Blockade of ghrelin receptor signaling enhances conditioned passive avoidance and context-associated cFos activation in fasted male rats

Interoceptive feedback to the brain regarding the body ’s physiological state plays an important role in guiding motivated behaviors. For example, a state of negative energy balance tends to increase exploratory/food-seeking behaviors while reducing avoidance behaviors. We recently reported that overnight food deprivation reduces conditioned passive a voidance behavior in male (but not female) rats. Since fasting increases circulating levels of ghrelin, we hypothesized that ghrelin signaling contributes to the ability of fasting to reduce conditioned avoidance. To test this, ad libitum-fed male rats were trained in a passive avoidance procedure u sing mild footshock. Later, following overnight food deprivation, the same rats were pretreated with ghrelin receptor antagonist (GRA) or saline vehicle 30 min before avoidance testing. GRA restored passive avoidance in fasted rats as measured both by latency to enter and time spent in the shock-pai red context. In addition, compared to vehicle-injected fasted rats, fasted rats that received GRA before re-exposure to the shock-paired context displayed more cFos activation of prolactin-releasing peptide (PrRP)-positive noradrenergic (NA) neurons in the caudal nucleus of the solitary tract, accom panied by more cFos activation in downstream target sites of PrRP neurons (i.e., bed nucleus of the stria terminalis and paraventricular nucleus of the hypothalamus). These results support the view that ghrelin signaling contributes to the i...
Source: Neuroendocrinology - Category: Endocrinology Source Type: research