1. Rats housed individually in glass metabolism cages develop hypertension. Since previous experiments have provided some evidence for the involvement of the sympathetic nervous system in the maintenance of the hypertension, the present work was designed to explore the possible involvement of the sympathetic nervous system in the genesis of isolation-induced hypertension.
2. Male and female Wistar rats were treated neonatally with guanethidine, with a protocol designed to produce an extensive peripheral sympathectomy; control rats received saline.
3. The effects of isolation on systolic blood pressure and fluid and electrolyte balances were studied when the rats were mature.
4. Guanethidine-treated rats did not develop hypertension in response to isolation whereas control rats did.
5. There were no significant differences between the fluid and electrolyte balances of the guanethidine-treated rats compared with controls throughout the period of isolation.
6. It is concluded that a fully functional sympathetic nervous system is required for the development of isolation-induced hypertension, but its involvement is not through a modulation of renal function.