Distribution of fos-like immunoreactivity in the rat brain following intravenous lipopolysaccharide administration

Abstract

The central nervous system, particularly the hypothalamus, is intimately involved in the coordination of various aspects of the inflammatory response, including the generation of fever. We used intravenous injections of bacterial cell wall lipopolysaccharide (LPS; 5 or 125 micrograms/kg) to stimulate the acute phase response and mapped the resultant distribution of Fos-like immunoreactivity in the rat brain. In addition, we compared the patterns of Fos distribution with the thermoregulatory responses elicited by the LPS. Administration of LPS resulted in a dose- and time-dependent pattern of Fos-like immunoreactivity throughout the rat brain consistent with a coordinated autonomic, endocrine, and behavioral response to the LPS challenge that was most pronounced 2 hours following injection. Specifically, Fos-like immunoreactivity was observed in key autonomic regulatory nuclear groups, including the insular and prelimbic cortices, paraventricular hypothalamic nucleus, parabrachial nucleus, nucleus of the solitary tract, and the rostral and caudal levels of the ventrolateral medulla. In addition, a significant sustained elevation of Fos-like immunoreactivity was observed in a cell group adjacent to the organum vasculosum of the lamina terminalis, which we termed the ventromedial preoptic area. This sustained elevation of Fos-like immunoreactivity coupled with the alterations in body temperature elicited by LPS leads us to hypothesize that the ventromedial preoptic area may be a key site for the initiation of fever during endotoxemia.

Serotonin Activates the Hypothalamic-Pituitary-Adrenal Axis via Serotonin 2C Receptor Stimulation

“…Four experimental groups were used: (1) C57BL/6 mice treated at the onset of the light cycle with pyrogen-free 0.9% saline or the high-affinity 5-HT 2C R agonist m-chlorophenylpiperazine (mCPP) (2.5 or 5.0 mg/kg, i.p. ; n ϭ 3-4 per dose); (2) rats fitted with a catheter in the femoral vein as described previously (Elmquist et al, 1996;Elias et al, 1998) 5-7 d before treatment with saline, mCPP (0.5, 2.5, or 5.0 mg/kg, i.v. ), or the 5-HT reuptake inhibitor/5-HT-stimulated release compound D-fenfluramine (D-fen; 0.1, 1.0, or 2.0 mg/kg, i.v.)…”

“…at the onset of the light cycle (n ϭ 3-5 per dose); (3) rats treated during the light cycle with 40 g of colchicine (Sigma-Aldrich, St. Louis, MO) in 10 l of pyrogen-free 0.9% saline infused into the lateral ventricle to enhance CRH visualization (n ϭ 5); and (4) untreated 5-HT 2C R knock-out and wild-type mice perfused during the light cycle for hypothalamic neuropeptide expression analysis (n ϭ 8 -9 per genotype). Using methods standard in our laboratory (Elmquist et al, 1996;Elias et al, 1998;Liu et al, 2003;Heisler et al, 2006), brain tissue was prepared through transcardial perfusion with 0.9% saline and then 10% neutral buffered formalin (Sigma-Aldrich) under chloral hydrate anesthesia (350 mg/kg, i.p.) 2 h after saline, mCPP, or D-fen treatment and 36 -48 h after colchicine treatment.…”

“…Brain tissue was processed for single-label free-floating in situ hybridization histochemistry (ISHH), single-label immunohistochemistry (IHC) (Elmquist et al, 1996;Elias et al, 1998;Heisler et al, 2002;Yamamoto et al, 2003), or dual-label ISHH and IHC using methods detailed previously Heisler et al, 2006). ISHH was performed using an antisense 35 S-labeled CRH , 35 S-labeled 5-HT 2C R (Molineaux et al, 1989), 35 S-labeled cocaine-and amphetamine-regulated transcript (CART) (Couceyro et al, 1997), 35 Slabeled pro-opiomelanocortin (POMC) (Cheung et al, 1997), or 35 Slabeled melanin-concentrating hormone (MCH) (Qu et al, 1996) riboprobe generated from cDNA templates by in vitro transcription with a T3 (5-HT 2C R and CART), T7 (CRH), or SP6 (POMC and MCH) polymerase, according to the manufacturer's protocol (Promega, Madison, WI).…”

Development of Posttraumatic Hyperthermia after Traumatic Brain Injury in Rats is Associated with Increased Periventricular Inflammation

“…According to Elmquist et al (1996) and Saper (1998), regional centers within the hypothalamus involved in the febrile response to an immune stimulus include the ventromedial preoptic nucleus (VMPO) and the paraventricular hypothalamic nucleus (PVN) (Elmquist et al, 1996;Saper, 1998). The anterior perifornical nucleus (APF) receives significant input from the VMPO and is also involved in the febrile immune response via feedback to the PVN (Saper, 1998).…”

Activation of the Locus Coeruleus After Amygdaloid Kindling

“…The brains were removed and cut in a freezing microtome into four series of 30-mm-thick sections. Immunohistochemistry for Fos protein was performed by using an immunoperoxidase method similar to that previously described (10 for 20 min; 3% normal goat serum and 0.25% Triton X-100 in PBS (PGT) for 1 h; anti-Fos-antibody (Oncogene, lot Ab-5; 1:100,000) for 48 h; biotinylated goat anti-rabbit immunoglobulin G (IgG; Vector; 1 :600 in PGT diluent) for 1 h at room temperature; and avidinbiotin complex reagent for 1 h (Vector Elite Kit; 1:200 in PBS). After rinsing in PBS, the sections were developed in 3,3'-diaminobenzidine (Sigma; 0.2 mg/ml), 0.02% cobalt chloride (Fisher Scientific), and 0.01 % hydrogen peroxide for 5-10 min.…”