[Effects of left atrial stretch and carotid occlusion on the single unit activity of anterior and posterior hypothalamus in cat].

The effects of left atrial stretch (AS) and carotid occlusion (CO) on the single unit activity of anterior and posterior hypothalamus (AH and PH) were investigated in 40 urethan-chloralose-anesthetized cats. A total of 185 units with spontaneous discharge were recorded. 46.3% (44/95) of the neurons in AH and 23.3% (21/90) of those in PH were responsive to AS. Majority of the neurons affected by AS exhibited a decrease in firing rate. A few units only showed transient response during the onset and release of AS (on-off response). Out of the 185 units, 85 units were tested by both AS and CO, and 15 units (17.6%) were responsive to both interventions. Among them 11 (73.7%) were inhibited by AS and excited by CO. From the results mentioned above, it is suggested that: (1) AS may exert an inhibitory effect on the activity of neurons in AH. (2) The activity of neurons in PH may be also affected by AS. (3) The inputs from the atrial volume receptor and carotid baroreceptor converge on the same neuron of the hypothalamus.