[Effect of muscimol (GABA-agonist) on thalamo-hypothalamic regulation by corticotropic efferents (thalamic model)].
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 late rebounding components. Intravenous injection of muscimol (0.5 ml . kg-1) produces only slight and short duration (45 min) disturbances (piloerection; panting; corticosteronemia). Stress application, 1 hr after muscimol administration, elicits only the first peak of corticosterone with magnitude and delay similar to that in control. However, the late rebounding component is no more visible. Thus, GABA-ergic stimulation leads to a situation similar to that seen after section of neural connections between thalamic nuclei and infundibular complex. The hypothalamic-adrenocorticotropic reactivity itself is not affected whereas the function of the regulating thalamo-hypothalamic loop is markedly impaired.
D000818:Animals; D010856:Columbidae; D003345:Corticosterone / Q000378:metabolism*; D004525:Efferent Pathways / Q000187:drug effects / Q000502:physiology*; D007031:Hypothalamus / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D009118:Muscimol / Q000494:pharmacology*; D013312:Stress, Physiological / Q000503:physiopathology; D013788:Thalamus / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology
D009118:Muscimol; D003345:Corticosterone
Influence du muscimol (GABA-agoniste) sur une boucle de régulation thalamo-hypothalamique à efférence corticotrope (modèle thalamique).