Intraamygdaloid microinjection of acylated-ghrelin influences passive avoidance learning

• Published in: Behavioural brain research Vol. 202; no. 2; pp. 308 - 311
• Main Authors: TOTH, Krisztian, LASZLO, Kristóf, LUKACS, Edit, LENARD, Laszló
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 14.09.2009; Elsevier
• Subjects: Amygdala - drug effects; Amygdaloid body; Analysis of Variance; Animals; Avoidance Learning - drug effects; Behavioral psychophysiology; Biological and medical sciences; Catheterization; Central Nervous System Agents - administration & dosage; Electroshock; Fundamental and applied biological sciences. Psychology; Ghrelin; Ghrelin - administration & dosage; Male; Memory; Memory - drug effects; Microinjections; Oligopeptides - administration & dosage; Passive avoidance learning; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rats, Wistar; Receptors, Ghrelin - antagonists & inhibitors; Time Factors; Ghrelin; Amygdaloid body; Memory; Passive avoidance learning; Learning; Acquisition process; Body; Avoidance; Appetite stimulant
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/j.bbr.2009.03.031

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 0.4 mA 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 0.15 M sterile NaCl/0.4 μl) 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.