348 p. TEITELBAUM AND A. N. EPSTEIN 



and glossopharyngeal nerves to diminish the sense of taste, and also re- 

 moved the olfactory bulbs to eliminate smell. They showed that none of 

 these removals had any effect on thirst or the regulation of water intake. 

 Since they mentioned no feeding aberrations, we may assume that the 

 regulation of food intake was likewise undisturbed. 



However, as Richter (1956) has pointed out, it is extremely difficult to 

 achieve complete surgical denervation of taste. In the rat, he found taste 

 buds present even after combined section of the chorda tympani, glosso- 

 pharyngeal, and the pharyngeal branch of the vagus. Pfaffmann (1952) 

 has shown that only partial loss of taste results from combined removal of 

 the chorda tympani and glossopharyngeal nerves. When the pharyngeal 

 branch of the vagus is also removed, severe impairment of chewing and 

 swallowing can result, with complications arising from the aspiration of 

 food during feeding. Our own attempts at removals have verified Pfaff- 

 mann's findings. Other workers have attempted to destroy the sense of 

 taste by ablations in the central nervous system. Cortical removal of the 

 projection areas yield only a partial loss of taste sensitivity with consider- 

 able recovery of function (Benjamin and Pfaffmann, 1955 ; Bagshaw and 

 Pribram, 1953), and even by destroying the thalamic nuclei projecting to 

 the taste areas, it is difiicult to completely remove the sense of taste (Abies 

 and Benjamin, 1960 ; Oakley and Pfaffmann, 1962 ; Andersson and 

 Jewell, 1957). 



We have, therefore, turned to an alternate method of removing the in- 

 fluence of taste and smell from the regulation of food and water intake. 

 Epstein (1960) has devised a permanently implanted gastric tube for the 

 rat that does not require the use of gastrointestinal surgery and does not 

 interfere with the animal's normal feeding and drinking. The chronic 

 stomach tube is shown in Fig. 1. 



A slender polyethylene tube is slipped into the rat's nostril, through the 

 nasopharynx, into the esophagus, and down into the stomach. The outer 

 end of the tube is brought under the skin of the snout and scalp to the top 

 of the skull where it is anchored firmly and permanently by screws and 

 dental cement. Water or liquid food can now be pumped directly into the 

 animal's stomach, thus completely by-passing the nasal and oro-pharyngeal 

 receptors for taste and smell. By training the rat to press a lever to inject 

 water or a liquid diet directly into its own stomach, we can study the regu- 

 lation of food and water intake in the absence of all oro-pharyngeal sensa- 

 tions, particularly taste and smell, and without even the consummatory 

 acts of chewing or swallowing. This arrangement is shown in Fig. 2. 



The rat is first taught to press a bar for the delivery of fluid into a cup in 

 its cage. It ingests the fluid by mouth. Then the pump is connected to 

 the animal's gastric tube so that when the animal presses the bar, it delivers 

 food or water directly into its own stomach. A watertight swivel joint 



