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R Hissa

Publications and source records attributed to R Hissa.

At least 55 records · Page 3Linked to original sources
PubMed1978

The influence of high ambient temperature on thermoregulatory response to intrahypothalamic injections of noradrenaline and serotonin in the pigeon.

1. Pigeons with chronically implanted injection cannula in the hypothalamus were injected with noradrenaline (NA, 10 micrograms/microliter) and 5-hydroxytryptamine (5-HT, 10 micrograms/microliter) at the ambient temperature (Ta) of 38 degrees or 42 degrees C. 2. Initial tests at cold (6 degrees C) indicated that birds responded hypothermically to NA and in most instances also to 5-HT. 3. Intrahypothalamic injection of NA (10 micrograms/microliter) had no appreciable effect on oxygen consumption (VO2), body temperature (Tb), foot temperature (Tf), or heart and respiratory rates at Ta 38 degrees C. The increase of VO2, Tb and Tf noted after similar injection at 42 degrees C was in all probability due to observed excitement and bursts of struggling rather than effects on thermoregulatory mechanisms. 4. 5-HT (10 micrograms/microliter) injected at Ta 38 degrees C depressed respiratory frequency from panting (600 breaths.min-1) to normal rate (ca. 50.min-1) within 2--4 min. The absence of panting lasted about 10 min, but only a slight increase of VO2, Tb and Tf followed. At Ta 42 degrees C, no notable changes of VO2, Tb and Tf were recorded after 5-HT injection. 5. It is concluded that 5-HT has an inhibitory action on neuronal pathway controlling panting activity in the pigeon, but NA seems to be ineffective.

Animals↗
PubMed1978

Differential impairment of thermogenesis in the pigeon after chemical sympathectomy.

A dose-controlled chemical sympathectomy with 6-hydroxydopamine (6-OHDA) did not disrupt thermostasis in the pigeon at +38 degrees C. At +6 degrees C, thermogenesis was impaired, but the lower body temperature and oxygen consumption were stable and vasoconstriction was normal. The stability may partly be explained by a massive release of adrenaline from the adrenals (50% in 20 min). Despite a deficit in heat production both after sympathectomy and after acute 6-OHDA, no change in muscle electrical activity was observed. Plasma free fatty acid (FFA) concentration was significantly elevated after sympathectomy, but no changes occurred in blood glucose or plasma lactate levels. The results indicate a major compensatory role for the adrenals in avian thermogenesis. They also suggest a sympathetically mediated auxiliary thermogenic mechanism independent of muscle electrical activity and coupled to FFA metabolism.

Adrenal Glands↗
PubMed1977

Effect of intrahypothalamic phentolamine on hypothermia produced by peripheral noradrenaline in the pigeon.

1 The effect of intrahypothalamic phentolamine (1 and 1 microliter of a 10 microgram/microliter solution) on hypothermia induced by intramuscular injection of noradrenaline (NA, 2 mg/kg) at different times (2, 10, 20 min) after phentolamine was investigated in pigeons. 2 Administration of phentolamine shortly before NA was shown to attenuate hypothermic responses to NA. 3 It is suggested that the attenuation is due to blockade of central hypothermic effects of intramuscular NA. 4 The mapping of injection sites in the brains was carried out.

Animals↗
PubMed1977

Effect of glucagon on thermogenesis in the pigeon.

The effects of glucagon injection on temperature regulation and some metabolic parameters were studied in the pigeon. Glucagon (100 microng/kg) always inhibited shivering and caused a fall in the oxygen consumption and body temperature of the unanesthetized pigeon at + 6 degrees C. At + 34 degrees C, the same dose of glucagon had no effect on these parameters. At 22 degrees C, glucagon produced an elevation in plasma free fatty acid (FFA) and blood glucose levels. The rise in FFA at 22 degrees C coincided with the suppression of shivering at 6 degrees C. The glucagon-mediated rise in plasma FFA, but not glucose level, was potentiated by cold ambient temperature. Adrenergic blocking agents given prior to glucagon did not abolish its effects. Phentolamine even prolonged the absence and accelerated the suppression of shivering. A dissociation in the mechanisms by which catecholamines and glucagon suppress shivering is suggested. Although mobilizing energy reserves, glucagon does not seem to be calorigenic in the pigeon at this dose. The interpretation of the changes in plasma FFA levels is discussed in relation to fuel consumption during shivering.

Animals↗
PubMed1976

Effect of adrenergic blocing agents on peripheral noradrenaline induced thermoregulatory responses in the pigeon at heat.

1. The hyperthermic effect of intramuscular NA at 32 degrees C was abolished by propranolol but not by phentolamine preinjection. 2. The lack of hyperthermic response was at least partly due to the blocking effect of propranolol on beta-receptor mediated in heart rate. 3. After NA the respiratory rate was gradually increased in birds preinjected either with propranolol or with phentolamine.

Animals↗
PubMed1974

The influence of centrally applied noradrenaline on shivering and body temperature in the pigeon.

1. Noradrenaline (NA) was injected in a volume of 1.0 mul. through chronically implanted cannula into the hypothalamus of the unanaesthetized pigeon.2. In doses of 1-15 mug NA caused complete inhibition of shivering of dose-dependent duration. Histological mapping of the brain showed that NA was exerting its inhibitor action in the region above the optic chiasma bordering on the posterior hypothalamus and the anterior preoptic nucleus.3. At low ambient temperature, the NA induced inhibition of the cold tremor caused a fall of core temperature which lasted as long as shivering was inhibited. Shivering induced by local cooling of the spinal cord, and by the combined cooling of the skin and the spinal cord, was likewise inhibited by the cerebral application of NA. There was no evidence of an adjustment of the temperature set-point by NA.4. A rapid rise in skin temperature of the unfeathered feet, whenever NA was injected indicated a reduction in peripheral vasomotor tone.

Animals↗