PARAVENTRICULAR NUCLEUS CONTRIBUTES TO ACUPUNCTURE MODULATION OF SYMPATHOEXCITATORY CARDIOVASCULAR REFLEXES

Abstract

The paraventricular nucleus (PVN) regulates sympathetic outflow and blood pressure (BP). Somatic afferent stimulation activates PVN neurons that project directly to the rostral ventrolateral medulla (rVLM), but little is known about the physiological actions and regulation of its neural activity. Since electroacupuncture (EA) stimulates somatic nerves to modulate sympathoexcitatory reflex responses, we hypothesized that the PVN and its projections to the rVLM participate in the sympathoexcitatory cardiovascular actions of EA. Cats were anesthetized, ventilated, and heart rate and BP monitored. Bradykinin (BK) applied every 10 min to the gallbladder induced consistent pressor responses. EA at acupoints P5–6 reduced the pressor responses for 60 min. Naloxone microinjection into the PVN restored the change in BP during BK‐induced pressor responses. Retrograde tracing from the rVLM showed EA‐related c‐Fos PVN neurons juxtaposed to endorphinergic PVN fibers. EA decreased splanchnic nerve‐evoked cardiovascular PVN neurons with direct projections to the rVLM for 60 min. Responses of cardiovascular barosensitive sympathoexcitatory rVLM neurons receiving median nerve input was reduced by EA and restored by PVN naloxone blockade. Thus, sympathoexcitatory PVN responses and a naloxone sensitive PVN‐rVLM pathway contribute to central neural processing during EA. Supported by HL‐72125.