Central and peripheral actions of alpha-MSH in the thermoregulation of rats.

The effect of alpha-MSH on thermoregulation in rats at room temperature was examined. alpha-MSH (1 microgram ICV or 30 micrograms IP) alone did not alter temperature. However, this peptide was a potent antipyretic when administered centrally or peripherally in rats treated with pyrogen derived from Salmonella typhi.     

Central and peripheral actions of α-MSH in the thermoregulation of rats

The effect of α-MSH on thermoregulation in rats at room temperature was examined. α-MSH (1 μg ICV or 30 μg IP) alone did not alter temperature. However, this peptide was a potent antipyretic when administered centrally or peripherally in rats treated with pyrogen derived from Salmonella typhi.     

Central administration of peptides alters thermoregulation in the rabbit

Sixteen peptides were injected intracerebroventricularly to test their effects on rectal temperature of rabbits in a thermoneutral environment. In initial tests 5 μg α-MSH, ACTH(1–24), oxytocin, vasopressin and glucagon altered body temperature while ACTH(1–10), cholecystokinin, contraceptive tetrapeptide, gastrin, insulin, interferon, leupeptin, LHRH, panhibin (somatostatin), and proctolin did not. Bombesin also altered body temperature but in no consistent direction. In further tests on the effective peptides 1.25–5.0 μg α-MSH and ACTH(1–24) produced dose-related decreases in rectal temperature as great as 1.0°C. The same doses of oxytocin and glucagon produced small, prolonged hyperthermias which did not exceed 0.4°C. Vasopressin caused rapid development of small increases in rectal temperature; temperature returned to normal in 2–3 hr. The results suggest that five of the peptides tested may have roles in central mediation of normal body temperature, hypothermia, hyperthermia and fever.     

A dynamic inline sample thermoregulation unit for flow cytometry

BACKGROUND: Flow cytometry is a valuable tool for the study of cellular and molecular interactions. We sought to develop instrumentation that would allow accurate and precise inline dynamic temperature control of flow cytometry samples in order to expand the analytical capabilities of flow cytometry. METHODS: Using a temperature controller, DC power supply, and a Peltier module, we designed a temperature control circuit that regulates the temperature of a heat transfer block. The heat transfer block surrounds the sample line to efficiently heat and cool the sample. We attached DNA oligomers to microspheres and observed the denaturation of fluorescently labeled complementary oligomers to verify that the sample was achieving the desired temperature. RESULTS: The inline thermoregulation unit can ramp between 30 and 95 degrees C (>2 degrees C per second) within 30 s repeatedly. The accuracy of the instrument was verified by comparing the observed melting temperatures of the oligomer sets to the predicted values. These values varied within 6% of the predicted and were reproducible over a variety of conditions. CONCLUSIONS: The apparatus we constructed accurately and dynamically controls the sample temperature of inline samples. Flow cytometers equipped with our inline thermoregulation unit will be able to conveniently use temperature as a robust experimental parameter.     

Central angiotensin AT1-receptor blockade affects thermoregulation and running performance in rats

The effect of central angiotensin AT1-receptor blockade on thermoregulation in rats during exercise on a treadmill (18 m/min, 5% inclination) was investigated. Core (Tb) and skin tail temperatures were measured in rats while they were exercising until fatigue after injection of 2 microl of losartan (Los; 20 nmol, n = 4; 30 nmol, n = 4; 60 nmol, n = 7), an angiotensin II AT1-receptor antagonist, or 2 microl of 0.15 mol/l NaCl (Sal; n = 15) into the right lateral cerebral ventricle. Body heat rate (BHR), heat storage rate, threshold Tb for tail vasodilation (TTbV), time to fatigue, and workload were calculated. During exercise, the BHR and heat storage rate of Los-treated animals were, respectively, 40 and 53% higher (P < 0.01) than in Sal-treated animals. Additionally, rats injected with Los showed an increased TTbV (38.59 +/- 0.19 degrees C for Los vs. 38.12 +/- 0.1 degrees C for Sal, P < 0.02), a higher Tb at fatigue point (39.07 +/- 0.14 degrees C Los vs. 38.66 +/- 0.07 degrees C Sal, P < 0.01), and a reduced running performance (27.29 +/- 4.48 min Los vs. 52.47 +/- 6.67 min Sal, P < 0.01), which was closely related to the increased BHR. Our data suggest that AT1-receptor blockade attenuates heat dissipation during exercise due to the higher TTbV, leading to a faster exercise-induced increase in Tb, thus decreasing running performance.     

Readjustment of peripheral factors during the unsteady-state phase of dynamic muscular exercise

The behaviour of the ratio: oxygen extraction (total peripheral resistance (DAV/TPR) in a group of untrained healthy young male students has been bloodless investigated during the unsteady-state phase of the dynamic muscular exercise (2.5 watt/Kg). The results obtained have shown that the kinetics of the ratio, from a resting value of 3.40 ml O2 . min-1 . mmHg-1 to a figure of 17.62 (steady-state) doesn't follow a step function. During the first 30 seconds the percentual increase of the ratio falls to 0.45, becomes 1.5 thirty seconds later and there this exponentially drops down to a value of 1. The observed behaviour agrees with experimental findings of other authors.     

Central and peripheral noradrenergic tone in primary hypertension

The contents of norepinephrine (NE), epinephrine (E), dopamine (DA), normetanephrine (NMN), and 4-hydroxy-3-methoxyphenylethylene glycol (MHPG) were measured in the plasma and cerebrospinal fluid (CSF) of 66 patients with primary hypertension and 24 patients with normal blood pressure and minor neurological disorders. Plasma and CSF NE and NMN concentrations were raised in the hypertensive patients. The plasma and CSF NE levels and arterial blood pressure of a small subset of hypertensive patients were normalized after clonidine therapy. In hypertensive patients the content of DA was lower and the ratio of NE/DA was greater; CSF and plasma NE contents were related to the level of arterial blood pressure; and the content of MHPG in CSF was linked strongly with NE content in plasma and CSF and to the level of arterial blood pressure. Thus both central sympathetic nerve tone and peripheral sympathetic nerve tone were enhanced in young patients with uncomplicated hypertension. The elevated levels of neurohormones and their metabolites in some patients with primary hypertension may be related to increased synthesis and release of neural NE and may be pathogenic in the blood pressure elevation.     

Central and peripheral mechanisms of difficult breathing in man

The review is dedicated of phenomenology of the difficult breathing and analysis of the peripheral and central mechanisms of it. Analysis based on model investigations with resistive loads in awake or sleeping healthy humans, including results of experiments in the anesthetized animals. The recent data having principle importance in estimation of the central mechanisms of the control breathing are included too in the review. It concerned to the contemporary visualization of central neuronal activity on the awake person during dyspnoea. It became possible due to application of the unique precision equipment--functional magnetic--resonance and positron--emission tomography.     

Central and peripheral proglumide administration and cholecystokinin-induced satiety

Peripheral (50 mg/ml) or central (50 micrograms/microliter) injections of proglumide were made into Sprague-Dawley rats which displayed satiety-like responses after the peripheral (100 micrograms/kg) or central (50 ng in 1 microliter) administration of cholecystokinin (CCK). The satiety produced by CCK injection into the lateral hypothalamus, area postraema and ventromedial hypothalamus was significantly reversed by proglumide injections into these areas during a 4 h food intake test. Peripheral injection of proglumide after central or peripheral CCK injection did not modify this type of CCK-induced satiety. Central proglumide injection produced a reliable decrease in water intake and this is compatible with previous findings which describe the stimulation of water intake after central gastrin administration. These results suggest that various central and peripheral mechanisms which are involved in the regulation of appetite may function independently as a 'failsafe' system.     

Central and peripheral cardiovascular actions of apelin in conscious rats

APJ was cloned as an orphan G protein-coupled receptor and shares a close identity with angiotensin II type 1 receptor (AT1R). Apelin is a peptide that has recently been identified as an endogenous ligand of the APJ. Apelin and APJ mRNA are expressed in peripheral tissue and the central nervous system. However, little is known about the effects of apelin in cardiovascular regulation. To examine the central and peripheral role of apelin, we injected the active fragment of apelin [(Pyr1)apelin-13] intracerebroventricularly (ICV, 5 and 20 nmol, n=6) or intravenously (IV, 20 and 50 nmol, n=4 or 5) in conscious rats. ICV injection of (Pyr1)apelin-13 dose-dependently increased mean arterial pressure (MAP) and heart rate (HR) (19+/-3 mm Hg and 162+/-26 bpm at 20 nmol). Pretreatment with ICV injection of the AT1R antagonist (CV-11974, 20 nmol) did not alter the apelin-induced increase in MAP and HR. IV injection of (Pyr1)apelin-13 also dose-dependently increased MAP and HR (13+/-2 mm Hg and 103+/-18 bpm at 50 nmol); however, the peripheral effects of apelin were relatively weak compared to its central effects. Expression of c-fos in the paraventricular nucleus (PVN) of hypothalamus was increased in the rat that received ICV injection of (Pyr1)apelin-13 but not in the rat that received IV injection of (Pyr1)apelin-13. These results suggest that apelin plays a role in both central and peripheral cardiovascular regulation in conscious rats, and that the cardiovascular effects of apelin are not mediated by the AT1R.     

Central and peripheral des-acyl ghrelin regulates body temperature in rats

In the present study using rats, we demonstrated that central and peripheral administration of des-acyl ghrelin induced a decrease in the surface temperature of the back, and an increase in the surface temperature of the tail, although the effect of peripheral administration was less marked than that of central administration. Furthermore, these effects of centrally administered des-acyl ghrelin could not be prevented by pretreatment with [D-Lys3]-GHRP-6 GH secretagogue receptor 1a (GHS-R1a) antagonists. Moreover, these actions of des-acyl ghrelin on body temperature were inhibited by the parasympathetic nerve blocker methylscopolamine but not by the sympathetic nerve blocker timolol. Using immunohistochemistry, we confirmed that des-acyl ghrelin induced an increase of cFos expression in the median preoptic nucleus (MnPO). Additionally, we found that des-acyl ghrelin dilated the aorta and tail artery in vitro. These results indicate that centrally administered des-acyl ghrelin regulates body temperature via the parasympathetic nervous system by activating neurons in the MnPO through interactions with a specific receptor distinct from the GHS-R1a, and that peripherally administered des-acyl ghrelin acts on the central nervous system by passing through the blood–brain barrier, whereas it exerts a direct action on the peripheral vascular system.     

Specific dynamic action of a high-protein diet and its significance for thermoregulation in the golden hamster.

As a result of the specific dynamic action of a high-protein diet the resting metabolism of golden hamsters within the zone of thermoneutrality is increased on a average by 40%. The specific dynamic action diminishes markedly, with declining environmental temperature. It is concluded from this results that part of the heat produced by the specific dynamic action of a high-protein diet leads to a rise in the lower critical temperature in the zone of thermoneutrality by 2 degrees C.