Leptin and splanchnic sympathetic nerve activity and heart rate

Baoxin Li, Zhigang Shi, Priscila A. Cassaglia, Virginia L. Brooks Hypertension is available at http://hyper.ahajournals.org DOI: 10.1161/HYPERTENSIONAHA.111.00518 In this article they tested whether leptin was acting in the Forebrain or in the brainstem in order to cause increases in sympathetic nerve activity. They also wanted to know what effects leptin had on the baroreceptor reflex. So they recorded splanchnic sympathetic activity (SSNA), Lumbar sympathetic activity (LSNA), renal sympathetic activity (RSNA) along with mean arterial pressure (MAP) and heart rate (HR). First they gave SNP and PE in order to generate a baroreflex curve. Then they infused leptin 3ug and 1.5 ug into the lateral cerebral ventricle (LV) and also the fourth ventricle (4V). They want to know if leptin was also affecting parasympathetic to the heart, so they gave methscopolamine an anticholinergic agent through iv. Their results showed that after one hour and two hours there was a significant increase in LSNA and RSNA compared to control levels for 3ug infusion into the LV. With the 1.5 ug infusion into the LV they saw an significant increase only after two hours for LSNA compared to the control. Also there was significant increase in SSNA in response to the 3ug LV infusion compared to the control. When they generated the baroreflex curves for animal before and after leptin infusion they found that lumbar both doses infused into the LV increase the baroreflex gain and increase the baroreflex maximum. As for the RSNA, LV 3ug infusion leads to increases in the baroreceptor reflex gain and maximum. SSNA the LV 3ug infusion lead only to an increase in baroreflex maximum. When leptin is given under control conditions it causes an increase in HR. When they at leptin effects on parasympathetic and sympathetic innervation to the heart they found that methscopolamine prevented leptin from altering HR. They also tested leptin in the brainstem and found no significant results to report. The conclusion was that leptin mediates its effects on different sympathetic beds and blood pressure by acting in the forebrain. Leptin actions in the forebrain also restrain parasympathetic activity to the heart. -MD