Comparison between two rat sympathetic pathways activated in cold defense

2006 ◽  
Vol 291 (3) ◽  
pp. R589-R595 ◽  
Author(s):  
Youichirou Ootsuka ◽  
Robin M. McAllen
Keyword(s):  
Cold Water ◽  
Relative Sensitivity ◽  
Sympathetic Nerves ◽  
Defense Responses ◽  
Interscapular Brown Adipose Tissue ◽  
Brain Circuits ◽  
Brown Adipose ◽  
Skin Cooling ◽  
Trunk Skin ◽  
Coherence Spectrum

In cold defense and fever, activity increases in sympathetic nerves supplying both tail vessels and interscapular brown adipose tissue (iBAT). These mediate cutaneous vasoconstrictor and thermogenic responses, respectively, and both depend upon neurons in the rostral medullary raphé. To examine the commonality of brain circuits driving these two outflows, sympathetic nerve activity (SNA) was recorded simultaneously from sympathetic fibers in the ventral tail artery (tail SNA) and the nerve to iBAT (iBAT SNA) in urethane-anesthetized rats. From a warm baseline, cold-defense responses were evoked by intermittently circulating cold water through a water jacket around the animal's shaved trunk. Repeated episodes of trunk skin cooling decreased core (rectal) temperature. The threshold skin temperature to activate iBAT SNA was 37.3 ± 0.5°C ( n = 7), significantly lower than that to activate tail SNA (40.1 ± 0.4°C; P < 0.01, n = 7). A fall in core temperature always strongly activated tail SNA (threshold 38.3 ± 0.2°C, n = 7), but its effect on iBAT SNA was absent (2 of 7 rats) or weak (threshold 36.9 ± 0.1°C, n = 5). The relative sensitivity to core vs. skin cooling (K-ratio) was significantly greater for tail SNA than for iBAT SNA. Spectral analysis of paired recordings showed significant coherence between tail SNA and iBAT SNA only at 1.0 ± 0.1 Hz. The coherence was due entirely to the modulation of both signals by the ventilatory cycle because it disappeared when the coherence spectrum was partialized with respect to airway pressure. These findings indicate that independent central pathways drive cutaneous vasoconstrictor and thermogenic sympathetic pathways during cold defense.

Lateral hypothalamus and sympathetic firing rate

1988 ◽  
Vol 255 (3) ◽  
pp. R507-R512 ◽  
Author(s):  
T. Sakaguchi ◽  
M. Takahashi ◽  
G. A. Bray
Keyword(s):  
Firing Rate ◽  
Lateral Hypothalamus ◽  
Sympathetic Nerves ◽  
Hypothalamic Area ◽  
Interscapular Brown Adipose Tissue ◽  
Gold Thioglucose ◽  
Brown Adipose ◽  
Bilateral Lesions ◽  
Dose Dependent ◽  
Lowered Body

Measurements of sympathetic firing rate have been made after the acute microinjection of glucose or insulin into the lateral hypothalamic area as well as after ablation of this area with locally injected gold thioglucose. Injection of glucose into the lateral hypothalamus (LH) produced a small but significant and dose-dependent reduction in the firing rate of efferent sympathetic nerves to interscapular brown adipose tissue. Injection of insulin into the same region produced a very short-lived increase in efferent sympathetic firing rate. Bilateral lesions in the lateral hypothalamus produced by microinjection and gold thioglucose lowered body weight more than sham injections into the LH of control animals. There was an increase in basal sympathetic firing rate at 3, 9, and 24 h after LH lesions. There was also an increase in firing rate at 1 and 3 days, but by 7 days firing rate had returned to control levels. The data support the hypothesis that LH lesions enhance sympathetic activity but show only very limited modulation by glucose or insulin.

Effect of glucose and other hexoses on efferent discharges of brown adipose tissue nerves

1986 ◽  
Vol 251 (2) ◽  
pp. R240-R242 ◽  
Author(s):  
A. Niijima
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Sympathetic Nerves ◽  
Nerve Activity ◽  
Interscapular Brown Adipose Tissue ◽  
Brown Adipose ◽  
Diet Induced Thermogenesis ◽  
Effect Of Glucose

The activity of sympathetic nerves innervating interscapular brown adipose tissue of the rat was recorded. Intravenous administrations of glucose (100-300 mg/kg) enhanced the nerve activity. However, mannose, fructose, or galactose (300 mg/kg) showed no effect, suggesting the response is related to diet-induced thermogenesis in the brown adipose tissue.

scholarly journals Central efferent pathways mediating skin cooling-evoked sympathetic thermogenesis in brown adipose tissue

2007 ◽  
Vol 292 (1) ◽  
pp. R127-R136 ◽  
Author(s):  
Kazuhiro Nakamura ◽  
Shaun F. Morrison
Keyword(s):  
Heart Rate ◽  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Receptor Agonist ◽  
Excitatory Amino Acid ◽  
Defense Responses ◽  
Hypothalamic Nucleus ◽  
Brown Adipose ◽  
Skin Cooling ◽  
Efferent Pathways

Control of thermoregulatory effectors by the autonomic nervous system is a critical component of rapid cold-defense responses, which are triggered by thermal information from the skin. However, the central autonomic mechanism driving thermoregulatory effector responses to skin thermal signals remains to be determined. Here, we examined the involvement of several autonomic brain regions in sympathetic thermogenic responses in brown adipose tissue (BAT) to skin cooling in urethane-chloralose-anesthetized rats by monitoring thermogenic [BAT sympathetic nerve activity (SNA) and BAT temperature], metabolic (expired CO2), and cardiovascular (arterial pressure and heart rate) parameters. Acute skin cooling, which did not reduce either rectal (core) or brain temperature, evoked increases in BAT SNA, BAT temperature, expired CO2, and heart rate. Skin cooling-evoked thermogenic, metabolic, and heart rate responses were inhibited by bilateral microinjections of bicuculline (GABAA receptor antagonist) into the preoptic area (POA), by bilateral microinjections of muscimol (GABAA receptor agonist) into the dorsomedial hypothalamic nucleus (DMH), or by microinjection of muscimol, glycine, 8-OH-DPAT (5-HT1A receptor agonist), or kynurenate (nonselective antagonist for ionotropic excitatory amino acid receptors) into the rostral raphe pallidus nucleus (rRPa) but not by bilateral muscimol injections into the lateral/dorsolateral part or ventrolateral part of the caudal periaqueductal gray. These results implicate the POA, DMH, and rRPa in the central efferent pathways for thermogenic, metabolic, and cardiac responses to skin cooling, and suggest that these pathways can be modulated by serotonergic inputs to the medullary raphe.

Brown adipose tissue after ventromedial hypothalamic lesions in rats

1985 ◽  
Vol 248 (1) ◽  
pp. E20-E25 ◽  
Author(s):  
M. Saito ◽  
Y. Minokoshi ◽  
T. Shimazu
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Lipid Droplets ◽  
Temperature Response ◽  
Sympathetic Nerves ◽  
Acid Synthesis ◽  
Ventromedial Hypothalamus ◽  
Interscapular Brown Adipose Tissue ◽  
Brown Adipose ◽  
Obese Rats

The interscapular brown adipose tissue (IBAT) from obese rats with lesions of the ventromedial hypothalamus (VMH) was approximately 5 times heavier than those from controls. This hypertrophy of IBAT was associated with a marked enlargement of constituent adipocytes and their apparent transformation from multiloculated structure of lipid droplets into the uniloculated structure. The rate of fatty acid synthesis in IBAT of the obese rats was less than one-tenth of that in control rats and approximated the value in white adipose tissue (WAT) when they were starved for 24 h. When rats were fed, the synthetic rate was increased, but the lipogenic response of IBAT in the obese rats was much greater than that in controls, the extent of the response being comparable to that of WAT. The IBAT temperature rose rapidly on electrical stimulation of the sympathetic nerves to the tissue in control rats, whereas the temperature response was reduced markedly in the obese rats. It was suggested that thermogenesis in BAT was impaired in obese rats with VMH lesions by decreasing triglyceride turnover in BAT, probably due to dysfunction of the sympathetic nervous system and a consequent transformation of BAT into WAT.

scholarly journals Central melanocortin stimulation increases phosphorylated perilipin A and hormone-sensitive lipase in adipose tissues

2010 ◽  
Vol 299 (1) ◽  
pp. R140-R149 ◽  
Author(s):  
Y. B. Shrestha ◽  
C. H. Vaughan ◽  
B. J. Smith ◽  
C. K. Song ◽  
D. J. Baro ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Fatty Acid ◽  
Free Fatty Acid ◽  
Sympathetic Nerves ◽  
Hormone Sensitive Lipase ◽  
Interscapular Brown Adipose Tissue ◽  
Brown Adipose ◽  
Perilipin A ◽  
Hormone Sensitive

Norepinephrine (NE) released from the sympathetic nerves innervating white adipose tissue (WAT) is the principal initiator of lipolysis in mammals. Central WAT sympathetic outflow neurons express melanocortin 4-receptor (MC4-R) mRNA. Single central injection of melanotan II (MTII; MC3/4-R agonist) nonuniformly increases WAT NE turnover (NETO), increases interscapular brown adipose tissue (IBAT) NETO, and increases the circulating lipolytic products glycerol and free fatty acid. The WAT pads that contributed to this lipolysis were inferred from the increases in NETO. Because phosphorylation of perilipin A (p-perilipin A) and hormone-sensitive lipase are necessary for NE-triggered lipolysis, we tested whether MTII would increase these intracellular markers of lipolysis. Male Siberian hamsters received a single 3rd ventricular injection of MTII or saline. Trunk blood was collected at 0.5, 1.0, and 2.0 h postinjection from excised inguinal, retroperitoneal, and epididymal WAT (IWAT, RWAT, and EWAT, respectively) and IBAT pads. MTII increased circulating glycerol concentrations at 0.5 and 1.0 h, whereas free fatty acid concentrations were increased at 1.0 and 2.0 h. Western blot analysis showed that MTII specifically increased p-perilipin A and hormone-sensitive lipase only in fat pads that previously had MTII-induced increases in NETO. Phosphorylation increased in IWAT at all time points and IBAT at 0.5 h, but not RWAT or EWAT at any time point. These results show for the first time in rodents that p-perilipin A can serve as an in vivo, fat pad-specific indictor of lipolysis and extend our previous findings showing that central melanocortin stimulation increases WAT lipolysis.

Role of ventromedial hypothalamus on sympathetic efferents of brown adipose tissue

1984 ◽  
Vol 247 (4) ◽  
pp. R650-R654 ◽  
Author(s):  
A. Niijima ◽  
F. Rohner-Jeanrenaud ◽  
B. Jeanrenaud
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Spontaneous Activity ◽  
Sympathetic Innervation ◽  
Sympathetic Nerves ◽  
Ventromedial Hypothalamus ◽  
Functional Link ◽  
Interscapular Brown Adipose Tissue ◽  
Cold Stimulus ◽  
Brown Adipose

Previous studies have suggested the presence, in hypothalamic obesity, of an impairment of the energy-dissipating capacity of brown adipose tissue ascribed to a functional disconnection of the sympathetic innervation of this tissue. The following observations demonstrate, with electrophysiological techniques, the presence of a functional link between the ventromedial hypothalamic (VMH) area and the interscapular brown adipose tissue (IBAT) in the rat: the spontaneous activity of the efferent sympathetic nerves reaching the IBAT of normal rats was increased in response to an acute cold stimulus, whereas this increase failed to occur in nerves of VMH-lesioned rats studied 4–7 days after the lesions; and the spontaneous activity of the efferent sympathetic nerves of IBAT decreased rapidly (by greater than or equal to 80% within 30 min) after acute lesions of the VMH area. It is suggested that the VMH area plays a role in increasing the activity of the efferent sympathetic nerves of IBAT during an acute cold stimulus and that alone or in relationship with other, as yet undetermined, central nervous system sites, it has a tonic stimulatory effect on the final common pathways that innervate the IBAT via the efferent sympathetic nerves.

Effects of chronic lard feeding on sympathetic nervous system activity in the rat

1994 ◽  
Vol 267 (5) ◽  
pp. R1320-R1328 ◽  
Author(s):  
J. B. Young ◽  
P. A. Daly ◽  
K. Uemura ◽  
F. Chaouloff
Keyword(s):  
Nervous System ◽  
Sympathetic Nervous System ◽  
Sympathetic Nerves ◽  
Plasma Norepinephrine ◽  
Interscapular Brown Adipose Tissue ◽  
Brown Adipose ◽  
Chronic Ingestion ◽  
Sympathetic Nervous ◽  
Specific Stimulation ◽  
Kidney Liver

The level of sympathetic nervous system (SNS) activity in obesity is controversial, with reports claiming either increased or decreased SNS activity. The following studies examined SNS activity in a dietary form of obesity, ingestion of a lard-enriched diet for 4 wk. Plasma norepinephrine (NE) levels were 61% higher in rats fed the lard-enriched diet than in chow-fed controls at 20 degrees C (200 +/- 24 pg/ml vs. 124 +/- 6, P < 0.005) and remained elevated after 1 h of cold exposure (4 degrees C). [3H]NE turnover was markedly increased in heart, but not in interscapular brown adipose tissue (IBAT), kidney, liver, skeletal muscle, or spleen of rats fed the high-fat diet. By contrast, ingestion of a diet similarly enriched with sucrose raised rates of [3H]NE turnover in IBAT as well as in heart. Thus chronic ingestion of a lard-enriched diet induces region-specific stimulation of SNS activity that is greater in heart than in IBAT. Whereas the absence of an SNS response to lard in IBAT may contribute to weight gain in these animals, activation of cardiac sympathetic nerves may promote development of hypertension in this model of obesity.

Neostigmine in the hippocampus increases thermogenesis and T4-to-T3 conversion

1996 ◽  
Vol 270 (6) ◽  
pp. R1215-R1219 ◽  
Author(s):  
M. Monda ◽  
A. Papa ◽  
G. Brizzi ◽  
B. DeLuca
Keyword(s):  
Firing Rate ◽  
Blood Level ◽  
Sympathetic Nerves ◽  
O2 Consumption ◽  
Saline Injection ◽  
Sprague Dawley ◽  
Interscapular Brown Adipose Tissue ◽  
Sprague Dawley Rats ◽  
Brown Adipose ◽  
Baseline Values

The firing rate of the nerves innervating interscapular brown adipose tissue (IBAT), IBAT and colonic temperatures (TIBAT and TC), and O2 consumption were monitored in urethan-anesthetized male Sprague-Dawley rats. These variables were measured for 40 min before (baseline values) and 40 min after a neostigmine (5 x 10(-7) mol) or saline injection in the hippocampus. The blood level of 3,5,3'-triiodothyronine and L-thyroxine (T3 and T4) and the 5'-deiodinating activity of IBAT, liver, and kidneys were determined in other rats with neostigmine or saline injection. The results showed that neostigmine injection increased firing rate, TIBAT, TC, O2 consumption, blood level of T3, and 5'-deiodinating activity of IBAT. No change was found in the T4 level and in 5'-deiodinating activity of the liver and kidneys. These findings suggest that neostigmine injection in the hippocampus increases heat production by stimulating sympathetic nerves to IBAT and by elevating the blood level of T3.

scholarly journals Altered frequency responses of sympathetic nerve discharge bursts after IL-1β and mild hypothermia

2002 ◽  
Vol 93 (1) ◽  
pp. 280-288 ◽  
Author(s):  
M. J. Kenney ◽  
F. Blecha ◽  
R. J. Fels ◽  
D. A. Morgan
Keyword(s):  
Sympathetic Nerve ◽  
Neural Circuits ◽  
Mild Hypothermia ◽  
Sympathetic Nerves ◽  
Interscapular Brown Adipose Tissue ◽  
Frequency Responses ◽  
Brown Adipose ◽  
Complex Relationships ◽  
Colonic Temperature ◽  
Nerve Discharge

Although interleukin-1β (IL-1β) administration produces nonuniform changes in the level of sympathetic nerve discharge (SND), the effect of IL-1β on the frequency-domain relationships between discharges in different sympathetic nerves is not known. Autospectral and coherence analyses were used to determine the effect of IL-1β and mild hypothermia (60 min after IL-1β, colonic temperature from 38°C to 36°C) on the relationships between renal-interscapular brown adipose tissue (IBAT) and splenic-lumbar sympathetic nerve discharges in chloralose-anesthetized rats. The following observations were made. 1) IL-1β did not alter renal-IBAT coherence values in the 0- to 2-Hz frequency band or at the cardiac frequency (CF). 2) Peak coherence values relating splenic-lumbar discharges at the CF were significantly increased after IL-1β and during hypothermia. 3) Hypothermia after IL-1β significantly reduced the coupling (0–2 Hz and CF) between renal-IBAT but not splenic-lumbar SND bursts. 4) Combining IL-1β and mild hypothermia had a greater effect on renal-IBAT SND coherence values than did mild hypothermia alone. These data demonstrate functional plasticity in sympathetic neural circuits and suggest complex relationships between immune products and SND regulation.

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