Glycinergic inputs to cardiac vagal neurons in the nucleus ambiguus are inhibited by nociceptin and mu-selective opioids

Journal of Neurophysiology
Priya VenkatesanDavid Mendelowitz

Abstract

Most parasympathetic regulation of heart rate originates from preganglionic cardiac vagal neurons within the nucleus ambiguus. Little is known regarding the modulation of glycinergic transmission to these neurons. However, the presence of mu-opioid receptors and opioid-receptor-like (ORL1) receptors within the ambiguus, together with the presence of endogenous ligands for both receptor types in the same area, suggests opioids may modulate synaptic transmission to cardiac vagal neurons. This study therefore examined the effects of endomorphin-1 and endomorphin-2 (the mu-selective endogenous peptides), DAMGO (a synthetic, mu-selective agonist), and nociceptin (the ORL1-selective endogenous peptide) on spontaneous glycinergic inhibitory postsynaptic currents (IPSCs) in rat cardiac parasympathetic neurons. All four of the opioids used in this study decreased spontaneous IPSCs. At concentrations of 100 microM, the amplitude of the IPSCs was reduced significantly by nociceptin (-56.6%), DAMGO (-46.5%), endomorphin-1 (-45.1%), and endomorphin-2 (-26%). IPSC frequency was also significantly reduced by nociceptin (-61.1%), DAMGO (-69.9%), and endomorphin-1 (-40.8%) but not endomorphin-2. Lower concentrations of nociceptin and DAMGO (10-...Continue Reading

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Citations

Apr 6, 2004·Brain Research·Kathleen J S GriffioenDavid Mendelowitz
Sep 29, 2012·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Vineet C ChitravanshiHreday N Sapru
May 11, 2010·Drugs & Aging·Howard Smith, Patricia Bruckenthal
Jul 8, 2005·Brain Research·Vineet C Chitravanshi, Hreday N Sapru
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