[Discharges in the white rami communicantes evoked by stimulation of various sections of the hypothalamus].

Electrical responses in L2--L3 white rami on stimulation of anterior and posterior hypothalamus were studied in anesthetized and immobilized cats. The stimulation evoked a complex response consisting of waves I, II, and III with mean latency 19.7 +/- 4.5 msec, 34.0 +/- 5.9 msec, 61.8 +/- 8.7 msec, and 20.5 +/- 6.8 msec, 30.;7 +/- msec, 66.0 +/- 14.9 msec for anterior and posterior hypothalamus respectively. In experiments with simultaneous recording of arterial pressure and hypothalamo-sympathetic discharges, after 10-sec period of tetanic (100/sec) stimulation of the hypothalamus, the early I and early II components were facilitated, while the late component of the hypothalamo-sympathetic discharge was depressed. The duration of this inhibition corresponded to the period of pressure reaction and, therefore, is of baroreceptor origin. Possible mechanisms of hypothalamic regulation of the activity of sympathetic preganglionic neurons are discussed.