The calibrated massage method was shown to be a reproducible method for applying massage pressures in rodents and lowering BP.

Research in our lab has demonstrated that perinatal exposure to the polybrominated‐dipheyl ether (PBDE) mixture, DE‐71, triggers pressor responses to hyperosmotic stress in adult rats. To evaluate the effect of ganglionic blockade (GB), dams were dosed with DE‐71 or corn‐oil daily from gestational day 4 through postnatal day (PND) 21. At PND 60 offspring received hyperosmotic (3.5 M NaCl) or normosmotic NaCl (0.9g%) i.p. with or without pentolinium (19.2mg/kg). After 3 hours, blood pressure was measured as % Δ baseline using sphygmomanometry under anesthesia. Hyperosmotic treatment produced a significant increase in systolic BP in PBDE‐rats compared to oil‐controls (22.99+ 2.55 vs 1.53+2.25%, n=22; p<0.001). GB partially occluded the pressor response in PBDE hyperosmotic rats, (12.85+1.30%, n=12; p<0.01), suggesting involvement of sympathetic nervous system (SNS). Adrenal catecholamine (CA) content, measured via fluorometric detection, was significantly reduced in PBDE hyperosmotic vs normosmotic rats (5.4+1.3 vs. 1.3+0.4 mM; n=21, p<0.05), suggesting exaggerated CA release. This was not compensated for by increased mRNA levels for TH, PNMT or PACAP mRNA. Plasma corticosterone was significantly elevated in PBDE hyperosmotic rats vs controls suggesting HPA overactivation. Adrenal HPA markers appeared to rise in the PBDE hyperosmotic rats, but this was not significant.In conclusion, adult hyperosmotic treatment in rats exposed to PBDEs perinatally show disrupted SNS and CA balance and hyperactive HPA axis. Our findings reveal that PBDEs may target endocrine and autonomic systems associated with stress responses.

Research suggests that chronic stress and subsequent activation of the sympathetic nervous system contribute to the development of hypertension. Recent work suggests that pituitary adenylate cyclase‐activating polypeptide (PACAP)‐dependent mechanisms sustain sympathoadrenal responses to prolonged but not acute stress. Group‐housed rats were placed in a sound chamber 25 cm from speakers randomly emitting four pure tones (5, 11, 15, and 19 kHz) for 30 min. After daily sound stress for 4 weeks rats were lightly anesthetized (isoflurane: 4% induction; 1.75% maintenance) and blood pressure was measured by tail‐cuff plethysmography. Stressed rats did not exhibit changes in diastolic blood pressure but showed a significant increase in systolic blood pressure compared to age‐matched controls: 118.3 ± 1.6 and 96.9 ± 1.7 mmHg, respectively (n=8; p<0.05) suggesting increased sympathetic drive originating in central autonomic and/or pre‐autonomic nuclei. Following blood pressure measurement, brains were removed and tissue from the hypothalamic paraventricular nucleus (PVN) was subjected to qPCR. In pilot experiments we observed elevated gene expression for PACAP (normalized to ribosomal protein L30) in stressed animals (9.10 ± 4.73) versus controls (1.12 ± 0.26; n=8; p=0.1). A similar elevation was observed for the PACAP receptor PAC1R: 5.27 ± 2.47 and 1.12 ± 0.21, respectively (n=8, p=0.1).

Magnocellular neuroendocrine cells (MNCs) in the supraoptic nucleus (SON) of the hypothalamus release the antidiuretic hormone, vasopressin (VP), in response to hyperosmotic and hypovolemic stimulation. Transient Receptor Potential Vanilloid 1 (TRPV1) receptor channels mediate osmosensitive electrical responses in MNCs and systemic VP release (Naeini et. al., 2006) but the specific mechanism linking TRPV1 channels and secretion of VP has yet to be determined. To examine the role of TRPV1 channels in somatodendritic VP release during hyperosmotic stimulation we treated acutely dissected SON punches in vitro with 350 mOsm/l Locke's solution in the presence and absence of the TRPV1 antagonist, 5‐iodoresiniferatoxin (SB366791). VP values were quantified using enzyme‐linked immunoassay. Hyperosmotic stimulation enhanced VP release and 1.5μM SB366791 attenuated this (p<0.05; n= 39). Mean (±s.e.m.) values for extracellular VP levels in isosmotic, hyperosmotic and hyperosmotic/SB366791 were 7.15±1.7, 11.1±2.8, 3.68±0.7 pg/ml μg protein, respectively. Doses of 0.15 and 10μM also reduced VP levels to 5.5±1.0 and 5.1±1.0, respectively. Immunohistochemistry showed TRPV1 immunoreactivity in SON MNCs. We conclude that TRPV1 channels in SON MNCs are activated during hyperosmotic stimulation and are required for somatodendritic VP secretion during osmotic challenge. (Supported by UC MEXUS)

Pituitary adenylate cyclase‐activating polypeptide (PACAP) is involved in hypothalamo‐pituitary‐adrenal (HPA) responses to stress but it's role at the adrenal level is unclear. Gene markers of HPA activation were measured by qPCR using adrenal glands of C57Bl6 and PACAP knockout (KO) mice. Restraint stress (1 hr) increased adrenal PACAP (p=0.01, n=13), steroidogenic acute regulatory protein (STAR) (p=0.02, n=7) and melanocortin receptor accessory protein (MRAP) mRNA (p=0.0003, n=8). Isolation stress for 8 weeks did not impact adrenal PACAP mRNA (p=0.27, n=22). However, isolation stress in PACAP KO mice increased adrenal adrenocorticotropic hormone receptor, melanocortin 2 (MC2R) mRNA (p=0.04, n=9) and MRAP (p=0.01, n=19) but not STAR and CYP11B1, which encodes for steroid 11β‐hydroxylase. Consistent with an association between elevated HPA activity and hyperactivity, PACAP KO mice showed a significant increase in distance traveled and velocity during 1 hr open field trial (p<0.0001; n=10). These results show that PACAP participates in adrenal HPA responses to acute and chronic stress via potentially different mechanisms. Support: UCMEXUS (KS, MC), Sigma Xi Research Society (KS), and APS (VJ, MV).