. Attenuated defense response and low basal blood pressure in orexin knockout mice. Am J Physiol Regul Integr Comp Physiol 285: R581-R593, 2003. First published May 15, 2003 10.1152/ ajpregu.00671.2002The perifornical area of the hypothalamus has been known as the center for the defense response, or "fight or flight" response, which is characterized by a concomitant rise in arterial blood pressure (AP), heart rate (HR), and respiratory frequency (Rf). We examined whether orexin, a recently identified hypothalamic neuropeptide, contributes to the defense response and basal cardiovascular regulation using orexin knockout mice. Microinjection of a GABA-A receptor antagonist, bicuculline methiodide (0.1-1 mM in 20 nl), to the perifornical area in urethane-anesthetized wild-type mice elicited dose-dependent increases in AP, HR, and Rf. Although similar changes were observed in orexin knockout mice, intensities were smaller and duration was shorter than those in wild-type mice. Moreover, in an awake and freely moving condition, telemeter-indwelling orexin knockout mice showed diminished cardiovascular and behavioral responses to emotional stress in the residentintruder test. We also found that basal AP in orexin knockout mice was significantly lower in both anesthetized (117 Ϯ 8 mmHg in wild type and 92 Ϯ 3 in knockout) and conscious (125 Ϯ 6 mmHg in wild type and 109 Ϯ 2 in knockout) conditions. ␣-Adrenergic blockade with prazosin or ganglion blockade with hexamethonium canceled the difference in basal AP. HR and cardiac contractile parameters by echocardiography did not differ between the two strains of mice. These results indicate lower sympathetic vasoconstrictor tone in knockout mice. The present study suggests that orexin-containing neurons in the perifornical area play a role as one of the efferent pathways of defense response and also operate as a regulator of AP at basal condition by activating sympathetic outflow.hypothalamus; stress; respiration; sympathetic nervous system; circadian rhythm OREXIN A and B, also known as hypocretin 1 and 2, are recently identified neuropeptides that consist of 33 and 28 amino acids, respectively (10, 46). They are proteolytically derived from the same precursor peptide (prepro-orexin) and exert a variety of functions by acting on orexin receptor type 1 and/or type 2. Orexin-containing neuron cell bodies are located exclusively in the lateral and dorsal hypothalamic areas and their axons diffusely innervate almost the entire central nervous system (6,9,10,38,39,44,46). This anatomic feature establishes the bases that orexin contributes to multiple physiological functions, including feeding behavior (46), energy homeostasis (46, 54), sleep-wake cycle (5), and regulation of the autonomic and neuroendocrine systems (9,22,44,54).Several laboratories have proposed a possible contribution of orexin in cardiovascular regulation by observing the effects of exogenously administered orexins. Orexins on intracerebroventricular injection increased arterial blood pressure (AP), heart ra...

Abstract-␣-Calcitonin gene-related peptide (␣CGRP) is a pleiotropic neuropeptide implicated in a variety of physiological processes. To better understand the biological functions of ␣CGRP, we developed an ␣CGRP-null mouse model using a gene targeting approach. Recordings of mean arterial pressure (MAP) and heart rate (HR) showed that basal MAP and HR were significantly higher in both anesthetized and conscious, unrestrained ␣CGRP-null mice than in corresponding wild-type mice. The elevated MAP in ␣CGRP-null mice was shown to be the result of elevated peripheral vascular resistance by ␣-adrenergic blockade with prazosin and by transthoracic echocardiogram, which revealed no significant differences between ␣CGRP-null and wild-type mice in the stroke volume, fractional shortening, and ejection fraction. Moreover, evaluation of autonomic nervous activity by measuring HR after pretreatment of atropine and/or atenolol and by analyzing arterial baroreceptor reflexes showed sympathetic nervous activity to be significantly elevated in ␣CGRP-null mice; elevated levels of urinary catecholamine metabolites and decreased HR variability in mutant mice were also consistent with that finding. These findings suggest that ␣CGRP contributes to the regulation of cardiovascular function through inhibitory modulation of sympathetic nervous activity. Key Words: calcitonin gene-related peptide Ⅲ gene targeting Ⅲ blood pressure Ⅲ autonomic nervous system Ⅲ hypertension C alcitonin gene-related peptide (CGRP) is a 37-amino acid vasoactive neuropeptide produced by tissue-specific alternative splicing of the primary transcript of the calcitonin/ ␣CGRP gene. 1 While calcitonin (CT), which controls calcium homeostasis, is expressed almost exclusively in the C cells of the thyroid gland, ␣CGRP is widely distributed in the central and peripheral nervous systems in mammals. In addition, a second CGRP isoform, ␤CGRP, is encoded by a different gene locus and is expressed almost exclusively in specific neuronal sites. 2 These two CGRP isoforms-␣ and ␤ in rat and I and II in humans-exhibit overlapping biological activities in most vascular beds. 3 Within the nervous system, CGRP immunoreactivity has been detected in spinal cord motor neurons, dorsal root ganglia, and motor nerve endings. 4 Other neuropeptides, the tachykinins, which include substance P (SP) and neurokinin A (NKA), exhibit similar expression patterns to ␣CGRP in several regions of the nervous system. ␣CGRP and tachykinins coexist in primary afferent neurons, forming the part of the so-called nonadrenergic, noncholinergic (NANC) nervous system, 5 and their release from sensory pain fibers has been implicated in the perception of pain.NANC neurons containing ␣CGRP are also widely distributed among autonomic fibers innervating the vasculature; for example, they are found in blood vessels at the junction of the adventitia and the media passing into the muscle layer. 5 Moreover, ␣CGRP is a potent vasodilator, 6 and several investigators have claimed that ␣CGRP may play a key role in regu...

We demonstrated previously that membrane depolarization and excitatory receptor agonists such as noradrenaline induce Ca2+-dependent Rho activation in VSM (vascular smooth muscle), resulting in MP (myosin phosphatase) inhibition through the mechanisms involving Rho kinase-mediated phosphorylation of its regulatory subunit MYPT1. In the present study, we show in de-endothelialized VSM strips that the PI3K (phosphoinositide 3-kinase) inhibitors LY294002 and wortmannin inhibited KCl membrane depolarization- and noradrenaline-induced Rho activation and MYPT1 phosphorylation, with concomitant inhibition of MLC (20-kDa myosin light chain) phosphorylation and contraction. LY294002 also augmented de-phosphorylation of MLC and resultantly relaxation in KCl-contracted VSM, whereas LY294002 was much less effective or ineffective under the conditions in which MP was inhibited by either a phosphatase inhibitor or a phorbol ester in Rho-independent manners. VSM express at least four PI3K isoforms, including the class I enzymes p110alpha and p110beta and the class II enzymes PI3K-C2alpha and -C2beta. The dose-response relationships of PI3K-inhibitor-induced inhibition of Rho, MLC phosphorylation and contraction were similar to that of PI3K-C2alpha inhibition, but not to that of the class I PI3K inhibition. Moreover, KCl and noradrenaline induced stimulation of PI3K-C2alpha in a Ca2+-dependent manner, but not of p110alpha or p110beta. Down-regulation of PI3K-C2alpha expression by siRNA (small interfering RNA) inhibited contraction and phosphorylation of MYPT1 and MLC in VSM cells. Finally, intravenous wortmannin infusion induced sustained hypotension in rats, with inhibition of PI3K-C2alpha activity, GTP-loading of Rho and MYPT1 phosphorylation in the artery. These results indicate the novel role of PI3K-C2alpha in Ca2+-dependent Rho-mediated negative control of MP and thus VSM contraction.

A 62-year-old man was admitted with increasing palpitations. Radiography of the chest demonstrated a calcified mass. Magnetic resonance imaging revealed compression of the right ventricle by a tumor. At the time of cardiac catheterization, the coronary arteries were found not to supply blood flow of the mass, and no dip-and-plateau pattern was seen in the right ventricular pressure measurements. At the time of surgery, the mass was found to be a focal calcified thickening of the pericardium containing only pus. The thickening resembled an oval pericardial tumor.Microbiologic examination of the pus revealed Propionibacterium acnes. (Internal Medicine 38: 355-358, 1999)