Effect of oxytocin, prolactin-releasing peptide, or corticotropin-releasing hormone on feeding behavior in steers

As a preliminary step to elucidate the involvement of central neurotransmitters in the dip in voluntary feed intake during the perinatal period in cows, we investigated the effect of intracerebroventricular (ICV) administration of oxytocin, prolactin-releasing peptide (PrRP), or corticotropin-releasing hormone (CRH), the central functions of all of which undergo drastic changes during the perinatal period, on feed intake in steers. Thirty minutes before the onset of feeding, the treatment solution was injected into the third ventricle through an implanted cannula, and feeding-related behaviors were observed for 1 h after the onset of feeding. Neither ICV oxytocin (5 and 50 μg) nor PrRP (2 and 20 nmol) reduced feed intake (n=6). Twenty nanomoles of bovine CRH noticeably inhibited feeding behavior compared with vehicle treatment (n=5, p