Articles de blog de mohammed benyamina
Tout le monde (grand public)
The effect of cholinergic agonists on glucocorticoid
and mineralocorticoid production by frog interrenal
(adrenal) tissue was studied in vitro by means of
continuous perifusion. Acetylcholine, at doses ranging
from 1 to 100 \g=m\mol/l,stimulated both corticosterone
and aldosterone output in a dose-dependent manner,
with a half-maximal effective dose of 2\m=.\5 \g=m\mol/l.
Corticosteroid production was also stimulated by
muscarine (10 \g=m\mol/l).In contrast, neither nicotine
nor nicotine bitartrate (1\p=n-\100 \g=m\mol/l)enhanced corticosteroid
biosynthesis. The kinetics of the response of
adrenal cells to acetylcholine and muscarine were
similar to those observed during angiotensin II stimulation.
In particular, a significant reduction (20\p=n-\40%)
in the spontaneous level of corticosteroid production
was recorded after the initial infusion of muscarinic
agents, but no further decrease in the basal level
occurred after a second cholinergic administration.
The effect of acetylcholine was blocked by the
muscarinic receptor antagonist atropine (10 \g=m\mol/l).
These results indicate that acetylcholine can stimulate
frog adrenocortical cells through muscarinic receptors.
Repeated 20-min pulses of acetylcholine (50 \g=m\mol/l)or
muscarine (10 \g=m\mol/l),given at one pulse per 130 min,
resulted in a marked reduction in the secretory response
to the second pulse. No reduction in the stimulatory
effect of acetylcholine or muscarine was observed when
a 6\m=.\5-h interval separated two 20-min infusions of the
secretagogue. In contrast with these findings, iterative
pulses of the muscarinic agonist pilocarpine (in the
range 1\p=n-\100 \g=m\mol/l)did not cause any desensitization.
These data show that the neurotransmitter acetylcholine
can modulate frog adrenocortical function
and suggest that, in addition to more conventional
regulators, i.e. ACTH and angiotensin II, the
cholinergic endings of the splanchnic nerve might
participate in the regulation ofcorticosteroid secretion,
at least under so
[ Modifié: dimanche 24 janvier 2021, 21:11 ]