%0 Journal Article
%~ PubMed
%A Iigaya, Kamon
%A Müller-Ribeiro, Flávia Camargos de Figueirêdo
%A Horiuchi, Jouji
%A McDowall, Lachlan M
%A Nalivaiko, Eugene
%A Fontes, Marco A P
%A Dampney, Roger A L
%T Synchronized activation of sympathetic vasomotor, cardiac, and respiratory outputs by neurons in the midbrain colliculi.
%B American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
%D 2012
%C United States
%I American Physiological Society
%V 303
%N 6
%P R599-R610
%@ 1522-1490
%X 
%Z FOR Codes: 110901


%0 Journal Article
%~ PubMed
%A Horiuchi, Jouji
%A Atik, Alp
%A Iigaya, Kamon
%A McDowall, Lachlan M
%A Killinger, Suzanne
%A Dampney, Roger A L
%T Activation of 5-hydroxytryptamine 1a receptors suppresses cardiovascular responses evoked from the paraventricular nucleus.
%B American journal of physiology. Regulatory, integrative and comparative physiology
%D 2011
%C United States
%I American Physiological Society
%V 301
%N 4
%P R1088-97
%@ 1522-1490
%X Activation of central 5-hydroxytryptamine-1A (5-HT(1A)) receptors powerfully inhibits stress-evoked cardiovascular responses mediated by the dorsomedial hypothalamus (DMH), as well as responses evoked by direct activation of neurons within the DMH. The hypothalamic paraventricular nucleus (PVN) also has a crucial role in cardiovascular regulation and is believed to regulate heart rate and renal sympathetic activity via pathways that are independent of the DMH. In this study, we determined whether cardiovascular responses evoked from the PVN are also modulated by activation of central 5-HT(1A) receptors. In anesthetized rats, the increases in heart rate and renal sympathetic nerve activity evoked by bicuculline injection into the PVN were greatly reduced (by 54% and 61%, respectively) by intravenous administration of (??)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), an agonist of 5-HT(1A) receptors, but were then completely restored by subsequent administration of WAY-100635, a selective antagonist of 5-HT(1A) receptors. Microinjection of 8-OH-DPAT directly into the PVN did not significantly affect the responses to bicuculline injection into the PVN, nor did systemic administration of WAY-100635 alone. In control experiments, a large renal sympathoexcitatory response was evoked from both the PVN and DMH but not from the intermediate region in between; thus the evoked responses from the PVN were not due to activation of neurons in the DMH. The results indicate that activation of central 5-HT(1A) receptors located outside the PVN powerfully inhibits the tachycardia and renal sympathoexcitation evoked by stimulation of neurons in the PVN.
%Z FOR Codes: 110903 60603


%0 Journal Article
%~ PubMed
%A Dampney, R A L
%T Arcuate nucleus - a gateway for insulin's action on sympathetic activity.
%B Journal of Physiology
%D 2011
%C United Kingdom
%I Wiley-Blackwell Publishing Ltd.
%V 589
%N Pt 9
%P 2109-2110
%@ 1469-7793
%X 
%Z FOR Codes: 110901 60603


%0 Book Section
%A Dampney, Roger
%T The hypothalamus and autonomic regulation: An overview
%B Central Regulation of Autonomic Functions
%D 2011
%C United States
%I Oxford University Press
%V 
%N 
%P 47-61
%@ 9780195306637
%E Llewellyn-Smith, Ida J
%E Verberne, Anthony JM
%X 
%Z FOR Codes: 110306


%0 Journal Article
%~ PubMed
%A Brooks, Virginia L
%A Dampney, Roger A L
%A Heesch, Cheryl M
%T Pregnancy and the endocrine regulation of the baroreceptor reflex.
%B American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
%D 2010
%C United States
%I American Physiological Society
%V 299
%N 2
%P R439-R451
%@ 1522-1490
%X The purpose of this review is to delineate the general features of endocrine regulation of the baroreceptor reflex, as well as specific contributions during pregnancy. In contrast to the programmed changes in baroreflex function that occur in situations initiated by central command (e.g., exercise or stress), the complex endocrine milieu often associated with physiological and pathophysiological states can influence the central baroreflex neuronal circuitry via multiple sites and mechanisms, thereby producing varied changes in baroreflex function. During pregnancy, baroreflex gain is markedly attenuated, and at least two hormonal mechanisms contribute, each at different brain sites: increased levels of the neurosteroid 3alpha-hydroxy-dihydroprogesterone (3alpha-OH-DHP), acting in the rostral ventrolateral medulla (RVLM), and reduced actions of insulin in the forebrain. 3alpha-OH-DHP appears to potentiate baroreflex-independent GABAergic inhibition of premotor neurons in the RVLM, which decreases the range of sympathetic nerve activity that can be elicited by changes in arterial pressure. In contrast, reductions in the levels or actions of insulin in the brain blunt baroreflex efferent responses to increments or decrements in arterial pressure. Although plasma levels of angiotensin II are increased in pregnancy, this is not responsible for the reduction in baroreflex gain, although it may contribute to the increased level of sympathetic nerve activity in this condition. How these different hormonal effects are integrated within the brain, as well as possible interactions with additional potential neuromodulators that influence baroreflex function during pregnancy and other physiological and pathophysiological states, remains to be clearly delineated.
%Z FOR Codes: 111602


%0 Journal Article
%~ PubMed
%A Iigaya, Kamon
%A Horiuchi, Jouji
%A McDowall, Lachlan M
%A Dampney, Roger A L
%T Topographical specificity of regulation of respiratory and renal sympathetic activity by the midbrain dorsolateral periaqueductal gray.
%B American journal of physiology. Regulatory, integrative and comparative physiology
%D 2010
%C United States
%I American Physiological Society
%V 299
%N 3
%P R853-61
%@ 1522-1490
%X The midbrain periaqueductal gray (PAG) mediates the physiological responses to a wide range of stressors. It consists of four longitudinal columns that have different anatomical connections and functional properties. Previous anatomical and behavioral studies have led to the hypothesis that the dorsolateral PAG, but not the adjacent lateral and dorsomedial subregions, is a key center that integrates the behavioral response to acute psychological threatening stimuli. In this study, we tested whether, consistent with this hypothesis, activation of neurons in the dorsolateral PAG evokes a pattern of cardiovascular and respiratory responses that is distinct from that evoked from surrounding regions. Arterial pressure, heart rate, renal sympathetic nerve activity (RSNA), and phrenic nerve activity (PNA) were recorded simultaneously in urethane-anesthetized rats. Microinjections of very small amounts of d,l-homocysteic acid (750 pmol in 15 nl) were made in sites throughout the dorsomedial, dorsolateral, and lateral PAG subregions. Increases in RSNA of similar magnitude accompanied by small to moderate increases in arterial pressure and heart rate were evoked from all three PAG subregions. In contrast, large increases in both PNA burst rate (respiratory rate) and overall respiratory activity were evoked only from a highly circumscribed region that corresponded closely to the dorsolateral PAG subregion at an intermediate to caudal level. Within this region, the evoked increases in RSNA and respiratory activity were highly correlated (r = 0.914, P < 0.001), suggesting the possibility that a common population of "command neurons" within the dorsolateral PAG may generate both sympathetic and respiratory responses from this region.
%Z FOR Codes: 60603


%0 Journal Article
%~ PubMed
%A Dampney, Roger A L
%T Blood pressure regulation by C1 neurons in the rostral ventrolateral medulla: new light on the subject.
%B The Journal of Physiology
%D 2009
%C United Kingdom
%I Wiley-Blackwell Publishing Ltd.
%V 587
%N Pt 23
%P 5513
%@ 1469-7793
%X 
%Z FOR Codes: 110903


%0 Journal Article
%~ PubMed
%A Horiuchi, Jouji
%A McDowall, Lachlan M
%A Dampney, Roger A L
%T Vasomotor and respiratory responses evoked from the dorsolateral periaqueductal grey are mediated by the dorsomedial hypothalamus.
%B The Journal of Physiology
%D 2009
%C United Kingdom
%I Wiley-Blackwell Publishing Ltd.
%V 587
%N Pt 21
%P 5149-5162
%@ 1469-7793
%X Activation of neurons in the dorsomedial hypothalamus (DMH) evokes increases in mean arterial pressure (MAP), sympathetic activity, heart rate (HR) and respiratory activity. Results of previous studies suggest that the DMH-evoked increases in MAP and HR are mediated by neurons within the periaqueductal grey (PAG), but a recent study has proposed that the converse is also true, i.e. that increases in MAP and HR evoked from the PAG depend upon neuronal activity in the DMH. In this study in anaesthetized rats, we examined the functional relationship between the DMH and PAG in regulating renal sympathetic nerve activity (RSNA) and respiratory activity (determined by measuring phrenic nerve activity (PNA)). Bilateral microinjections of the neuronal inhibitor muscimol into the DMH virtually abolished the increases in MAP, RSNA and PNA burst rate and amplitude evoked from the dorsolateral (dl) PAG. In contrast, multiple bilateral injections of much larger (10 times) doses of muscimol or of the local anaesthetic lignocaine into sites in the dlPAG at three different rostrocaudal levels did not reduce the magnitude or duration of the sympathetic vasomotor and respiratory responses evoked by disinhibition of neurons in the DMH. Thus, sympathetic vasomotor and respiratory responses generated from the dlPAG are dependent upon neuronal activity in the DMH, but not the converse. The results of this study together with those of previous studies indicate that the PAG regulates cardiovascular and respiratory function via both ascending projections to the DMH and descending projections to the ventral medulla, that originate from different PAG subregions.
%Z FOR Codes: 110903 111603


%0 Journal Article
%~ PubMed
%A Dampney, Roger A L
%T Brain Angiotensin and Heart Failure. Further Evidence for a Critical Role of Mitogen-Activated Protein Kinases.
%B Hypertension
%D 2008
%C United States
%I Lippincott Williams and Wilkins
%V 52
%N 4
%P 621-2
%@ 1524-4563
%X 
%Z FOR Codes: 110903 111603


%0 Book Section
%A Dampney, Roger
%T Cardiovascular and Respiratory Reflexes: Physiology and Pharmacology
%B Clinical Autonomic Disorders
%D 2008
%C Baltimore
%I Lippincott Williams and Wilkins
%V 
%N 
%P 43-56
%@ 9780781773812
%E Low, Phillip A
%E Benarroch, Eduardo E
%X 
%Z FOR Codes: 110299 110901


%0 Journal Article
%~ PubMed
%A Dampney, R A L
%A Horiuchi, J
%A McDowall, L M
%T Hypothalamic mechanisms coordinating cardiorespiratory function during exercise and defensive behaviour.
%B Autonomic neuroscience : basic & clinical
%D 2008
%C Netherlands
%I Elsevier BV
%V 142
%N 1-2
%P 3-10
%@ 1566-0702
%X Defensive behaviour evoked by mild or moderate psychological stress as well as increased activity and arousal are part of everyday life in humans and other animals. Both defensive behaviour and exercise are associated with marked and often quite stereotyped changes in autonomic and respiratory function. These patterned responses are generated by feed-forward or "central command" mechanisms, and are also modulated by feedback from peripheral receptors. In this review we first describe the pattern of autonomic and respiratory changes associated with defensive behaviour and exercise, and then discuss the central mechanisms that generate these patterned responses in the light of recent studies, with a particular focus on the role of the dorsomedial hypothalamus (DMH). We consider the hypothesis that the cardiorespiratory changes associated with defensive behaviour and exercise may, at least in part, be driven by common central mechanisms. Finally, we discuss the possible role of the DMH in generating circadian rhythms in arterial blood pressure and heart rate, and also in generating longer-term increases in sympathetic activity in some types of hypertension.
%Z FOR Codes: 110901 111603


%0 Journal Article
%~ PubMed
%A Dampney, Roger A L
%T Is the RVLM a key site for sex-related differences in blood pressure regulation? Focus on "Sex differences in angiotensin signaling in bulbospinal neurons..."
%B American journal of physiology. Regulatory, integrative and comparative physiology
%D 2008
%C United States
%I American Physiological Society
%V 295
%N 4
%P R1147-8
%@ 1522-1490
%X 
%Z FOR Codes: 110903 1116


%0 Journal Article
%~ PubMed
%A Horiuchi, Jouji
%A McDowall, Lachlan M
%A Dampney, Roger A L
%T Role of 5-HT(1A) receptors in the lower brainstem on the cardiovascular response to dorsomedial hypothalamus activation.
%B Autonomic neuroscience : basic & clinical
%D 2008
%C Netherlands
%I Elsevier BV
%V 142
%N 1-2
%P 71-6
%@ 1566-0702
%X The dorsomedial hypothalamus (DMH) is an essential brain region for the integration of the physiological response to psychological stressors. The cardiovascular components of the response include increases in blood pressure, heart rate and the activity of sympathetic nerves to the kidney, skin, brown adipose tissue, and heart. Neurons in the rostral ventrolateral medulla (RVLM) and in the region of the medullary raphe are important components of the descending pathways that mediate the cardiovascular response to the DMH activation. Activation of 5-hydroxytryptamine 1A (5-HT(1A)) receptors in the brain leads to a suppression of the cardiac and sympathetic vasomotor components of the DMH-evoked response and of the response to acute psychological stress. In this study we showed that intracisternal injection of a low dose (1 microg/kg) of the 5-HT(1A) receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), significantly reduced the increases in heart rate and renal sympathetic nerve activity evoked by disinhibition of the DMH, but had no effect on these responses when injected intravenously. Subsequent intracisternal administration of the 5-HT(1A) receptor antagonist WAY-100635 restored the DMH-evoked cardiovascular responses to levels observed before 8-OH-DPAT administration. Bilateral microinjections of 8-OH-DPAT (200 pmol on each side) into the RVLM, however, did not significantly affect the cardiovascular response to disinhibition of the DMH. These observations demonstrate that activation of 5-HT(1A) receptors within the lower brainstem, but not in the RVLM, can powerfully suppress the cardiovascular response evoked from the DMH.
%Z FOR Codes: 110901 111603


%0 Journal Article
%~ PubMed
%A Tan, Peter S P
%A Killlinger, Suzanne
%A Horiuchi, Jouji
%A Dampney, Roger A L
%T Baroreceptor reflex modulation by circulating angiotensin II is mediated by AT1 receptors in the nucleus tractus solitarius.
%B American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
%D 2007
%C United States
%I American Physiological Society
%V 293
%N 6
%P R2267-R278
%@ 0363-6119
%X Circulating ANG II modulates the baroreceptor reflex control of heart rate (HR), at least partly via activation of ANG II type 1 (AT1) receptors on neurons in the area postrema. In this study, we tested the hypothesis that the effects of circulating ANG II on the baroreflex also depend on AT1 receptors within the nucleus tractus solitarius (NTS). In confirmation of previous studies in other species, increases in arterial pressure induced by intravenous infusion of ANG II had little effect on HR in urethane-anesthetized rats, in contrast to the marked bradycardia evoked by equipressor infusion of phenylephrine. In the presence of a continuous background infusion of ANG II, the baroreflex control of HR was shifted to higher levels of HR but had little effect on the baroreflex control of renal sympathetic activity. The modulatory effects of circulating ANG II on the cardiac baroreflex were significantly reduced by microinjection of candesartan, an AT1 receptor antagonist, into the area postrema and virtually abolished by microinjections of candesartan into the medial NTS. After acute ablation of the area postrema, a background infusion of ANG II still caused an upward shift of the cardiac baroreflex curve, which was reversed by subsequent microinjection of candesartan into the medial NTS. The results indicate that AT1 receptors in the medial NTS play a critical role in modulation of the cardiac baroreflex by circulating ANG II via mechanisms that are at least partly independent of AT1 receptors in the area postrema.
%Z FOR Codes: 110903 110502


%0 Journal Article
%~ PubMed
%A Dampney, R A L
%A Tan, P S P
%A Sheriff, M J
%A Fontes, M A P
%A Horiuchi, J
%T Cardiovascular effects of angiotensin II in the rostral ventrolateral medulla: the push-pull hypothesis.
%B Current hypertension reports
%D 2007
%C United States
%I Current Science Inc.
%V 9
%N 3
%P 222-227
%@ 1522-6417
%X Neurons within the rostral ventrolateral medulla (RVLM) play a pivotal role in the tonic and phasic control of blood pressure. This region also contains a high density of angiotensin II type 1 (AT1) receptors. There is evidence that tonic activation of AT1 receptors in the RVLM contributes to an increased sympathetic vasomotor activity in some models of hypertension. At the same time, under certain conditions, activation of AT1 receptors in the RVLM can cause sympathoinhibition. In this review we argue that the effect of endogenous angiotensin II in the RVLM on sympathetic vasomotor activity depends upon the balance between tonic excitatory and inhibitory effects on sympathetic premotor neurons mediated by AT1 receptors within this region, and that this balance may be altered in different physiological or pathophysiological conditions.
%Z FOR Codes: 110903


%0 Journal Article
%~ PubMed
%A Polson, J W
%A Dampney, R A L
%A Boscan, P
%A Pickering, A E
%A Paton, J F R
%T Differential baroreflex control of sympathetic drive by angiotensin II in the nucleus tractus solitarii.
%B American Journal of Physiology
%D 2007
%C United States
%I American Physiological Society
%V 293
%N 5
%P R1954-R1960
%@ 0363-6119
%X Microinjection of angiotensin II into the nucleus tractus solitarii attenuates the baroreceptor reflex-mediated bradycardia by inhibiting both vagal and cardiac sympathetic components. However, it is not known whether the baroreflex modulation of other sympathetic outputs (i.e., noncardiac) also are inhibited by exogenous angiotensin II (ANG II) in nucleus tractus solitarii (NTS). In this study, we determined whether there was a difference in the baroreflex sensitivity of sympathetic outflows at the thoracic and lumbar levels of the sympathetic chain following exogenous delivery of ANG II into the NTS. Experiments were performed in two types of in situ arterially perfused decerebrate rat preparations. Sympathetic nerve activity was recorded from the inferior cardiac nerve, the midthoracic sympathetic chain, or the lower thoracic-lumbar sympathetic chain. Increases in perfusion pressure produced a reflex bradycardia and sympathoinhibition. Microinjection of ANG II (500 fmol) into the NTS attenuated the reflex bradycardia (57% attenuation, P < 0.01) and sympathoinhibition of both the inferior cardiac nerve (26% attenuation, P < 0.05) and midthoracic sympathetic chain (37% attenuation, P < 0.05) but not the lower thoracic-lumbar chain (P = 0.56). We conclude that ANG II in the nucleus tractus solitarii selectively inhibits baroreflex responses in specific sympathetic outflows, possibly dependent on the target organ innervated.
%Z FOR Codes: 60603


%0 Journal Article
%~ PubMed
%A McDowall, Lachlan M
%A Horiuchi, Jouji
%A Dampney, Roger A L
%T Effects of disinhibition of neurons in the dorsomedial hypothalamus on central respiratory drive.
%B American Journal of Physiology: Regulatory, Integrative and Comparative Physiology
%D 2007
%C United States
%I American Physiological Society
%V 293
%N 4
%P R1728-R1735
%@ 0363-6119
%X Neurons within the dorsomedial hypothalamus (DMH) play a critical role in subserving the cardiovascular and neuroendocrine response to psychological stress. An increase in respiratory activity is also a characteristic feature of the physiological response to psychological stress, but there have been few studies of the role of DMH neurons in regulating respiratory activity. In this study we determined the effects of activation of DMH neurons on respiratory activity (assessed by measuring phrenic nerve activity, PNA) and the relationship between evoked changes in respiratory activity and changes in sympathetic vasomotor activity in spontaneously breathing urethane-anesthetized rats. Microinjections of bicuculline (4-40 pmol in 20 nl) into the DMH evoked dose-dependent increases in PNA burst frequency and amplitude. These were accompanied by dose-dependent decreases in mean tracheal CO(2) levels, indicative of hyperventilation. In control experiments, microinjections of bicuculline into sites adjacent to the DMH evoked much smaller or no changes in PNA. In experiments where renal sympathetic nerve activity (RSNA) was also measured, cycle-triggered averaging revealed that RSNA under resting conditions was partly correlated with the PNA, but in response to DMH disinhibition there was no consistent change in the amplitude of the respiratory-related variations in RSNA. The results indicate that DMH neurons can exert a powerful stimulatory effect on respiratory activity, causing hyperventilation. This is not associated with an increase in the degree of coupling between PNA and RSNA, indicating that the DMH-evoked increase in RSNA is not a consequence of increased central respiratory drive.
%Z FOR Codes: 110903


%0 Journal Article
%~ PubMed
%A Dampney, Roger A L
%T Angiotensin type 1A receptors on glial cells in rostral ventrolateral medulla and hypertension.
%B Hypertension
%D 2006
%C United States
%I Lippincott Williams & Wilkins
%V 47
%N 6
%P 1052-3
%@ 0194-911X
%X 
%Z FOR Codes: 110903


%0 Journal Article
%~ PubMed
%A Sheriff, Mohammed J
%A Fontes, Marco A P
%A Killinger, Suzanne
%A Horiuchi, Jouji
%A Dampney, Roger A L
%T Blockade of AT1 receptors in the rostral ventrolateral medulla increases sympathetic activity under hypoxic conditions.
%B American journal of physiology. Regulatory, integrative and comparative physiology
%D 2006
%C United States
%I American Physiological Society
%V 290
%N 3
%P R733-40
%@ 0363-6119
%X The role of ANG type 1 (AT1) receptors in the rostral ventrolateral medulla (RVLM) in the maintenance of sympathetic vasomotor tone in normotensive animals is unclear. In this study, we tested the hypothesis that AT1 receptors make a significant contribution to the tonic activity of presympathetic neurons in the RVLM of normotensive rats under conditions where the excitatory input to these neurons is enhanced, such as during systemic hypoxia. In urethane-anesthetized rats, microinjections of the AT1 receptor antagonist candesartan in the RVLM during moderate hypoxia unexpectedly resulted in substantial increases in arterial pressure and renal sympathetic nerve activity (RSNA), whereas under normoxic conditions the same dose resulted in no significant change in arterial pressure and RSNA. Under hypoxic conditions, and after microinjection of the GABA(A) receptor antagonist bicuculline in the RVLM, subsequent microinjection of candesartan in the RVLM resulted in a significant decrease in RSNA. In control experiments, bilateral microinjections in the RVLM of the compound [Sar1,Thr8]ANG II (sarthran), which decreases sympathetic vasomotor activity via a mechanism that is independent of AT1 receptors, significantly reduced arterial pressure and RSNA under both normoxic and hypoxic conditions. The results indicate that, at least under some conditions, endogenous ANG II has a tonic sympathoinhibitory effect in the RVLM, which is dependent on GABA receptors. We suggest that the net effect of endogenous ANG II in this region depends on the balance of both tonic excitatory and inhibitory actions on presympathetic neurons and that this balance is altered in different physiological or pathophysiological conditions.
%Z FOR Codes: 110903 111603


%0 Journal Article
%~ PubMed
%A McDowall, Lachlan M
%A Dampney, Roger A L
%T Calculation of the Threshold and Saturation Points of Sigmoidal Baroreflex Function Curves.
%B American journal of physiology. Heart and circulatory physiology
%D 2006
%C United States
%I American Physiological Society
%V 291
%N 
%P H2003-7
%@ 0363-6135
%X The logistic sigmoid function curve provides an accurate description of the baroreflex input-output relationship and is the most commonly used equation for this purpose. The threshold (Thr) and saturation (Sat) values for the baroreflex are commonly defined as the values of mean arterial pressure (MAP) at which the reflexly controlled variable (e.g., heart rate or sympathetic nerve activity) is within 5% of the upper or lower plateau, respectively, of the sigmoid function. These values are referred to here as Thr(5%) and Sat(5%). In many studies, Thr and Sat are calculated with the equations Thr = A(3) - 2.0/A(2) and Sat = A(3) + 2.0/A(2), where A(3) is the value of MAP at the point where the reflexly controlled variable is at the midpoint of its range and A(2) is the gain coefficient. Although it is commonly stated that the values of Thr and Sat calculated with these equations represent Thr(5%) and Sat(5%), we show here that instead they are significantly greater and less than Thr(5%) and Sat(5%), respectively. Furthermore, the operating range (difference between Thr and Sat) calculated with these equations is 32% less than the difference between Thr(5%) and Sat(5%). We further show that the equations that provide correct values of Thr(5%) and Sat(5%) are Thr(5%) = A(3) - 2.944/A(2) and Sat(5%) = A(3) + 2.944/A(2). We propose that these be used as the standard equations for calculating threshold and saturation values when a logistic sigmoid function is used to model the open-loop baroreflex function curve.
%Z FOR Codes: 110903


%0 Journal Article
%~ PubMed
%A Horiuchi, J
%A McDowall, L M
%A Dampney, R A L
%T Differential control of cardiac and sympathetic vasomotor activity from the dorsomedial hypothalamus.
%B Clinical and experimental pharmacology & physiology
%D 2006
%C Australia
%I Blackwell Publishing Asia
%V 33
%N 12
%P 1265-8
%@ 0305-1870
%X 1. The dorsomedial hypothalamus (DMH) plays a crucial role in mediating the cardiovascular responses to different stressors, including acute psychological stress and cold stress. Activation of neurons in the DMH evokes increases in arterial pressure and in the activity of sympathetic nerves innervating the heart, blood vessels and brown adipose tissue. The descending pathways from the DMH to the spinal sympathetic outflow include synapses with neurons in medullary nuclei and possibly other brain stem regions. 2. Recent studies from our and other laboratories have indicated that neurons in the rostral ventrolateral medulla (RVLM) and in the region of the raphe pallidus (RP) in the medulla are important components of the descending pathways that mediate the cardiovascular response to activation of the DMH. Neurons in the RP primarily mediate the sympathetic cardiac components of the DMH-evoked response, whereas the RVLM neurons primarily mediate the sympathetic vasomotor component. 3. Activation of DMH neurons not only increases heart rate and sympathetic vasomotor activity, but also resets the baroreceptor reflex such that it remains effective, without any decrease in sensitivity, over a higher operating range of arterial pressure. 4. Activation of 5-hydroxytryptamine 5-HT(1A) receptors in the medulla oblongata leads to a selective suppression of cardiac and sympathetic vasomotor components of the DMH-evoked response, but does not affect sympathetic reflex responses evoked from baroreceptors or chemoreceptors. Thus, central 5-HT(1A) receptors modulate cardiovascular responses evoked from the DMH in a highly potent but selective fashion.
%Z FOR Codes: 110903


%0 Journal Article
%~ Isi
%A Horiuchi, J.
%A Dampney, R. A. L.
%T Sympathetic descending pathway and neuro-transmitters of the cardiovascular response during acute stress.
%B Neuroscience Research
%D 2006
%C Ireland, Japan
%I Elsevier Ireland Ltd
%V 55
%N 
%P S21-S21
%@ 0168-0102
%X 
%Z FOR Codes: 110901