Intracellular recording from sympathetic preganglionic neurons in cat lumbar spinal cord

Pilowsky, Paul M.; Llewellyn‐Smith, Ida J.; Arnolda, Leonard F; Minson, Jane B; Chalmers, John

doi:10.1016/0006-8993(94)91476-1

Cited by 30 publications

(20 citation statements)

References 61 publications

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“…Questions could also be raised about the accessibility of PACAP to the SPN. First, there is evidence that some dendrites of SPN reach the surface of the spinal cord (44). Second, although the SPN may indeed be less accessible to intrathecal infusion of PACAP, the time course of the responses following PACAP administration is consistent with this fact.…”

Section: Discussionmentioning

confidence: 84%

Intrathecal PACAP-38 causes increases in sympathetic nerve activity and heart rate but not blood pressure in the spontaneously hypertensive rat

Farnham

Inglott

Pilowsky

2011

American Journal of Physiology-Heart and Circulatory Physiology

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Farnham MM, Inglott MA, Pilowsky PM. Intrathecal PACAP-38 causes increases in sympathetic nerve activity and heart rate but not blood pressure in the spontaneously hypertensive rat. Am J Physiol Heart Circ Physiol 300: H214 -H222, 2011. First published October 15, 2010 doi:10.1152/ajpheart.00662.2010.-The rostral ventrolateral medulla contains presympathetic neurons that project monosynaptically to sympathetic preganglionic neurons (SPN) in the spinal cord and are essential for the tonic and reflex control of the cardiovascular system. SPN directly innervate the adrenal medulla and, via postganglionic axons, affect the heart, kidneys, and blood vessels to alter sympathetic outflow and hence blood pressure. Over 80% of bulbospinal, catecholaminergic (C1) neurons contain pituitary adenylate cyclaseactivating polypeptide (PACAP) mRNA. Activation of PACAP receptors with intrathecal infusion of PACAP-38 causes a robust, prolonged elevation in sympathetic tone. Given that a common feature of most forms of hypertension is elevated sympathetic tone, this study aimed to determine in the spontaneously hypertensive rat (SHR) and the Wistar Kyoto rat (normotensive control) 1) the proportion of C1 neurons containing PACAP mRNA and 2) responsiveness to intrathecal PACAP-38. We further investigated whether intrathecal infusion of the PACAP antagonist, PACAP(6 -38), reduces the hypertension in the SHR. The principal findings are that 1) the proportion of PACAP mRNA-containing C1 neurons is not different between normotensive and hypertensive rats, 2) intrathecal PACAP-38 causes a strain-dependent, sustained sympathoexcitation and tachycardia with variable effects on mean arterial pressure in normotensive and hypertensive rats, and 3) PACAP(6 -38) effectively attenuated the effects of intrathecal PACAP-38, but had no effect alone, on any baseline variables. This finding indicates that PACAP-38 is not tonically released in the spinal cord of rats. A role for PACAP in hypertension in conscious rats remains to be determined. sympathetic activity; spinal cord; pituitary adenylate cyclase-activating polypeptide THE ROSTRAL VENTROLATERAL MEDULLA (RVLM) is crucial for the tonic and reflex control of the cardiovascular system (see Refs. 15 and 43 for reviews). RVLM presympathetic neurons are commonly defined as being inhibited following baroreceptor activation and having a spinal axon (2, 28, 29). Neurochemically, 60 -80% of presympathetic neurons are C1 neurons (29,42,48,49), having all of the enzymes required for adrenaline synthesis. Presympathetic RVLM neurons project monosynaptically to sympathetic preganglionic neurons (SPN) in the intermediolateral (IML) cell column of the spinal cord (34,38). SPN, in turn, regulate the activity of the heart, kidneys, blood vessels, and adrenal chromaffin cells, thereby determining sympathetic outflow and ultimately blood pressure.Pituitary adenylate cyclase-activating polypeptide (PACAP) is an excitatory 38-amino-acid peptide originally identified in ovine hypothalamus (32) that also exists as a...

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Section: Discussionmentioning

confidence: 84%

Intrathecal PACAP-38 causes increases in sympathetic nerve activity and heart rate but not blood pressure in the spontaneously hypertensive rat

Farnham

Inglott

Pilowsky

2011

American Journal of Physiology-Heart and Circulatory Physiology

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“…7%). These cardiovascular sympathetic preganglionic neurons generally have small somata, but extremely extensive dendritic trees (Pilowsky et al 1994a). The large amount of axonal arborizations from PNMT immunoreactive terminals in the intermediolateral cell column combined with the extensive dendritic arborizations of sympathetic preganglionic neurons suggests the possibility of considerable divergence in the bulbospinal input pathways.…”

Section: (D) Motor Pathwaysmentioning

confidence: 99%

Differential regulation of the central neural cardiorespiratory system by metabotropic neurotransmitters

Pilowsky

Lung

Spirovski

et al. 2009

Phil. Trans. R. Soc. B

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Central neurons in the brainstem and spinal cord are essential for the maintenance of sympathetic tone, the integration of responses to the activation of reflexes and central commands, and the generation of an appropriate respiratory motor output. Here, we will discuss work that aims to understand the role that metabotropic neurotransmitter systems play in central cardiorespiratory mechanisms. It is well known that blockade of glutamatergic, gamma-aminobutyric acidergic and glycinergic pathways causes major or even complete disruption of cardiorespiratory systems, whereas antagonism of other neurotransmitter systems barely affects circulation or ventilation. Despite the lack of an 'all-or-none' role for metabotropic neurotransmitters, they are nevertheless significant in modulating the effects of central command and peripheral adaptive reflexes. Finally, we propose that a likely explanation for the plethora of neurotransmitters and their receptors on cardiorespiratory neurons is to enable differential regulation of outputs in response to reflex inputs, while at the same time maintaining a tonic level of sympathetic activity that supports those organs that significantly autoregulate their blood supply, such as the heart, brain, retina and kidney. Such an explanation of the data now available enables the generation of many new testable hypotheses.

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“…Respiratory rhythms in sympathetic nerve activity have been observed for many years (Adrian et al, 1932;Bainton et al, 1985;Bachoo and Polosa, 1987;Numao et al, 1987;Czyzyk-Krzeska and Trzebski, 1990;Pilowsky et al, 1994a), but the central sites at which this respiratory modulation is imposed are not well established. One possibility is that neurons in the medulla oblongata that are involved in respiratory rhythm generation also provide a synaptic input to presympathetic neurons in the rostral ventrolateral medulla (RVLM), which in turn synapse with sympathetic preganglionic neurons in the spinal cord (Bachoo and Polosa, 1985;Gilbey et al, 1986;Terui et al, 1986;Guyenet et al, 1990;Pilowsky et al, 1996).…”

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confidence: 96%

B�tzinger neurons project towards bulbospinal neurons in the rostral ventrolateral medulla of the rat

et al. 1997

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Sympathetic nerve activity often fluctuates with the respiratory cycle, but the central neurons that impose this respiratory modulation have not been conclusively identified. In the present study, we used intracellular recording and dye-filling to identify expiratory neurons in the Bötzinger complex. Our aim was to see if Bötzinger neurons project towards putative cardiovascular neurons in the rostral ventrolateral medulla. In the first series of experiments, histochemistry and immunohistochemistry were used to reveal the labelled Bötzinger neurons and neurons immunoreactive for tyrosine hydroxylase. Two out of four Bötzinger neurons had axon varicosities that were closely apposed to tyrosine hydroxylase-immunoreactive neurons with cell bodies located within 0.6 mm caudal to the facial nucleus (three and five close appositions, respectively). In a second series of studies, rats were injected with cholera toxin B into the intermediolateral cell column of the spinal cord 4-7 days before the electrophysiological recording. Eight of the fourteen labelled Bötzinger neurons had a direct projection towards cholera toxin B-labelled neurons in the rostral ventrolateral medulla. Close appositions were found on both somata and proximal dendrites (5 +/- 2 close appositions/neuron, n = 8). The present study supports the idea that a direct projection from Bötzinger neurons to presympathetic neurons in the rostral medulla plays a role in the respiratory modulation of sympathetic nerve activity.

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Intracellular recording from sympathetic preganglionic neurons in cat lumbar spinal cord

Cited by 30 publications

References 61 publications

Intrathecal PACAP-38 causes increases in sympathetic nerve activity and heart rate but not blood pressure in the spontaneously hypertensive rat

Intrathecal PACAP-38 causes increases in sympathetic nerve activity and heart rate but not blood pressure in the spontaneously hypertensive rat

Differential regulation of the central neural cardiorespiratory system by metabotropic neurotransmitters

B�tzinger neurons project towards bulbospinal neurons in the rostral ventrolateral medulla of the rat

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