Drinking Responses to Intravenous Hypertonic Sodium Chloride Solutions Injected Into Unrestrained Dogs

Abstract

Repeated injections of 20% NaCl solution were made in dogs via a long indwelling venous (polyethylene) catheter. The method obviates restraint and allows continuous access to the drinking pan. More consistent drinking responses were obtained with this technique than with the usual venipuncture method. The response was precise and predictable, especially for the same dog. In a series of 60 experiments on 12 dogs in which 20% NaCl was injected in 5 or 10 cc hourly doses over a 3 to 7 hour period, the average volume of water drunk per cc of 20% NaCl injected was 11.2 cc with a standard deviation of 2.2 cc. The water drunk was sufficient to dilute the NaCl to 1.8% and this occurred despite a 2-fold range in body weight. Each animal showed a characteristic latent period. Three categories of latency, immediate, intermediate, and delayed, were found.