Are changes in excitability in the hippocampus of adult male rats induced by prenatal methamphetamine exposure or stress?

Prenatal stress and drug exposure induce permanent alterations of the brain. Even though different brain structures are involved, alterations almost always refer to the hippocampus. The aim of this study was to investigate the excitability of hippocampal slices in low-magnesium epilepsy model of prenatally methamphetamine (MA, 5mg/kg sc.) or saline (sc., stress model) exposed animals in adult male rats. The second aim was to investigate, if a low dose of MA (1ml/kgs.c.) administered in adulthood changes the hippocampal activity of these animals. Adult Wistar male rats were divided into groups according to their prenatal treatment (C - naïve control; Sa - saline; MA - MA administration). One half of the animals was treated with a challenge dose of MA (1mg/kg sc.) 45min before hippocampal slices were cut. The activity of 350μ thick transversal slices of CA1 hippocampi was recorded (latencies of the first epileptiform discharge and the regular epileptiform activity) and evaluated in ACSF with low-magnesium concentration. Effects of prenatal exposure: The highest excitability was found in the Sa (prenatally stressed) group in respect to C and MA groups. This group developed also the highest number of seizure-like events. In addition, the prenatally MA treated group had also higher excitability than C group. Effects of the MA challenge dose: The challenge dose decreased the excitability of prenatally SA- exposed group. To conclude, even a mild prenatal stress significantly increases hippocampal excitability in adulthood and a challenge dose of MA is able to dampen it.