January 1, 2000Open Access

Integration of Aortic Nerve Inputs in Hypertensive Rats

Q: What is the clinical evidence from this study?

Study design: Other. Population: Renal wrap hypertension. Intervention: Renal wrap hypertension vs. Normotensive rats. Primary outcome: Aortic nerve (AN)-evoked depressor responses and integration of baroreceptor inputs within the nucleus of the solitary tract (p=<0.05).

Key Result

Renal wrap hypertension in rats is associated with reduced aortic nerve-evoked depressor responses and altered integration of afferent inputs within the nucleus of the solitary tract (P<0.05).

PICO

Population

Anesthetized and paralyzed renal wrap hypertensive and normotensive rats.

Exposure / Comparator

Renal wrap hypertension vs Normotensive rats

Primary Outcome

Aortic nerve (AN)-evoked depressor responses and integration of baroreceptor inputs within the nucleus of the solitary tract, p=<0.05

Main Result

p-value: p=<0.05

Abstract

The integration of arterial baroreceptor afferent inputs was studied in renal wrap hypertensive (HT) and normotensive (NT) rats. In anesthetized and paralyzed rats, aortic nerve (AN)-evoked depressor responses were reduced in HT compared with NT rats (P<0.05). We tested the hypothesis that the attenuated baroreflex was associated with altered integration of baroreceptor inputs within the nucleus of the solitary tract. Based on onset latency and the ability of monosynaptic neurons (MSNs) to respond to each of 2 AN stimuli separated by 5 ms, cells in HT and NT rats were divided into 3 groups: short-latency MSNs (SLMSNs), long-latency MSNs (LLMSNs), and polysynaptic neurons (PSNs). A higher percentage of PSNs (73% versus 61%) and a lower percentage of SLMSNs (20% versus 27%) or LLMSNs (7% versus 12%) were found in HT rats (P<0.05). In addition, in HT compared with NT rats, the AN onset latency was greater in PSNs (29. 9+/-1.1 versus 26.7+/-0.8 ms) but not in SLMSNs (5.0+/-0.5 versus 5. 0+/-0.3 ms) or LLMSNs (22.9+/-1.2 versus 24.1+/-0.7 ms) (P<0.05). Finally, in HT compared with NT rats, the number of PSNs responding to a single AN stimulus with multiple action potentials was increased (40% versus 19%) (P<0.05). This was not observed in SLMSNs (26% versus 13%) or LLMSNs (12% versus 18%). The results indicate that renal wrap hypertension is associated with reduced AN-evoked depressor responses. There also were alterations in the integration of AN afferent inputs within the nucleus of the solitary tract, and these alterations were most marked in the PSN population.