Amphetamine-induced rapid-onset sensitization: role of novelty, conditioning and behavioral parameters.
BACKGROUND
Environmental factors may modulate sensitization to the locomotor-activating effects of psychostimulants. In addition, some parameters of locomotor activity seem to be more sensitive to detect cocaine-induced behavioral sensitization. We examined how novelty and conditioning can modulate a previously described rapid-onset type of behavioral sensitization to amphetamine (AMP) in mice, using total, peripheral and central open-field locomotion frequencies as experimental parameters.


METHODS
In the first experiment, mice received an ip injection of saline (SAL) or 5.0 mg/kg AMP paired or not with the open-field or in their home-cages. Four hours later, all the animals received an ip SAL challenge injection and, 15 min later, were observed in the open-field for quantification of total, peripheral and central locomotion frequencies. The second experiment had a similar protocol, except that mice received a challenge injection of 1.5 mg/kg AMP.


RESULTS
The priming AMP injection significantly increased all the parameters of locomotion of SAL-challenged mice firstly exposed to or previously paired (but not unpaired) with the open-field. AMP priming injection enhanced total and peripheral locomotion of all AMP-challenged mice but only increased central locomotion of mice submitted to novelty or environmental conditioning.


CONCLUSIONS
Our results showed: 1) the development of an AMP-induced rapid-onset sensitization to novelty and rapid-onset environmental conditioning in mice, 2) the potentiation of the AMP-induced rapid-onset sensitization to an AMP challenge injection by novelty and environmental conditioning and 3) the importance of measuring different locomotor activity parameters in behavioral sensitization experiments.
Alvarez
Juliana do Nascimento
Jdo N
Department of Pharmacology, Universidade Federal de São Paulo, São Paulo, Brazil.
Fukushiro
Daniela Fukue
DF
Tatsu
Julie Anne Obara
JA
de Carvalho
Erika Pereira
EP
Gandolfi
Ana Camila de Castro
AC
Tsuchiya
Joyce Borges
JB
Carrara-Nascimento
Priscila Fernandes
PF
Lima
Melina Lopes
ML
Bellot
Rogério Gentil
RG
Frussa-Filho
Roberto
R
D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003213:Conditioning, Psychological / Q000187:drug effects*; D005106:Exploratory Behavior / Q000187:drug effects*; D005260:Female; D051379:Mice; D009043:Motor Activity / Q000187:drug effects
D000661:Amphetamine