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Critical role of B3 serotonergic cells in baroreflex inhibition during the defense reaction triggered by dorsal periaqueductal gray stimulation
Author(s) -
Bernard JeanFrançois,
Netzer Florence,
Gau Rémi,
Hamon Michel,
Laguzzi Raùl,
SévozCouche Caroline
Publication year - 2007
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.21532
Subject(s) - serotonergic , muscimol , periaqueductal gray , microinjection , dorsal raphe nucleus , stimulation , neuroscience , agonist , baroreflex , nucleus raphe magnus , biology , inhibitory postsynaptic potential , raphe nuclei , pharmacology , endocrinology , medicine , receptor , serotonin , central nervous system , midbrain , heart rate , blood pressure
The present study was designed to identify the serotonergic pathway causing baroreflex inhibition associated with the defense reaction in rats. Under conditions that produce physiological responses typical of the defense reaction, electrical stimulation of the dorsal periaqueductal gray (dPAG) was found to double c‐Fos immunoreactive serotonergic neurons within the mid‐rostrocaudal extent of the B3 group (which comprises the raphe magnus and the lateral paragigantocellular reticular nuclei) in anesthetized rats. Local blockade of neuronal activity by microinjection of muscimol (a GABA A receptor agonist) directly into the B3 region prevented the inhibitory effect of dPAG activation on the cardiac baroreflex. Conversely, neuron activation by local application of D,L‐homocysteic acid into B3 region caused baroreflex inhibition that was suppressed by microinjection of granisetron (a 5‐HT 3 antagonist) into the nucleus tractus solitarius. These results show that activation of serotonergic cells in the mid‐portion of B3 group is critical to trigger baroreflex inhibition occurring during the defense reaction evoked by dPAG stimulation. J. Comp. Neurol. 506:108–121, 2008. © 2007 Wiley‐Liss, Inc.