Lack of midazolam-induced anxiolysis in the plus-maze Trial 2 is dependent on the length of Trial 1.
The influence of the first exposure length upon the effect of midazolam (MDZ) administration prior to the second exposure in the elevated plus-maze (EPM) was investigated. Drug-free rats were assigned to freely explore the EPM for 1, 2 or 5 min (Trial 1). Twenty-four hours later, each group was subdivided in two further groups, which were retested in the EPM for 5 min, 30 min after either saline or MDZ (1.5 mg kg(-1)) administration (Trial 2). The data showed that during Trial 2, the percentage of entries (%Open arm entries) and time spent in the open arms (%Open arm time) were decreased if rats were pre-exposed to the EPM for 2- or 5-min Trial 1, while the group submitted to 1-min Trial 1 length displayed decreased %Open arm time only. The anxiolytic effect of MDZ prior to Trial 2 was present in the group submitted to 1-min, impaired in the group submitted to 2-min and absent in the group submitted to 5-min Trial 1 length. Data are analyzed taking into account the emotional learning which underlies the exploratory behavior during the EPM Trial 2.
Dal-Cól
M L C
ML
Department of Physiological Sciences, Centre of Biological Sciences, Federal University of Santa Catarina, 88, 040-900, Florianópolis, SC, Brazil.
Pereira
L Orlandi
LO
Rosa
V P
VP
Calixto
A V
AV
Carobrez
A P
AP
Faria
M S
MS
D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001007:Anxiety / Q000523:psychology*; D001522:Behavior, Animal / Q000187:drug effects; D005106:Exploratory Behavior / Q000187:drug effects; D008297:Male; D008874:Midazolam / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar
D014151:Anti-Anxiety Agents; D008874:Midazolam