Water intake and time course of drinking after single or repeated chlordiazepoxide injections

It has been shown in male rats of two albino strains, Wistar and Sprague-Dawley, that differences in emotional reactivity were related to physiological differences (Bernet and Denimal, 1978). Particularly the resting heart rate was slower in the more emotionally reactive rats. It has been suggested that emotional reactivity is linked with a certain neurovegetative balance. This possibility was investigated in twelve rats of each strain by means of differential blockade of the autonomic nervous system by atropine and propranolol.The heart rate response of the emotionally reactive strain to propranolol was statistically smaller than that of the non reactive strain. On the other hand, the heart rate increase resulting from atropine treatment was more elevated in the same rats. The calculated sympathetic and parasympathetic tones (as % of intrinsic heart rate) were 8% and 30% respectively in the reactive rats. However, both of the tones were 14% in the non reactive rats. In conclusion, the high defecating rats in the open-field exhibit a lower sympathetic tone linked with a higher parasympathetic tone.