Cardiovascular sympathoinhibitory neurons form an extended longitudinal column in cat lateral medulla

Dempesy, Colby W.; Richardson, Donald E.; Fontana, Charles J.

doi:10.1016/0006-8993(93)91257-s

Cited by 10 publications

(3 citation statements)

References 22 publications

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“…In this respect, Wu and coworkers (37) demonstrated, in cats, involvement of NO in glutamaterelated excitation in the rVLM, whereas Zanzinger's group (38) observed inhibitory effect of NO on rVLM following application of NO donors and inhibitors in larger volumes (500 nl) than usual (50 -100 nl). Such large volumes may result in diffusion of drugs to regions outside the rVLM, such as lateral tegmental field and medial depressor area, that contain different concentrations and hence ratios of sympathoinhibitory and sympathoexcitatory neurons (8,11). In addition, some studies are internally inconsistent, showing no response of baseline BP and inhibition of glutamate-induced BP responses following both antagonism of NO production and administration of NO donors in the cat rVLM (7).…”

Section: Discussionmentioning

confidence: 98%

Nitric oxide in rostral ventrolateral medulla regulates cardiac-sympathetic reflexes: role of synthase isoforms

Guo

Tjen‐A‐Looi

et al. 2009

American Journal of Physiology-Heart and Circulatory Physiology

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Our previous studies have shown that nitric oxide (NO) synthase (NOS)-containing neurons in the rostral ventrolateral medulla (rVLM) are activated during cardiac sympathoexcitatory reflexes (Refs. 12 and 13). However, the precise function of NO in the rVLM in regulation of these reflexes has not been defined. Three isoforms of NOS, including neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS), are located in the rVLM. We explored the role of NO, derived from different NOS isoforms in the rVLM, in processing cardiac-sympathetic reflexes using whole animal reflex and electrophysiological approaches. We found that, in anesthetized cats, increased mean arterial blood pressure and renal sympathetic nerve activity elicited by epicardial application of bradykinin (BK; 1-10 microg/ml, 50 microl) were significantly attenuated following unilateral rVLM microinjection of the nonselective NOS inhibitor, N(omega)-nitro-L-arginine methyl ester (50 nmol/50 nl), or a specific nNOS inhibitor, 7-nitroindazole (7-NI; 5-10 pmol/50 nl; both P < 0.05). In contrast, the responses of mean arterial blood pressure and renal sympathetic nerve activity to cardiac BK stimulation were unchanged by unilateral rVLM microinjection of N(omega)-nitro-D-arginine methyl ester (inactive isomer of N(omega)-nitro-L-arginine methyl ester, 50 nmol/50 nl), 3-6% methanol (7-NI vehicle), N(6)-(1-iminoethyl)-L-lysine (250 pmol/50 nl; iNOS inhibitor), or N(5)-(1-iminoethyl)-L-ornithine (250 nmol/50 nl; eNOS inhibitor). Furthermore, in separate cats, we noted that iontophoresis of 7-NI (0.1 mM) reduced the increased discharge of cardiovascular sympathoexcitatory rVLM neurons in response to cardiac stimulation with BK (P < 0.05). These neurons were characterized by their responses to inputs from baroreceptors, and their cardiac rhythmicity was determined through frequency and time domain analyses, correlating their discharge to arterial blood pressure and cardiac sympathetic efferent nerve activity. These data suggest that NO, specifically nNOS, mediates sympathetic cardiac-cardiovascular responses through its action in the rVLM.

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Section: Discussionmentioning

confidence: 98%

Nitric oxide in rostral ventrolateral medulla regulates cardiac-sympathetic reflexes: role of synthase isoforms

Guo

Tjen‐A‐Looi

et al. 2009

American Journal of Physiology-Heart and Circulatory Physiology

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“…This area also has been implicated in cardiovascular function and has been called a sympathoinhibitory area (Dempesy et al, 1991(Dempesy et al, , 1993 or the medullary cerebrovascular area (Golanov et al, 2000a,b). The role played by the CPA in modulating the neurons in the lateral medulla is unknown.…”

Section: Functional Implications Of the Cpamentioning

confidence: 98%

Defining projections from the caudal pressor area of the caudal ventrolateral medulla

Sun

Panneton

2004

J. Comp. Neurol.

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We previously defined a functional area in the caudal medulla oblongata that elicits an increase in arterial pressure when stimulated (Sun and Panneton [2002] Am. J. Physiol. 283:R768-R778). In the present study, anterograde and retrograde tracing techniques were used to investigate the projections of this caudal pressor area (CPA) to the medulla and pons. Injections of biotinylated dextran amine into the CPA resulted in numerous labeled fibers with varicosities in the ipsilateral subnucleus reticularis dorsalis, commissural subnucleus of the nucleus tractus solitarii, lateral medulla, medial facial nucleus, A5 area, lateral vestibular nucleus, and internal lateral subnucleus of the parabrachial complex. Sparser projections were found ipsilaterally in the pressor and depressor areas of the medulla and the spinal trigeminal nucleus and contralaterally in the CPA. Injections of the retrograde tracer Fluoro-Gold into these areas labeled neurons in the CPA as well as the nearby medullary dorsal horn and reticular formation. However, we conclude that the CPA projects preferentially to the subnucleus reticularis dorsalis, commissural nucleus tractus solitarii, lateral medulla, A5 area, and internal lateral parabrachial nucleus. Weaker projections were seen to the CVLM and RVLM and to the contralateral CPA. The projection to the facial nucleus arises from nearby reticular neurons, whereas projections to the vestibular nucleus arise from the lateral reticular nucleus. Labeled neurons in the CPA consisted mostly of small bipolar and some triangular neurons. The projection to the CVLM, or to A5 area, may provide for the increase in arterial pressure with CPA stimulation. However, most of the projections described herein are to nuclei implicated in the processing of noxious information. This implies a unique role for the CPA in somatoautonomic regulation.

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“…Bauer, Iwamoto & Waldrop (1989) (Dempsey et al 1991;Dempsey, Richardson & Fontana, 1993). Additionally, it was recently-reported that a pressor area (4-5 mm rostral to the obex) exists in the dorsomedial medulla, ventral to the vestibular nuclei in rabbits (Hirooka, Polson, Dampney, 1994 (Hancock, 1988 (Wahlestedt & Reis, 1993 In conclusion, these data are of interest in understanding the possible role of NPY in the central neural control of arterial pressure during muscular contraction.…”

Section: Resultsmentioning

confidence: 90%

Neuropeptide Y‐like substances are released from the rostral brainstem of cats during the muscle pressor response.

Williams¹

1996

The Journal of Physiology

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1. In this study, the release of immunoreactive neuropeptide Y (NPY)-like substances (irNPYs) was measured from the rostral brainstem in response to fatiguing isometric contractions of the hindlimb muscle of cats anaesthetized with a-chloralose. 2. The irNPYs were measured using a solid phase autoradiographic immunoassay. NPY antibody-coated glass microelectrodes were inserted stereotaxically into the rostral brainstem during rest and contractions. Control procedures such as passive leg flexing, stimulation of the central end of the cut tibial nerve, brief repeated carotid occlusions and carotid sinus nerve stimulations were performed to determine whether patterns of release of irNPYs were specific to the pathways activated during the muscle pressor response. 3. During isometric contractions, the mean arterial blood pressure (MABP) and heart rate (HR) increased by 60-70 mmHg and 15-20 beats min', respectively. Only the brief carotid occlusions caused a similar increase in MABP and HR. 4. During isometric contractions, less irNPYs were released from sites in the lateral reticular nucleus, lateral tegmental field and vestibular nuclei at a level in the brainstem 4 0-4 4 mm rostral to the obex. In contrast, irNPYs were released from sites near the lateral tegmental field and nucleus ambiguus at a more caudal level tested (1-3 mm anterior to the obex) in response to contractions. Brief carotid occlusions caused a release of irNPYs from the lateral reticular nucleus on the contralateral side of the brainstem (at 3-5 mm anterior to the obex). None of the other procedures resulted in a release of irNPYs from these sites in the brainstem. 5. These data indicate there are differences in the patterns of release of irNPYs in response to activation of reflex pathways which increase arterial pressure. Given the sites in the rostral brainstem where irNPYs were released, irNPYs may be involved with the central regulation of arterial pressure during the muscle pressor response.

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Cardiovascular sympathoinhibitory neurons form an extended longitudinal column in cat lateral medulla

Cited by 10 publications

References 22 publications

Nitric oxide in rostral ventrolateral medulla regulates cardiac-sympathetic reflexes: role of synthase isoforms

Nitric oxide in rostral ventrolateral medulla regulates cardiac-sympathetic reflexes: role of synthase isoforms

Defining projections from the caudal pressor area of the caudal ventrolateral medulla

Neuropeptide Y‐like substances are released from the rostral brainstem of cats during the muscle pressor response.

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