Intraamygdaloid microinjections of acylated/ghrelin influences passive avoidance learning.

Tóth, Krisztián and László, Kristóf and Lukács, Edit Éva and Lénárd, László (2009) Intraamygdaloid microinjections of acylated/ghrelin influences passive avoidance learning. BEHAVIOURAL BRAIN RESEARCH, 202. pp. 308-311. ISSN 0166-4328

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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 ratswere examined in two-compartment passive avoidance paradigm. Animalswere 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/0.4μl) 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.

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