title: Histidine decarboxylase inhibition induced by alpha-fluoromethylhistidine provokes learning-related hypokinetic activity.
abstract: The influence of brain histamine (HA) on learning and memory is not well understood, although some reports indicate that HA improves memory consolidation. We have studied the effects of alpha-fluoromethylhistidine (FMH) (100 mg/Kg, i.p.), which reduced by 60-80% the concentration of hypothalamic HA, on rat locomotor activity (LA) and learning in several experimental conditions in a computerized system. FMH reduced LA in an open field paradigm (OFP) 3 h after injection and tended to inhibit motor habituation after a 3-day trial. In a maze paradigm (MP), where the animals had to learn to avoid a foot-shock (1 mA), FMH reduced LA, rearing (2F), and jumping activity (JA). The peripheral administration of HA to control-trained rats reduced a learning index (N/Sts ratio) by 50%. According to these results, FMH diminished LA, 2F, and JA with no effect on habituation in MP. These observations might indicate that a moderate reduction in the levels of brain HA might enhance attention in solving visuo-spatial tasks under stressful stimuli.
authors.affiliation: Department of Human Physiology, Madrid Complutense University Medical School, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Cacabelos
authors.forename: X A
authors.initials: XA
authors.lastname: Alvarez
mesh_terms: D000818:Animals; D005260:Female; D006633:Histamine Antagonists / Q000494:pharmacology*; D006640:Histidine Decarboxylase / Q000037:antagonists & inhibitors*; D007858:Learning / Q000187:drug effects / Q000502:physiology*; D008762:Methylhistidines / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D006633:Histamine Antagonists; D008762:Methylhistidines; C028309:alpha-fluoromethylhistidine; D006640:Histidine Decarboxylase