Enhancement of spontaneous baroreflex by antisense c-fosoligonucleotide treatment in the NTS of the rat

Abstract

We evaluated the hypothesis that basal Fos protein at the nucleus tractus solitarii (NTS), the primary terminal site for baroreceptor afferents, exerts a tonic inhibitory modulation on the spontaneous baroreceptor reflex (BRR) control machinery, which is responsible for beat-to-beat regulation of resting systemic arterial pressure (SAP). In adult male Sprague-Dawley rats anesthetized and maintained with pentobarbital sodium, microinjection bilaterally into the caudal NTS of a 15-mer antisense oligonucleotide that targets against the initiation codon of c- fosmRNA (5′-129 to 143-3′) significantly enhanced the spontaneous BRR response, as determined by transfer function analysis of SAP and heart rate signals. The same treatment also diminished baseline Fos-like immunoreactivity in the absence of acute cardiovascular perturbation. Control treatments with artificial cerebrospinal fluid, sense cDNA, or antisense oligonucleotides that either target against a different site of the c- fos mRNA (5′-135 to 149-3′) or with three mismatched nucleotides in the antisense sequence, were ineffective. These observations support the notion that, under minimal cardiovascular perturbation, basal expression of Fos protein in the NTS may represent an early step in the cascade of intracellular events that leads to long-term inhibitory modulation of beat-to-beat baroreflex control of blood pressure.

Augmented Upregulation by c- fos of Angiotensin Subtype 1 Receptor in Nucleus Tractus Solitarii of Spontaneously Hypertensive Rats

“…Three 15-mer phosphorothioated c-fos oligonucleotides (Quality System, Taipei, Taiwan) were used, [22][23][24] including a key antisense oligonucleotide (ASON1) that targets against a region of the c-fos mRNA that flanks the initiation codon (5Ј-129 to 143-3Ј) and a corresponding sense (SON) and a scrambled (ASON2) c-fos oligonucleotide. Each oligonucleotide was microinjected bilaterally, at a volume of 50 nL, into the NTS (nϭ25 to 30 animals per group) under pentobarbital anesthesia (50 mg/kg IP) 24 hours before the experimental sessions.…”

“…[21][22][23][24] A rabbit polyclonal anti-Fos antiserum (sc-52, 1:4000; Santa Cruz) was used, and Fos-like immunoreactivity (Fos-LI) was visualized by a Vectastain ABC kit (Vector). As a routine, sections from both SHR and WKY that received the same treatment schedule were processed together.…”

“…The criterion for identification of Fos-LI was a distinctly stained nucleus, and the number of NTS neurons that displayed Fos-LI was quantified as reported previously. [21][22][23][24] Double immunohistochemical staining for Fos-LI and AT1R or AT2R was processed in some experiments as described. 29 In brief, sections were similarly processed for Fos-LI, using a polyclonal goat anti-Fos antiserum (sc-52G, 1:4000; Santa Cruz) and visualized by a Vectastain ABC peroxidase kit with nickel intensification.…”

“…Baroreceptor activation resulted in Fos expression in the commissural, medial and dorsomedial subnuclei of NTS 19,[21][22][23][24]26,29 of SHR and WKY (Figure 2). Whereas a majority of NTS neurons that showed Fos-LI was double labeled for AT1R (Figures 2A and 2B), fewer Fos-positive neurons in the NTS were immunoreactive to AT2R (Figures 2C and 2D).…”

Inhibition of Baroreflex by Angiotensin II via Fos Expression in Nucleus Tractus Solitarii of the Rat

“…s the principal terminal site of the primary baroreceptor afferents, 1 the caudal nucleus tractus solitarii (NTS) in the medulla oblongata has become a major focus in recent studies [2][3][4][5][6][7][8][9] on the anatomic and temporal specificity of Fos expression after cardiovascular perturbations. In terms of function, workers at our laboratory reported that both basal 6 and induced 4 Fos expression in the caudal NTS may represent an early step in the cascade of intracellular events that leads to long-term inhibitory modulation of baroreceptor reflex (BRR) response.…”