Load-sensitive rat gastric vagal afferents encode volume but not gastric nutrients.
To assess nutrient sensitivity in a population of gastric load-sensitive vagal afferents, their neurophysiological activity was examined in anesthetized rats with inflated pyloric cuffs after gastric infusion of a range of volumes of nutrient and equiosmotic saline solutions. Responses to physiological saline loads (1, 2, 4, and 8 ml) were compared with responses elicited by the same volume range of carbohydrate (12.5% glucose), protein (12.5% peptone), and equiosmotic hypertonic (750 mosM) saline. The threshold load volume of physiological saline required to increase gastric vagal afferent activity was 1 ml. Thereafter, there was a dose-dependent relationship between increasing gastric volume and firing rate and between gastric volume and pressure. The dose-response relationships elicited by glucose, peptone, and equiosmotic hypertonic saline loads did not differ from those elicited by physiological saline loads. These data identify a population of gastric load-sensitive vagal afferents unresponsive to the chemical composition of gastric contents and are consistent with a role for vagal gastric volume signals but not gastric nutrient content in the negative feedback control of ingestion.
Mathis
C
C
Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2196, USA.
Moran
T H
TH
Schwartz
G J
GJ
D000344:Afferent Pathways / Q000502:physiology*; D000818:Animals; D004435:Eating; D004594:Electrophysiology; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D009994:Osmolar Concentration; D010461:Peptones / Q000008:administration & dosage / Q000494:pharmacology; D011312:Pressure; D051381:Rats; D017207:Rats, Sprague-Dawley; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D013270:Stomach / Q000294:innervation* / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*
D010461:Peptones; D012462:Saline Solution, Hypertonic; D012965:Sodium Chloride; D005947:Glucose