P2Y1 Receptor Modulation of the Pre-Botzinger Complex Inspiratory Rhythm Generating Network In Vitro

Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 01/2007; 27(5):993-1005. DOI: 10.1523/JNEUROSCI.3948-06.2007
Source: PubMed


ATP is released during hypoxia from the ventrolateral medulla (VLM) and activates purinergic P2 receptors (P2Rs) at unknown loci to offset the secondary hypoxic depression of breathing. In this study, we used rhythmically active medullary slices from neonatal rat to map, in relation to anatomical and molecular markers of the pre-Bötzinger complex (preBötC) (a proposed site of rhythm generation), the effects of ATP on respiratory rhythm and identify the P2R subtypes responsible for these actions. Unilateral microinjections of ATP in a three-dimensional grid within the VLM revealed a "hotspot" where ATP (0.1 mM) evoked a rapid 2.2 +/- 0.1-fold increase in inspiratory frequency followed by a brief reduction to 0.83 +/- 0.02 of baseline. The hotspot was identified as the preBötC based on histology, overlap of injection sites with NK1R immunolabeling, and potentiation or inhibition of respiratory frequency by SP ([Sar9-Met(O2)11]-substance P) or DAMGO ([D-Ala2,N-MePhe4,Gly-ol5]-enkephalin), respectively. The relative potency of P2R agonists [2MeSADP (2-methylthioadenosine 5'-diphosphate) approximately = 2MeSATP (2-methylthioadenosine 5'-triphosphate) approximately = ATPgammas (adenosine 5'-[gamma-thio]triphosphate tetralithium salt) approximately = ATP > UTP approximately = alphabeta meATP (alpha,beta-methylene-adenosine 5'-triphosphate)] and attenuation of the ATP response by MRS2179 (2'-deoxy-N6-methyladenosine-3',5'-bisphosphate) (P2Y1 antagonist) indicate that the excitation is mediated by P2Y1Rs. The post-ATP inhibition, which was never observed in response to ATPgammas, is dependent on ATP hydrolysis. These data establish in neonatal rats that respiratory rhythm generating networks in the preBötC are exquisitely sensitive to P2Y1R activation, and suggest a role for P2Y1Rs in respiratory motor control, particularly in the P2R excitation of rhythm that occurs during hypoxia.

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Available from: Dean M Robinson, Nov 11, 2015
    • "Adenosine-mediated modulation has been well studied in the brain stem circuitry controlling mammalian respiration. Within these motor control circuits, glial-derived adenosine produces tonic depressive effects in rodents that are strongest at fetal stages (Herlenius and Lagercrantz 1999; Huxtable et al. 2010; Kawai et al. 1995; Lorier et al. 2007; Mironov et al. 1999; Schmidt et al. 1995). In addition to modulating respiratory frequency, presumably via actions on rhythm-generating neurons of the medullary pre-Bötzinger complex, adenosine also modulates the intensity of respiration-related output generated by motoneurons (Funk et al. 1997; Miles et al. 2002). "
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    • "Thus, LC purinergic signaling appears to play a role in the CO2 drive to breathe, specifically through the activation of P2 receptors, accelerating the ventilatory response to hypercapnia. This observation was probably due to P2X activation of noradrenergic neurons, triggering further NA and ATP release which in turn activate rhythm-generating circuits and medullary respiratory neurons in one or more of the following brainstem nuclei: RTN, RVLM, prepositus hypoglossi nucleus, and NTS (Aston-Jones et al., 1986, 1991b; Astier et al., 1990; Pieribone and Aston-Jones, 1991; Vulchanova et al., 1997; Llewellyn-Smith and Burnstock, 1998; Kanjhan et al., 1999; Thomas and Spyer, 2000; Yao et al., 2000; Gourine et al., 2003; Lorier et al., 2007, 2008; Huxtable et al., 2009). "
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    • "ATP excites the preBötC in vitro in rats (Huxtable et al., 2009; Zwicker et al., 2011) through the activation of P2Y-receptors (Lorier et al., 2007; Huxtable et al., 2009). Interestingly, blockade of endogenous activation of P2-receptors with suramin reduced inspiratory frequency in the slice preparation, while Cu2+, an allosteric modulator of purinergic receptors, produced the opposite effect (Lorier et al., 2007, 2008). "
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