The bed nucleus is a neuroanatomical substrate for the anorectic effect of corticotropin-releasing factor and for its reversal by nociceptin/orphanin FQ

Abstract

Nociceptin/orphanin FQ (N/OFQ), the endogenous ligand of the opioid N/OFQ receptor (NOP), possesses marked functional anti-stress and anti-corticotropin-releasing factor (CRF) actions. We have shown that intracerebroventricular injection of N/OFQ reverses the hypophagic effect induced by stress or by CRF given intracerebroventricularly. To shed new light on the mechanisms involved in the anti-CRF action of N/OFQ, we investigated the ability of N/OFQ to prevent CRF-induced anorexia after microinjection studies into brain areas of potential interest in the control of feeding behavior and coexpressing NOP and CRF receptors. These areas include the bed nucleus of the stria terminalis (BNST), the central amygdala (CeA), the locus ceruleus (LC), the ventromedial hypothalamus (VMH), the paraventricular nucleus (PVN), and the dorsal raphe (DR). The results demonstrated that the anorectic effect of 0.04 nmol of CRF per rat (200 ng per rat) given intracerebroventricularly is reversed by pretreatment with 0.01-0.21 nmol of N/OFQ per rat (25-500 ng per rat) injected into the BNST but not into the CeA, LC, VMH, PVN, or DR. Microinjection of 0.01-0.02 nmol of CRF per site (50-100 ng per site) into the BNST but not into the CeA or the LC induced marked anorexia in food-deprived rats. Pretreatment with 0.01-0.21 nmol of N/OFQ per site (25-500 ng per site) into the BNST also blocked the anorectic action of 0.02 nmol of CRF per site (100 ng per site) given in the same area. Finally, intra-BNST microinjection of 0.01-0.21 nmol of N/OFQ per site (25-500 ng per site) did not modify food intake in either food-sated or food-deprived rats. These data demonstrate that the BNST is involved in the modulation of CRF-induced anorexia, which is prevented by activation of N/OFQ receptors.

Figure 1.

Histological reconstruction showing correct (filled circles) and incorrect (filled triangles) placements of cannula tips. Data presented in the figure are representative of only some of the animals used in the study and are indicative of the criteria used for identification of the correct injection sites. Drawing is from the atlas of Paxinos and Watson (1986).

Figure 2.

Effect of intracerebroventricular (ICV) CRF on food intake in rats deprived of food for 20 hr. Rats (n = 8) were injected intracerebroventricularly with 0.02, 0.04, 0.1, or 0.21 nmol of CRF or its vehicle (Veh) per rat. Access to food was given 20 min after CRF administration, and food intake was measured after 30 and 60 min. ^**p < 0.01 versus control (Veh). Error bars represent SEM.

Figure 3.

Effect of direct microinjections of N/OFQ in discrete brain areas on the inhibition of food intake after intracerebroventricular CRF administration in rats deprived of food for 20 hr. A, BNST of rats (n = 9) was injected with 0.01, 0.02, or 0.21 nmol of N/OFQ or its vehicle (Veh) per site 10 min before injection of 0.04 nmol of CRF or its vehicle per rat intracerebroventricularly. CeA (B; n = 8 rats), LC (C; n = 8 rats), VMH (D; n = 8 rats), PVN (E; n = 8 rats), and DR (F; n = 10) were injected with 0.01, 0.02, or 0.21 nmol of N/OFQ or its vehicle per site 10 min before 0.04 nmol of CRF or its vehicle per rat. Access to food was given 20 min after CRF administration, and food intake was measured after 30 and 60 min. ^**p < 0.01 versus control (Veh + Veh). Error bars represent SEM.

Figure 4.

Effect of direct microinjections of CRF in discrete brain areas on food intake in rats deprived of food for 20 hr. BNSTs (A; n = 8 rats), CeAs (B; n = 7 rats), and LCs (C; n = 7 rats) were injected with 0.01 or 0.02 nmol of CRF or its vehicle (Veh) per site. Access to food was given 20 min after CRF administration, and food intake was measured after 30 and 60 min. ^**p < 0.01 versus control (Veh). Error bars represent SEM.

Figure 5.

Effect of direct microinjections of N/OFQ and CRF into the BNST on food intake in rats deprived of food for 20 hr. BNSTs of rats (n = 6) were injected first with 0.01, 0.02, or 0.21 nmol of N/OFQ or its vehicle (Veh) per site. After 10 min, animals received an intra-BNST injection of 0.02 nmol of CRF or its vehicle per site. Access to food was given 20 min after CRF administration, and food intake was measured after 30 and 60 min. ^*p < 0.05 and ^**p < 0.01 versus control (Veh + Veh). Error bars represent SEM.