Gastric saline infusion reduces ultrasonic vocalizations and brown fat activity in suckling rat pups

Abstract

Under standard conditions involving isolation and cooling, it has been documented that intraoral infusion of milk and injection of the intestinal peptide cholecystokinin (CCK) result in an attenuation in ultrasonic vocalizations (USV) emitted by infant rat pups. One of the most effective stimuli in inhibiting ingestion in suckling rat pups is gastric distension, but the effect of gastric distension on USV production has not been reported. In this experiment, we subjected infant rats to intragastric infusion of isotonic saline (2% body weight) to produce a natural level of gastric distension and hydration. We found that this stimulus resulted in a powerful reduction in USV emissions in isolated 10-day-old rats. In a subsequent experiment, we found that gastric saline infusion also diminished brown adipose tissue (BAT) thermogenesis. There were different time courses of the gastric saline infusion effects on BAT thermogenesis and on USV emissions, however, suggesting that these processes may be independently regulated. We hypothesize that this stimulus induces a transient activation of the parasympathetic nervous system, which overrides the sympathetic control of BAT and USV production.

A full belly and colostrum: Two major determinants of filial love

“…Nonetheless, if the vocal activity between lambs receiving 10% BWT of colostrum or saline differs, there still is the possibility that the postprandial effects of the two fluids are quite alike, as lambs infused with saline were globally less vocal than sham lambs. In rat pups, gastric saline infusion, mimicking a natural level of gastric distension and hydration, reduces ultrasonic vocalizations (Nelson & Alberts, 2002) and increases paradoxical sleep (Lorenz et al, 1998). Beyond a threshold, therefore, the infusion of saline also may facilitate the development of mother preference in lambs through a ''comforted state'' induced by noncaloric, nonnutritional factors.…”

Ultrasonic Vocalizations Emission across Development in Rats: Coordination with Respiration and Impact on Brain Neural Dynamics

“…Moreover, other factors affect the number of USV emitted. For example, a satiated state, the presence of the mother or littermates on the floor of the recording cage, or the presence of a threat all decrease USV production, despite having diverse consequences on the pup’s anxiety level [ 54 , 56 , 65 , 66 , 67 ]. By contrast, reisolating a pup after a short reunion with its mother potentiates the number of USV emitted, even though the mother inhibits the HPA axis of the pup (i.e., its stress response) [ 67 , 68 , 69 , 70 ].…”

Postnatal Development of Central Feeding Circuits

“…CCK also has been reported to elicit and prolong rest behavior and sleep in adult rats (Mansbach & Lorenz, 1983). These effects of exogenous CCK are similar to those produced in pups by intragastric saline infusion, which reduces ultrasonic vocalizations in maternally deprived neonates (Nelson & Alberts, 2002). The calming effects of milk or saline in rat pups could be due to gastric distension or to rehydration.…”