gene expression of the N/OFQ-NOP receptor system is apparently not consistent with a direct hyperphagic action for N/OFQ. Taking into account that N/OFQ exerts inhibitory actions at cellular level, the present results may be in keeping with the hypothesis that N/OFQ stimulates feeding by inhibiting neurons inhibitory for food intake; under conditions of food deprivation, these neurons may be silent and the N/OFQ-NOP receptor system, which controls them, may also be regulated at a lower level. Consistently, in the present study N/OFQ stimulated food intake in freely feeding rats, but did not further increase feeding in food deprived rats.
2002
Rodi, Donata; Polidori, C; Bregola, Gianni; Zucchini, Silvia; Simonato, Michele; Massi, M.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/1207817
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