Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, PC20
Neuropeptide Y in the rat central catecholaminergic system
J. Kourtesis1, P. Verkade1, A. G. Teschemacher1
1. University of Bristol, Bristol, United Kingdom.
Neuropeptide Y (NPY) is a known co-transmitter of noradrenaline in sympathetic neurones and is involved in cardiovascular homoeostasis in the periphery. NPY has also been implicated in blood pressure control by the brain, in particular at the level of the nucleus of the solitary tract (NTS) (Grundemar et al 1991; Smith et al 1992). Previous evidence has suggested distinct roles in blood pressure control for different catecholaminergic (CAergic) cell groups in the brainstem (see Kasparov & Teschemacher, 2008), but to which extent NPY and CAergic systems overlap is not known. In this study, we aimed to investigate co-transmission of NPY with noradrenaline and adrenaline in the central nervous system. Experiments were conducted in accordance with the UK Animals (Scientific Procedures) Act 1986 and associated guidelines. Wistar adult male rats (n = 3) were terminally anaesthetised using pentobarbital (400mg/ kg i.p.) and subsequently perfusion-fixed transcardially with 4% paraformaldehyde. 40 μm sections of the brainstem were fluorescently double-labelled with antibodies against dopamine-b-hydroxylase (DbH; Abcam) and NPY (kind gift from Dr. Grouzmann, Lausanne, Switzerland). Alexa Fluor 594- and Alexa Fluor 488-conjugated secondary antibodies were used, respectively. Images were acquired with a confocal laser scanning microscope (Leica SP1). Approximately 3500 NPY- and 8500 DbH-immunoreactive cells were identified per rat and co-localisation was determined as percentage (± st.dev.) of DbH-immunoreactive cell bodies which labelled positive for NPY. We found co-localisation of DbH and NPY in A2 cells in the NTS, A1 cells in the caudal ventro-lateral medulla (CVLM), and C1 cells in the rostral ventro-lateral medulla (RVLM). Interestingly, 81% (± 4.5%) of DbH-positive A2 cells in the rostral NTS also contained NPY but only 23% (± 0.9%) of A2 cells co-expressed NPY in the caudal NTS. In the CVLM, 88% (± 3.0%) of DbH-positive cells also contained NPY. In the RVLM, 81% (± 1.7%) of DbH-positive cells were NPY-immunoreactive. In contrast, there was hardly any co-localisation (2% ± 0.1%) of NPY in DbH-positive A6 cells in the locus coeruleus (LC). Conversely, the majority (>85%) of NPY-positive cells in RVLM and CVLM areas contained DbH, while in the NTS only approximately 65% of NPY-expressing cells were CAergic. Further studies to (i) characterise co-localisation at the ultra-structural level and (ii) comparison of co-expression between Wistar and spontaneously hypertensive rats are ongoing. These data suggest that catecholamines and NPY may act as co-transmitters in central cardiovascular control.
Where applicable, experiments conform with Society ethical requirements