Atrial stretch delays gastric emptying of liquids in awake rats.
OBJECTIVE
We previously reported that mechanical atrial stretch (AS) by balloon distention increased gastric tonus in anesthetized rats. The present study evaluated the effect of AS on the gastric emptying of a liquid test meal in awake rats and its underlying neural mechanisms.


METHODS
Anesthetized male rats received a balloon catheter into the right atrium and a gastrostomy cannula. The next day, mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), and cardiac output (CO) were continuously monitored. After the first 20min of monitoring (basal interval), the balloon was either distended or not (control) with 30, 50, or 70μl saline for 5min. Fifteen minutes later, the rats received the test meal (glucose solution with phenol red), and fractional gastric dye retention was determined 10, 20, or 30min later.


RESULTS
Heart rate and CVP values were transiently increased by 50 or 70μl AS but not 30μl AS, whereas gastric emptying was slower after 30, 50, or 70μl AS than after sham distention. Subdiaphragmatic vagotomy or splanchnicotomy+celiac ganglionectomy and capsaicin, ondansetron, hexamethonium, L-NAME, and glibenclamide treatment prevented the AS-induced delay in gastric emptying, whereas atropine and guanethidine treatment failed to prevent it.


CONCLUSIONS
Atrial stretch inhibited the gastric emptying of liquid via non-adrenergic and non-cholinergic pathways that activate nitric oxide-K(+)ATP channels.
Department of Physiology and Pharmacology, School of Medicine, Federal University of Ceará, Brazil.
R C
RC
Palheta
M T B
MT
Silva
H L G
HL
Barbosa
A D N
AD
Pinheiro
K V V
KV
Cardoso
J R V
JR
Graça
P J C
PJ
Magalhães
R B
RB
Oliveira
A A
AA
Santos
D000704:Analysis of Variance; D000818:Animals; D016280:Atrial Function, Right / Q000502:physiology*; D001285:Atropine / Q000494:pharmacology; D021721:Balloon Occlusion / Q000379:methods; D001794:Blood Pressure; D002211:Capsaicin / Q000494:pharmacology; D006328:Cardiac Catheterization / Q000379:methods; D002404:Catheterization / Q000379:methods; D005746:Gastric Emptying / Q000187:drug effects / Q000502:physiology*; D005772:Gastrointestinal Transit / Q000502:physiology*; D005774:Gastrostomy / Q000379:methods; D005905:Glyburide / Q000494:pharmacology; D006145:Guanethidine / Q000494:pharmacology; D006325:Heart Atria / Q000601:surgery*; D006339:Heart Rate; D018738:Hexamethonium / Q000494:pharmacology; D020896:Hypovolemia / Q000503:physiopathology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000097:blood; D017294:Ondansetron / Q000494:pharmacology; D051381:Rats
D009569:Nitric Oxide; D018738:Hexamethonium; D017294:Ondansetron; D001285:Atropine; D002211:Capsaicin; D005905:Glyburide; D019331:NG-Nitroarginine Methyl Ester; D006145:Guanethidine