Both corticotropin-releasing factor receptor type 1 and type 2 are involved in stress-induced inhibition of food intake in rats

Rationale Stress-induced inhibition of food intake is reportedly blocked by a selective corticotropin-releasing factor (CRF) type 1 receptor (CRF₁) antagonist, suggesting the involvement of CRF₁ in the inhibitory mechanism. CRF₁ and CRF₂ are considered to function in the inhibition of food intake by CRF-related peptides with different time courses.Objectives This study was designed to clarify whether CRF₂ is also involved in stress-induced inhibition of food intake and to examine the relation of CRF₁ to CRF₂ in the inhibitory mechanism.Methods Antisauvagine-30 (AS-30), a selective CRF₂ antagonist, and/or CRA1000, a selective CRF₁ antagonist, were pre-administered intracerebroventricularly and intraperitoneally, respectively, to male Wistar rats deprived of food for 24 h before the animals were exposed to a 1-h period of stressors and food intake in 1 h after stress exposure was examined. The effect of both antagonists on locomotor activity was also examined.Results Pre-administration of 5–30 g of AS-30 attenuated inhibition of food intake induced by restraint, electric footshock or emotional stress using a communication box. CRA1000 also attenuated the restraint-induced inhibition of food intake at doses of 5 and 10 mg/kg body weight. The reversal of restraint-induced inhibition of food intake by co-administration of AS-30 and CRA1000 was not larger than that by AS-30 or CRA1000 alone. Both antagonists did not affect locomotor activity.Conclusions These results suggest that not only CRF₁, but also CRF₂, are involved in stress-induced inhibition of food intake, and that both subtypes of CRF receptor function probably in series in 1 h after stress exposure.