Avian cerebrospinal fluid: repeated collection and testing for a possible role in food intake regulation

A technique for cannulating the Cisterna magna and sampling cerebrospinal fluid from socially housed birds

The measurement of central levels of neurochemicals is an important approach to the understanding of the neurophysiological basis of behavior patterns in animals. Previous studies have utilized central sampling techniques developed for individually housed animals. The purpose of this study was to develop a cannulation technique and a method for sampling cerebrospinal fluid (CSF) from socially housed birds to facilitate the study of the neurophysiological basis of social behaviors. The cannulation technique involved the surgical implantation of a 22-gauge concentric guide cannula into the cisterna magna of 16-wk-old, feed-restricted male broiler breeders (n = 6). Individual-specific coordinates and optimum angle and depth of implantation of the cannula were determined in order to place the cannula correctly in the designated site. Once implanted, the guide cannula proved to be unobtrusive and secure and did not attract aggressive pecking from other birds in the pen. Two methods of CSF sampling were then examined. The first method required the use of a push-pull perfusion pump to withdraw CSF at a rate of 1 to 2 microL/min. The second method (passive), which did not use a pump, involved simply removing a "dummy" cannula from the guide cannula to release the CSF, which was then collected with a glass Hamilton syringe. Samples ranging from 100 to 500 microL were collected using the passive method. The combination of the cannulation technique described and the passive sampling method proved to be the most simple, efficient, and reliable method for measuring central levels of neurochemicals in socially housed broiler breeder males.

[The regulation of feed intake and selection with special reference to poultry]

Feed intake is regulated in a dialogue between the animal and the feed, which is influenced by numerous factors. The hypothalamus has a central integrative function. Furthermore, caudal brain areas (medulla oblongata, pons) are of importance because these areas are relays of peripheral signals and gustatory afferents. All peripheral informations are integrated by various neurotransmitters and neurohormones. The function of this neuronal system is not exactly known yet. Sensorial informations, mechano-, chemo- and osmoreceptors of the gastrointestinal tract and gastrointestinal hormones are discussed as influences of the periphery. The physiological satiety function of cholecystokinin is questionable in poultry. Hepatic chemoreceptors, which are activated by various metabolites, influence the amount of feed ingested. The feed choice appears to be regulated by the same mechanisms. Our knowledge about the translation of peripheral signals into choice behaviour by changes of neurotransmitter systems is limited.