Modulation of AMPA receptors by cAMP-dependent protein kinase in preBotzinger complex inspiratory neurons regulates respiratory rhythm in the rat.

Authors: Shao, XM  Ge, Q  Feldman, JL 
Citation: Shao XM, etal., J Physiol. 2003 Mar 1;547(Pt 2):543-53. Epub 2003 Jan 24.
Pubmed: (View Article at PubMed) PMID:12562968
DOI: Full-text: DOI:10.1113/jphysiol.2002.031005

We hypothesize that phosphorylation of AMPA receptors or associated synaptic proteins modulates the excitability of respiratory neurons in the preBotzinger Complex (preBotC), affecting respiratory rhythm. Using neonatal rat medullary slices that spontaneously generate respiratory rhythm, we examined the role of the cAMP-PKA pathway (PKA: cAMP-dependent protein kinase) in modulating glutamatergic synaptic transmission, the excitability of inspiratory neurons in the preBotC and respiratory rhythm. Microinjection of forskolin, an activator of adenylate cyclase, into the preBotC with or without the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), decreased the period (increased the frequency) of respiratory-related rhythmic motor output in the hypoglossal nerve (XIIn) to 84 % (without IBMX) and to 72 % (with IBMX) of the pre-injection baseline. In the presence of MK-801, a non-competitive NMDA receptor antagonist, microinjection of forskolin plus IBMX decreased the period to 66 % of baseline levels. Microinjection of Rp-adenosine 3',5'-cyclic monophosphothioate (Rp-cAMPS), a PKA inhibitor, increased the period to 145 % of baseline levels. Concurrent microinjection of Rp-cAMPS and forskolin had no effect on the period. Bath application of 7beta-deacetyl-7beta-[gamma-(morpholino)butyryl]-forskolin hydrochloride (7Db-forskolin, a water-soluble derivative of forskolin): (1) decreased the period to 67 % of baseline levels without affecting the amplitude of integrated XIIn inspiratory discharge, (2) induced a tonic inward current of 29 pA and enhanced inspiratory drive current (the amplitude increased to 183 % and the integral increased to 184 % of baseline) in voltage-clamped (holding potential = -60 mV) preBotC inspiratory neurons and (3) increased the frequency to 195 % and amplitude to 118 % of spontaneous excitatory postsynaptic currents (sEPSCs) during expiratory periods. Dideoxy-forskolin did not have these effects. Intracellular perfusion with the catalytic subunit of PKA (cPKA) into preBotC inspiratory neurons progressively enhanced inspiratory drive currents and, in the presence of TTX, increased the inward currents induced by local ejection of AMPA; the latter currents were blocked by 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulphonamide (NBQX, an AMPA/kainate receptor antagonist). The effects of cPKA were blocked by co-application of PKA inhibitor (6-22) amide (PKI). These results suggest that phosphorylation of postsynaptic AMPA receptors through the cAMP-PKA pathway modulates both tonic and phasic excitatory amino acid synaptic transmission and excitability of inspiratory neurons in the preBotC and, therefore, regulates respiratory rhythm. Moreover, the basal level of endogenous PKA activity appears to be a determinant of resting respiratory frequency.

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CRRD Object Information
CRRD ID: 1580676
Created: 2006-08-21
Species: All species
Last Modified: 2006-08-21
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.