Intraamygdaloid microinjection of acylated-ghrelin influences passive avoidance learning

Behav Brain Res. 2009 Sep 14;202(2):308-11. doi: 10.1016/j.bbr.2009.03.031. Epub 2009 Apr 1.

Abstract

The brain-gut peptide acylated-ghrelin (A-Ghr) is a potent growth hormone (GH) secretagogue substance. A-Ghr is also known to influence on memory and learning processes. Its effect is mediated partly via GH secretagogue receptor (GHS-R) type 1a. The amygdaloid body (AMY) plays important role in memory and learning processes. Projections of ghrelinergic neurons were identified in the AMY, and previously we verified that A-Ghr infused into basolateral nucleus of the AMY (ABL) caused liquid food intake decrease. The aim of the present study was to examine the possible effects of A-Ghr in the ABL on learning. Male Wistar rats were examined in two-compartment passive avoidance paradigm. Animals were shocked with 0.4mA current and subsequently were microinjected bilaterally with 50 or 100 ng A-Ghr, 30 ng GHS-R antagonist d-Lys3-GHRP-6 (ANT), ANT+50 ng A-Ghr (dissolved in 0.15M sterile NaCl/0.4 microl) or vehicle into the ABL. Fifty nanogram A-Ghr significantly increased the latency time, the 100 ng and the ANT alone were ineffective. The effect of 50 ng A-Ghr was eliminated by the ANT pretreatment. Our results suggest that intraamygdaloid A-Ghr enhances learning processes and memory in aversive situations, and this effect can specifically be prevented by ANT pretreatment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amygdala / drug effects*
  • Analysis of Variance
  • Animals
  • Avoidance Learning / drug effects*
  • Catheterization
  • Central Nervous System Agents / administration & dosage*
  • Electroshock
  • Ghrelin / administration & dosage*
  • Male
  • Memory / drug effects
  • Microinjections
  • Oligopeptides / administration & dosage
  • Rats
  • Rats, Wistar
  • Receptors, Ghrelin / antagonists & inhibitors
  • Time Factors

Substances

  • Central Nervous System Agents
  • GHRP-6, Lys(3)-
  • Ghrelin
  • Oligopeptides
  • Receptors, Ghrelin