title: Comparison of baroreceptive to other afferent synaptic transmission to the medial solitary tract nucleus.
abstract: Cranial nerve visceral afferents enter the brain stem to synapse on neurons within the solitary tract nucleus (NTS). The broad heterogeneity of both visceral afferents and NTS neurons makes understanding afferent synaptic transmission particularly challenging. To study a specific subgroup of second-order neurons in medial NTS, we anterogradely labeled arterial baroreceptor afferents of the aortic depressor nerve (ADN) with lipophilic fluorescent tracer (i.e., ADN+) and measured synaptic responses to solitary tract (ST) activation recorded from dye-identified neurons in medial NTS in horizontal brain stem slices. Every ADN+ NTS neuron received constant-latency ST-evoked excitatory postsynaptic currents (EPSCs) (jitter < 192 micros, SD of latency). Stimulus-recruitment profiles showed single thresholds and no suprathreshold recruitment, findings consistent with EPSCs arising from a single, branched afferent axon. Frequency-dependent depression of ADN+ EPSCs averaged approximately 70% for five shocks at 50 Hz, but single-shock failure rates did not exceed 4%. Whether adjacent ADN- or those from unlabeled animals, other second-order NTS neurons (jitters < 200 micros) had ST transmission properties indistinguishable from ADN+. Capsaicin (CAP; 100 nM) blocked ST transmission in some neurons. CAP-sensitive ST-EPSCs were smaller and failed over five times more frequently than CAP-resistant responses, whether ADN+ or from unlabeled animals. Variance-mean analysis of ST-EPSCs suggested uniformly high probabilities for quantal glutamate release across second-order neurons. While amplitude differences may reflect different numbers of contacts, higher frequency-dependent failure rates in CAP-sensitive ST-EPSCs may arise from subtype-specific differences in afferent axon properties. Thus afferent transmission within medial NTS differed by axon class (e.g., CAP sensitive) but was indistinguishable by source of axon (e.g., baroreceptor vs. nonbaroreceptor).
authors.affiliation: Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon 97239-3098, USA. andresen.ohsu@gmail.com
authors.forename: Michael C
authors.initials: MC
authors.lastname: Andresen
authors.forename: James H
authors.initials: JH
authors.lastname: Peters
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001011:Aorta / Q000294:innervation*; D001369:Axons / Q000502:physiology; D002211:Capsaicin / Q000494:pharmacology; D003391:Cranial Nerves / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D005071:Evoked Potentials; D019706:Excitatory Postsynaptic Potentials; D018698:Glutamic Acid / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000502:physiology; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D013997:Time Factors
chemical_list: D018698:Glutamic Acid; D002211:Capsaicin
references.citation: J Neurophysiol. 2008 Apr;99(4):1712-22
references.pmid: 18272881
references.citation: J Neurosci Methods. 2002 Apr 15;115(2):157-67
references.pmid: 11992667
references.citation: Nat Rev Neurosci. 2008 Jan;9(1):11-25
references.pmid: 18073776
references.citation: J Physiol. 1982 Jan;322:337-52
references.pmid: 7069619
references.citation: Am J Physiol. 1998 Aug;275(2):H632-40
references.pmid: 9683453
references.citation: Proc Natl Acad Sci U S A. 1994 Oct 25;91(22):10380-3
references.pmid: 7937958
references.citation: Adv Second Messenger Phosphoprotein Res. 1994;29:235-60
references.pmid: 7848714
references.citation: J Appl Physiol (1985). 2006 Aug;101(2):618-27
references.pmid: 16645192
references.citation: J Neurophysiol. 2005 May;93(5):2530-40
references.pmid: 15615836
references.citation: Am J Physiol Regul Integr Comp Physiol. 2003 May;284(5):R1340-53
references.pmid: 12531785
references.citation: Am J Physiol. 1993 May;264(5 Pt 2):H1674-85
references.pmid: 8498579
references.citation: J Comp Neurol. 1993 Sep 8;335(2):163-72
references.pmid: 8227512
references.citation: J Physiol. 2004 Jan 1;554(Pt 1):175-93
references.pmid: 14678500
references.citation: J Neurosci. 2004 May 19;24(20):4709-17
references.pmid: 15152030
references.citation: J Physiol. 2003 Oct 15;552(Pt 2):547-59
references.pmid: 14561836
references.citation: Annu Rev Physiol. 2006;68:279-305
references.pmid: 16460274
references.citation: Eur J Neurosci. 1992 Oct;4(1):113-117
references.pmid: 12106447
references.citation: Neuron. 2008 Feb 7;57(3):420-31
references.pmid: 18255034
references.citation: Neuron. 2004 Jul 8;43(1):119-31
references.pmid: 15233922
references.citation: Am J Physiol. 1999 Sep;277(3):R748-56
references.pmid: 10484492
references.citation: Curr Protoc Neurosci. 2008 Jan;Appendix 4:Appendix 4B
references.pmid: 18428669
references.citation: Am J Physiol. 1996 Oct;271(4 Pt 2):R870-80
references.pmid: 8897976
references.citation: J Physiol. 2007 Jul 15;582(Pt 2):613-28
references.pmid: 17510187
references.citation: Q J Exp Physiol. 1981 Oct;66(4):391-404
references.pmid: 6914676
references.citation: J Neurosci. 2002 Sep 15;22(18):8222-9
references.pmid: 12223576
references.citation: J Neurophysiol. 1995 Oct;74(4):1518-28
references.pmid: 8989390
references.citation: Respir Physiol. 1995 Sep;101(3):219-30
references.pmid: 8606995
references.citation: J Neurophysiol. 1994 Jun;71(6):2338-58
references.pmid: 7523613
references.citation: J Neurosci. 2000 Mar 1;20(5):1904-11
references.pmid: 10684891
references.citation: Nat Neurosci. 2005 May;8(5):571-8
references.pmid: 15856065
references.citation: Nature. 2007 Dec 20;450(7173):1245-8
references.pmid: 18097412
references.citation: J Neurosci. 2006 Nov 15;26(46):11893-902
references.pmid: 17108163
references.citation: Brain Res. 1999 Feb 13;818(2):285-90
references.pmid: 10082814
references.citation: J Physiol. 1998 Oct 1;512 ( Pt 1):149-62
references.pmid: 9729625
references.citation: J Neurosci. 2004 Jun 16;24(24):5516-24
references.pmid: 15201324
references.citation: J Physiol. 1985 Mar;360:261-73
references.pmid: 3989716
references.citation: Development. 1987 Dec;101(4):697-713
references.pmid: 2460302
references.citation: J Neurosci. 2006 Jun 7;26(23):6131-42
references.pmid: 16763021
references.citation: J Neurophysiol. 1997 Dec;78(6):3198-209
references.pmid: 9405539
references.citation: J Neurophysiol. 1997 Jul;78(1):82-91
references.pmid: 9242263
references.citation: J Neurophysiol. 2007 Nov;98(5):3060-71
references.pmid: 17898143
references.citation: J Neurosci Methods. 2004 Aug 15;137(1):37-48
references.pmid: 15196825
references.citation: J Neurophysiol. 1988 Jun;59(6):1798-813
references.pmid: 3404205
references.citation: J Negat Results Biomed. 2006 May 18;5:6
references.pmid: 16709252
references.citation: J Neurophysiol. 2005 Dec;94(6):3849-59
references.pmid: 16293589
references.citation: J Physiol. 1986 Apr;373:63-86
references.pmid: 3746682
references.citation: Pain. 1983 Feb;15(2):109-30
references.pmid: 6189047
references.citation: J Neurophysiol. 1986 May;55(5):1076-90
references.pmid: 3012009
references.citation: J Neurosci. 2005 Apr 6;25(14):3578-85
references.pmid: 15814788
references.citation: J Neurosci. 2001 Oct 15;21(20):7889-900
references.pmid: 11588162
references.citation: J Physiol. 2005 Jan 15;562(Pt 2):535-51
references.pmid: 15539399
references.citation: Ann N Y Acad Sci. 2004 Jun;1018:71-5
references.pmid: 15240354
references.citation: J Neurosci Methods. 2007 Aug 15;164(1):75-85
references.pmid: 17512602
references.citation: J Appl Physiol Respir Environ Exerc Physiol. 1977 Mar;42(3):344-8
references.pmid: 838656
references.citation: J Neurosci. 2007 Nov 28;27(48):13292-302
references.pmid: 18045923
references.citation: Brain Res Bull. 1995;37(4):397-404
references.pmid: 7620913
references.citation: Neuroreport. 1999 Apr 26;10(6):1177-81
references.pmid: 10363920
references.citation: Trends Neurosci. 2000 Mar;23(3):105-13
references.pmid: 10675910
references.citation: Neuroscience. 2000;95(1):141-53
references.pmid: 10619470
references.citation: Front Neuroendocrinol. 2007 Apr;28(1):50-60
references.pmid: 17391741
references.citation: Brain Res. 1980 Apr 21;188(1):23-32
references.pmid: 6154500
references.citation: Am J Physiol. 1996 Dec;271(6 Pt 2):H2218-27
references.pmid: 8997277
references.citation: J Physiol. 1999 Oct 1;520 Pt 1:243-53
references.pmid: 10517815
references.citation: J Hypertens. 2002 Sep;20(9):1675-88
references.pmid: 12195099
references.citation: J Neurosci Methods. 2003 Dec 15;130(2):115-25
references.pmid: 14667541
references.citation: J Neurosci Methods. 2003 Dec 15;130(2):127-41
references.pmid: 14667542
references.citation: Science. 1987 May 22;236(4804):959-62
references.pmid: 3576212
references.citation: Neurosci Lett. 1983 Mar 28;36(1):37-42
references.pmid: 6856201
references.citation: Annu Rev Physiol. 1994;56:93-116
references.pmid: 7912060
references.citation: Braz J Med Biol Res. 2004 Apr;37(4):549-58
references.pmid: 15064818
references.citation: Brain Res Bull. 1981 May;6(5):393-8
references.pmid: 7248805
references.citation: Brain Res. 1992 May 29;581(2):339-43
references.pmid: 1382802
references.citation: J Neurophysiol. 2001 May;85(5):2213-23
references.pmid: 11353036
references.citation: J Neurophysiol. 1998 May;79(5):2365-73
references.pmid: 9582212
references.citation: Neurosci Lett. 2007 Jun 21;421(1):62-6
references.pmid: 17555875
references.citation: J Neurophysiol. 1985 Aug;54(2):245-60
references.pmid: 4031986
references.citation: J Auton Nerv Syst. 1995 Jul 14;54(1):16-26
references.pmid: 7594207