Abstract
Brain-derived neurotrophic factor (BDNF) expression increases in the paraventricular nucleus of the hypothalamus (PVN) during stress, and our recent studies indicate that BDNF induces sympathoexcitatory and hypertensive responses when injected acutely or overexpressed chronically in the PVN. However, it remained to be investigated whether BDNF is involved in the mediation of stress-induced cardiovascular responses. Here we tested the hypothesis that inhibition of the high-affinity BDNF receptor TrkB in the PVN diminishes acute stress-induced cardiovascular responses. Male Sprague-Dawley rats were equipped with radiotelemetric transmitters for blood pressure measurement. BDNF-TrkB signaling was selectively inhibited by viral vector-mediated bilateral PVN overexpression of a dominant-negative truncated TrkB receptor (TrkB.T1, n = 7), while control animals ( n = 7) received green fluorescent protein (GFP)-expressing vector injections. Rats were subjected to acute water and restraint stress 3-4 wk after vector injections. We found that body weight, food intake, baseline mean arterial pressure (MAP), and heart rate were unaffected by TrkB.T1 overexpression. However, peak MAP increases were significantly reduced in the TrkB.T1 group compared with GFP both during water stress (GFP: 39 ± 2 mmHg, TrkB.T1: 27 ± 4 mmHg; P < 0.05) and restraint stress (GFP: 41 ± 3 mmHg, TrkB.T1: 34 ± 2 mmHg; P < 0.05). Average MAP elevations during the poststress period were also significantly reduced after both water and restraint stress in the TrkB.T1 group compared with GFP. In contrast, heart rate elevations to both stressors remained unaffected by TrkB.T1 overexpression. Our results demonstrate that activation of BDNF high-affinity TrkB receptors within the PVN is a major contributor to acute stress-induced blood pressure elevations. NEW & NOTEWORTHY We have shown that inhibition of the high-affinity brain-derived neurotrophic factor receptor TrkB in the paraventricular nucleus of the hypothalamus significantly reduces blood pressure elevations to acute stress without having a significant impact on resting blood pressure, body weight, and food intake.