F Ramade

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Hemispherectomized pigeons were exposed daily to electrical footshocks delivered for 15 sec, at the same hour, for 8 weeks. Serial blood samples were obtained through a chronic vascular catheter. The adrenocortical response to chronic intermittent stress was measured kinetically at one week intervals. The initial response including several successive peaks(More)
Muscimol was chronically administrated to the third ventricle of thalamic pigeons by means of osmotic minipumps at the rate of 0.25 microgram X h-1 for 28 days. No abnormal behavioural sign was noted. The animals were subjected daily to chronic intermittent stress for the same 28-day period. Basal and stress-induced adrenocortical activities were evaluated(More)
The functioning of the hypothalamic pituitary-adrenocortical system was tested in young pigeons before and after hatching, by radiocompetitive assay of plasma corticosterone (B) at rest and under stress. 1 degree B was expressed in ng/ml. Resting adult values (8-10) could not be observed before the birds were 6 week-old. B levels were very low 36 h before(More)
The role of diencephalic cholinergic neurotransmission in regulating hypothalamic-pituitary-adrenocortical (HPA) axis was investigated by means of administration of hemicholinium-3 (HC-3), a blocker of acetylcholine synthesis, in the third ventricle of hemispherectomized pigeons. Except for an early increase in ACTH and corticosterone levels following(More)
Plasma levels of both adrenocorticotropic hormone (ACTH) and corticosterone (B) were determined in embryos (day 15 of incubation), chicks (day 3 after hatch) and young chickens (8 weeks). Experimental animals were bursectomized at 80 hr of incubation, i.e., before any anlage of the bursa of Fabricius could develop. Bursectomized (BFX) animals were compared(More)
The thalamic pigeon was taken as a model to investigate mechanisms of adaptation to chronic intermittent stress. Muscimol was infused into the 3rd ventricle at the rate of 0.25 microgram.hr-1 by means of an osmotic minipump. In controls, pumps were filled in with saline. Animals were placed under constant light regimen and electrical foot shocks were(More)
Muscimol was injected (0.5 mg kg-1) intravenously to either intact or thalamic-lesioned animals through a chronic catheter. Plasma samples were obtained at 7-min intervals and exhibited a moderate and transient increase in corticosterone levels in both groups, together with some symptoms of light discomfort (e.g., ptiloerection or panting). All these signs(More)
It can be assumed from previous data that the stress-induced polyphasic adrenocortical response involves two phenomenons. First, direct hypothalamic afferents stimulate the adrenocorticotropic axis resulting in a rapid increase in plasma corticosterone levels up to a maximum of about 40 ng . ml-1 at 15 min. Then, a thalamic-hypothalamic loop generates the(More)
Exposure of control quail to low ambient temperature (4 degrees) for a short duration (15 min) led to a rapid increase in plasma thyroxine (T4) levels. A peak appeared 40 min after the cold began and was followed by a progressive and slow decline. T4 levels were elevated in birds maintained for up to 3 hr at 4 degrees. Restraint stress could be accompanied(More)
Chronic vascular catheterization allowed to obtain serial blood samples before and after stress application to thalamic pigeons. Daily repetition of the same stress, at the same hour, for 5 weeks led to drastic changes in the stress-induced adrenocortical reaction. The rebounding, long-lasting rise in plasma corticosterone occurring after initial(More)