Intraamygdaloid microinjection of acylated-ghrelin influences passive avoidance learning.
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.
Tóth
Krisztián
K
Institute of Physiology, Pécs University Medical School, Pécs, Hungary.
László
Kristóf
K
Lukács
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Lénárd
László
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D000679:Amygdala / Q000187:drug effects*; D000704:Analysis of Variance; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D002404:Catheterization; D002491:Central Nervous System Agents / Q000008:administration & dosage*; D004597:Electroshock; D054439:Ghrelin / Q000008:administration & dosage*; D008297:Male; D008568:Memory / Q000187:drug effects; D008845:Microinjections; D009842:Oligopeptides / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D054440:Receptors, Ghrelin / Q000037:antagonists & inhibitors; D013997:Time Factors
D002491:Central Nervous System Agents; C520836:GHRP-6, Lys(3)-; D054439:Ghrelin; D009842:Oligopeptides; D054440:Receptors, Ghrelin