Medullary lateral tegmental field: an important synaptic relay in the baroreceptor reflex pathway of the cat.
This study was designed to test the hypothesis that the medullary lateral tegmental field (LTF) is an important synaptic relay in the baroreceptor reflex pathway controlling sympathetic nerve discharge (SND) of urethan-anesthetized cats. We determined the effects of blockade of excitatory amino acid-mediated neurotransmission in the LTF on three indexes of baroreceptor reflex function: cardiac-related power in SND, strength of linear correlation (coherence value) of SND to the arterial pulse (AP), and inhibition of SND during increased arterial pressure produced by abrupt obstruction of the abdominal aorta. Bilateral microinjection of D-(-)-2-amino-5-phosphonopentanoic acid, an N-methyl-D-aspartate (NMDA) receptor antagonist, abolished cardiac-related power and coherence of SND to the AP, and it prevented inhibition of SND during aortic obstruction. These data support the view that NMDA receptor-mediated neurotransmission in the LTF is critical for baroreceptor reflex control of SND. Bilateral microinjection of 1,2, 3,4-tetrahydro-6-nitro-2,3-dioxobenzo-[f]-quinoxaline-7-sulfonamid e, a non-NMDA receptor antagonist, decreased cardiac-related power and total power in the 0- to 6-Hz band of SND; however, the AP-SND coherence value remained high, and inhibition of SND during aortic obstruction was preserved. These data imply that non-NMDA receptor-mediated neurotransmission in the LTF is involved in setting the level of excitatory drive to sympathetic nerves.
Orer
H S
HS
Department of Pharmacology, Michigan State University, East Lansing, Michigan 48824, USA.
Barman
S M
SM
Gebber
G L
GL
Sykes
S M
SM
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D001931:Brain Mapping; D002415:Cats; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006329:Heart Conduction System / Q000187:drug effects / Q000502:physiology; D008526:Medulla Oblongata / Q000502:physiology*; D008845:Microinjections; D011810:Quinoxalines / Q000494:pharmacology; D017552:Solitary Nucleus / Q000502:physiology; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology; D013569:Synapses / Q000502:physiology*; D013681:Tegmentum Mesencephali / Q000502:physiology*
D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D015763:2-Amino-5-phosphonovalerate