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Substance P-immunoreactive axons synapse on barosensitive neurons in rat nucleus tractus solitarius
Abstracts
I-3C-02 Substance P-immunoreactive axons synapse on barosensitive neurons in rat nucleus tractus solitarius Ida J. Llewellyn-Smith a, Daniel O. Kellett b, Gareth A. Jones b, David Jordan b a Centre for Neuroscience, Flinders University, Flinders, Australia b Department of Physiology, University College London, London, United Kingdom
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Betty Exintaris a, Anupa Dey a , Dan-Thanh Nguyen a, Snezana Kusljic a, Rick Lang b a Department of Pharmaceutical Pharmacology, Victorian College of Pharmacy, Monash University, Australia b Department of Physiology, Monash University, Australia Introduction and aim We have previously reported the presence of distinct electrical activities and cell types in the guinea-pig prostate and speculated as to their functional roles. We believe that a specialised group of c-Kit immunoreactive prostatic interstitial cells (PIC) that lie between the glandular epithelium and smooth muscle stroma have a similar role to intestinal interstitial cells of Cajal (ICC), generating the pacemaker signal that manifests as slow wave activity and ensuing contractility in the smooth muscles cells of the guinea-pig prostate (1). The aim of this study was to characterise the spontaneous electrical activity in prostates of younger and older guinea-pigs.
The nucleus tractus solitarius (NTS) in the dorsal medulla contains neurons that receive baroreceptor input and is a major site for central regulation of blood pressure. One transmitter that affects cardiovascular control through the NTS is substance P (SP). SP excites NTS neurons and is released by stimulation of aortic afferents, leading to an alteration in baroreflex sensitivity. Although pharmacological effects of SP have been demonstrated, it is not yet known whether axons containing SP directly innervate barosensitive NTS neurons. We used two approaches to answer this question. In one series of experiments, we evoked Fos expression in awake rats by intravenous infusion of phenylephrine (PE) to increase blood pressure to 125–130% of baseline. Control rats were infused with saline. Sections of perfused medulla were immunostained with peroxidase to reveal Fos plus SP and processed for light or electron microscopy. In a second series of experiments, we juxtacellularly labelled with Neurobiotin NTS neurons that responded to vagal or aortic nerve stimulation, detected the filled neurons with avidinperoxidase and localized SP immunohistochemically. After PE infusion, strong Fos-immunoreactivity occurred in the nuclei of many neurons in the baroreceptor region of caudal NTS, where aortic afferents terminate. Few Fosimmunoreactive neurons were present in the NTS of control rats. At the light microscope level, neurons with Fos-immunoreactive nuclei were found to lie within a network of varicose SP-immunoreactive axons and terminals positive for SP formed close appositions on all juxtacellularly labelled NTS neurons. These suggestions of a direct SP input to barosensitive NTS neurons were confirmed ultrastructurally by the occurrence of synapses from SP-immunoreactive axon terminals onto the cell bodies of Fos-immunoreactive NTS neurons. The presence of axosomatic synapses on barosensitive NTS neurons suggests that the activation of SP-containing inputs in the NTS could have powerful effects on cardiovascular responses. Supported by NH & MRC Australia, Wellcome Trust UK.
Four types of electrical activity were recorded in the guinea-pig prostate: slow waves, pacemaker potentials, standard transient depolarisations (STDs) and spike potentials. In young animals the majority of electrical recordings comprised of slow wave activity (84%) (n = 38). Pacemaker activity was recorded in 7% of cells; the remaining cells exhibited spike potential discharge (9%). In contrast, the most prevalent electrical activity recorded in the older prostates (54%) was spike potentials (n =22). Slow wave activity was recorded in 32% of cells (n = 13), STDs comprised 14% of all electrical recordings and pacemaker potentials were not observed. Confocal microscopic examinations of the prostate revealed a network of c-Kit-immunoreactive PIC lying predominantly between the smooth muscle stroma and the epithelial-lined lumen of the young guinea-pig prostate. Preliminary results indicate that PIC, but not smooth muscle cells, appear to communicate to each other via connexin 43, as connexin 43 immunostaining was clearly expressed in the PIC layer only.
doi:10.1016/j.autneu.2007.06.088
Conclusion
I-3C-03 Spontaneous activity in the prostate gland
With age, there is a change in the proportion of cells exhibiting the different electrical waveforms. This could be partly explained by a change in the distribution of c-Kit
Methods Prostates were removed from guinea-pigs (300–1200 g) killed humanely. Electrical activity from the guinea-pig prostate was recorded using intracellular microelectrodes. Results
I-3C-02 Substance P-immunoreactive axons synapse on barosensitive neurons in rat nucleus tractus solitarius Ida J. Llewellyn-Smith a, Daniel O. Kellett b, Gareth A. Jones b, David Jordan b a Centre for Neuroscience, Flinders University, Flinders, Australia b Department of Physiology, University College London, London, United Kingdom
59
Betty Exintaris a, Anupa Dey a , Dan-Thanh Nguyen a, Snezana Kusljic a, Rick Lang b a Department of Pharmaceutical Pharmacology, Victorian College of Pharmacy, Monash University, Australia b Department of Physiology, Monash University, Australia Introduction and aim We have previously reported the presence of distinct electrical activities and cell types in the guinea-pig prostate and speculated as to their functional roles. We believe that a specialised group of c-Kit immunoreactive prostatic interstitial cells (PIC) that lie between the glandular epithelium and smooth muscle stroma have a similar role to intestinal interstitial cells of Cajal (ICC), generating the pacemaker signal that manifests as slow wave activity and ensuing contractility in the smooth muscles cells of the guinea-pig prostate (1). The aim of this study was to characterise the spontaneous electrical activity in prostates of younger and older guinea-pigs.
The nucleus tractus solitarius (NTS) in the dorsal medulla contains neurons that receive baroreceptor input and is a major site for central regulation of blood pressure. One transmitter that affects cardiovascular control through the NTS is substance P (SP). SP excites NTS neurons and is released by stimulation of aortic afferents, leading to an alteration in baroreflex sensitivity. Although pharmacological effects of SP have been demonstrated, it is not yet known whether axons containing SP directly innervate barosensitive NTS neurons. We used two approaches to answer this question. In one series of experiments, we evoked Fos expression in awake rats by intravenous infusion of phenylephrine (PE) to increase blood pressure to 125–130% of baseline. Control rats were infused with saline. Sections of perfused medulla were immunostained with peroxidase to reveal Fos plus SP and processed for light or electron microscopy. In a second series of experiments, we juxtacellularly labelled with Neurobiotin NTS neurons that responded to vagal or aortic nerve stimulation, detected the filled neurons with avidinperoxidase and localized SP immunohistochemically. After PE infusion, strong Fos-immunoreactivity occurred in the nuclei of many neurons in the baroreceptor region of caudal NTS, where aortic afferents terminate. Few Fosimmunoreactive neurons were present in the NTS of control rats. At the light microscope level, neurons with Fos-immunoreactive nuclei were found to lie within a network of varicose SP-immunoreactive axons and terminals positive for SP formed close appositions on all juxtacellularly labelled NTS neurons. These suggestions of a direct SP input to barosensitive NTS neurons were confirmed ultrastructurally by the occurrence of synapses from SP-immunoreactive axon terminals onto the cell bodies of Fos-immunoreactive NTS neurons. The presence of axosomatic synapses on barosensitive NTS neurons suggests that the activation of SP-containing inputs in the NTS could have powerful effects on cardiovascular responses. Supported by NH & MRC Australia, Wellcome Trust UK.
Four types of electrical activity were recorded in the guinea-pig prostate: slow waves, pacemaker potentials, standard transient depolarisations (STDs) and spike potentials. In young animals the majority of electrical recordings comprised of slow wave activity (84%) (n = 38). Pacemaker activity was recorded in 7% of cells; the remaining cells exhibited spike potential discharge (9%). In contrast, the most prevalent electrical activity recorded in the older prostates (54%) was spike potentials (n =22). Slow wave activity was recorded in 32% of cells (n = 13), STDs comprised 14% of all electrical recordings and pacemaker potentials were not observed. Confocal microscopic examinations of the prostate revealed a network of c-Kit-immunoreactive PIC lying predominantly between the smooth muscle stroma and the epithelial-lined lumen of the young guinea-pig prostate. Preliminary results indicate that PIC, but not smooth muscle cells, appear to communicate to each other via connexin 43, as connexin 43 immunostaining was clearly expressed in the PIC layer only.
doi:10.1016/j.autneu.2007.06.088
Conclusion
I-3C-03 Spontaneous activity in the prostate gland
With age, there is a change in the proportion of cells exhibiting the different electrical waveforms. This could be partly explained by a change in the distribution of c-Kit
Methods Prostates were removed from guinea-pigs (300–1200 g) killed humanely. Electrical activity from the guinea-pig prostate was recorded using intracellular microelectrodes. Results