Afferent electrical activity of the greater splanchnic and colonic nerves in animals with different degrees of hunger and thirst

Abstract

1. Experiments on 8 dogs with electrodes implanted into the greater splanchnic and colonic nerves showed that with the efferent fibers blocked by cold, potentials can be recorded in these nerves which reflect the state of interoceptors of the internal organs at different levels of hunger and thirst. 2. In animals fed and kept under normal conditions, two types of potentials can be recorded from afferent fibers of the greater splanchnic and colonic nerves: slow (from 15 to 20 msec) low-voltage (up to 15 μv), and fast 5–10 msec) high-voltage (from 15 to 44 μv), clearly grouped in the rhythm of respiration. 3. During deprivation of food or water, the frequency and amplitude of potentials recorded from the greater splanchnic and colonic nerves rises sharply, and the greater the degree of hunger or thirst, the more marked this increase. 4. After feeding of a starving animal, the electrical activity of the greater splanchnic and colonic nerves changes in two phases: it falls in the first 5–10 min, rises again after 40–60 min, and falls again after 3–4 hr. 5. Drinking of water by thirsty animals reduces electrical activity of the afferent fibers of the greater splanchnic and colonic nerves. After sham drinking this decreased activity lasts only for the first 5–10 min, but after natural drinking it persists steadily at this reduced level.