Increases in extracellular levels of 5-HT and dopamine in the basolateral, but not in the central, nucleus of amygdala induced by aversive stimulation of the inferior colliculus.
Consistent evidence has shown that dopamine release in the prefrontal cortex is increased by electrical stimulation of the inferior colliculus (IC) as unconditioned stimulus. Recent reports have also demonstrated that inactivation of the basolateral nucleus of the amygdala (BLA) with muscimol enhances the behavioural consequences of the aversive stimulation of the IC and reduces the dopamine release in the prefrontal cortex. Moreover, neurotoxic lesions of the BLA enhance whereas those of the central nucleus of the amygdala (CeA) reduce the aversiveness of the electrical stimulation of the IC. Based on these findings the present study examined the effects of the electrical stimulation of the IC on the extracellular levels of serotonin and dopamine in the BLA and CeA. To this end, rats implanted with a stimulation electrode in the IC also bore a microdialysis probe in the BLA or CeA for determination of the release of dopamine and serotonin. IC electrical stimulation at the freezing and escape thresholds increased the levels of serotonin ( approximately 70%) and dopamine ( approximately 60%) in the BLA related to the basal values. Similarly, the metabolites DOPAC and 5-HIAA increased in a parallel fashion in BLA. No significant changes could be detected in these biogenic amines and metabolites in CeA following IC aversive stimulation. These findings point to a differential role of serotonergic and dopaminergic mechanisms of the BLA and CeA in the setting up of adaptive responses to fear states generated at the inferior colliculus level.
Macedo
Carlos Eduardo
CE
Laboratório de Psicobiologia, Faculdade Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo (USP) 14040-901, Ribeirão Preto, SP Brazil.
Martinez
Raquel Chacon Ruiz
RC
de Souza Silva
Maria Angélica
MA
Brandão
Marcus Lira
ML
D000679:Amygdala / Q000033:anatomy & histology / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D001362:Avoidance Learning / Q000502:physiology / Q000528:radiation effects; D001522:Behavior, Animal; D015306:Biogenic Monoamines / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004298:Dopamine / Q000378:metabolism*; D004558:Electric Stimulation / Q000009:adverse effects / Q000379:methods; D004924:Escape Reaction / Q000502:physiology / Q000528:radiation effects; D005110:Extracellular Space / Q000378:metabolism* / Q000528:radiation effects; D007245:Inferior Colliculi / Q000502:physiology* / Q000528:radiation effects; D008297:Male; D017551:Microdialysis / Q000379:methods; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism*; D013997:Time Factors
D015306:Biogenic Monoamines; D012701:Serotonin; D004298:Dopamine