Figure 5. Distinct ACP and ACV activation patterns in baroreceptor and dive reflexes.

a, Experimental design for baroreceptor reflex induction. Awake wild-type mice were administered α₁ receptor agonist phenylephrine (PE), which causes peripheral blood vessel vasoconstriction, activating the baroreceptor reflex. After 150 minutes to allow c-Fos expression, mice were euthanized and activity of ACP and ACV neurons analyzed by c-Fos immunostaining. b, Fraction of ACP or ACV neurons positive for c-Fos following vehicle (- PE) or phenylephrine (+ PE) injections (n = 4 mice per condition, 418 total scored neurons). ACP: p = 0.4, ACV: p < 0.0001. c, Immunostaining for c-Fos in ACP neurons (Calbindin+, white arrowheads) in rostral Amb following baroreflex induction as above. Middle panel inset, positive immunostaining control showing c-Fos+ neurons in pre-Bӧtzinger complex of same brain section. d, Immunostaining for c-Fos in ACV neurons (BChE+, red arrowheads) in caudal Amb following baroreflex induction. e, Experimental design for dive reflex induction. Wild-type mice anesthetized with isoflurane received 10 nasal immersions (5–10 sec each) in thermoneutral water over 30 minutes, with ECG recorded to confirm dive reflex activation. Control mice were similarly anesthetized but did not receive immersions. ACP and ACV neurons were immunostained for c-Fos as in a-d. f, Fraction of ACP or ACV neurons that stained positive for c-Fos without (- Dive) or with dive reflex activation (+ Dive) (n = 5 mice per condition, 485 total scored neurons). ACP: p < 0.0001, ACV: p = 0.06. Note robust activation of ACP neurons but limited activation of ACV neurons. g, Immunostaining for c-Fos in ACP neurons (red arrowheads) following dive reflex induction. h, Immunostaining for c-Fos in ACV neurons following dive reflex induction. Note most ACV neurons are c-Fos- (white arrowheads), but rare ACV neurons are c-Fos+ (red arrowhead). Data shown as mean ± S.D. ****: p < 0.0001 by unpaired two-tailed t test. Bars, 20 μm.