Cj. Slawecki et al., Effects of allopregnanolone on the EEG of alcohol-preferring and alcohol-nonpreferring rats, ALC CLIN EX, 24(9), 2000, pp. 1369-1375
Background: Alcohol preferring (P) and alcohol-nonpreferring (NP) rats have
been shown to have differing behavioral and electrophysiological responses
to drugs that are positive modulators of the gamma-aminobutyric acid type
A (GABA-A) receptor complex, such as ethanol and benzodiazepines. The neuro
active steroid allopregnanolone is also a positive modulator of GABA-A rece
ptors; therefore, we hypothesized that P and NP rats would respond differen
tly to intraperitoneally administered allopregnanolone.
Methods: Male P and NP rats were implanted with screw electrodes that overl
ay the frontal and parietal cortices and with a depth electrode aimed at th
e amygdala. Allopregnanolone (0.0-10.0 mg/kg ip) was administered 10 min be
fore recording the EEG.
Results: Allopregnanolone increased high-frequency power (8-32 Hz) in the c
ortex and amygdala of both P rats and NP rats. In addition, allopregnanolon
e increased the predominant frequency of the cortical EEG in the 8 to 16 Hz
bandwidth, decreased the predominant frequency in the 32 to 50 Hz bandwidt
h, and increased EEG variability (16-50 Hz). The effects of allopregnanolon
e were qualitatively similar in P and NP rats. However, P rats were more se
nsitive to low doses of allopregnanolone in cortex, whereas NP rats respond
ed to lower doses of allopregnanolone in the amygdala.
Conclusions: These data indicate that P and NP rats differ in their sensiti
vity to the EEG effects of allopregnanolone in the cortex and amygdala, whi
ch suggests that differences in GABAergic systems between P and NP rats may
contribute to some of the differences observed in their behavioral reperto
ire.