Influence of epipregnanolone on the modulation of rapid tolerance to ethanol by neurosteroids.
OBJECTIVE
The objective of the present study was to investigate the effect of epipregnanolone on the influence of neurosteroids on the development of rapid tolerance to the motor impairing and hypothermic effects of ethanol.


METHODS
Experiment 1: on Day 1 groups of mice were pretreated with saline or with epipregnanolone. After 30 min each group was further divided in subgroups that received ethanol or saline. Thirty, 60 and 90 min after the injections the animals were tested on the rota-rod or the body temperature was measured. On Day 2 all groups received ethanol and a similar procedure was followed to evaluate rapid tolerance. Experiment 2 and 3: On Day 1 groups of mice were treated with epipregnanolone and after 15 min each group was divided into three groups in order to receive pregnenolone sulfate, dehydroepiandrosterone sulfate or saline. Thirty minutes later, each group was further divided into two subgroups in order to receive ethanol or saline, respectively, and 30, 60 and 90 min later the animals were tested as in the experiment 1. On Day 2 all groups received ethanol and a similar procedure was followed to evaluate rapid tolerance.


RESULTS
Pretreatment with epipregnanolone (0.10-0.30 mg/kg) significantly blocked the development of tolerance to the motor impairing and hypothermic effects induced by ethanol in mice. Considering tolerance to ethanol-induced motor impairment, epipregnanolone (0.15 mg/kg) reversed the stimulatory action of dehydroepiandrosterone sulfate (0.15 mg/kg), but did not affect the actions of pregnenolone sulfate (0.08 mg/kg). Moreover, epipregnanolone prevented the inhibitory action of allotetrahydrodeoxycorticosterone (0.10 mg/kg). In relation to ethanol-induced hypothermia, the results showed that pretreatment with epipregnanolone (0.30 mg/kg) significantly prevented the stimulatory action of dehydroepiandrosterone sulfate and pregnenolone sulfate, as well as the inhibitory action of allotetrahydrodeoxicorticosterone (0.20 mg/kg), on tolerance to this effect.


CONCLUSIONS
The results suggest a differential interaction between neurosteroids that might modulate the development of rapid tolerance to ethanol.
Barbosa
Adriana Dias Elpo
AD
CCS, Universidade do Vale do Itajaí, Itajaí, SC, Brasil. adrielpo@univali.br
Morato
Gina Struffaldi
GS
D000704:Analysis of Variance; D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D003900:Desoxycorticosterone / Q000031:analogs & derivatives / Q000494:pharmacology; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical; D004347:Drug Interactions; D004361:Drug Tolerance; D000431:Ethanol / Q000494:pharmacology*; D007035:Hypothermia / Q000139:chemically induced*; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects*; D011280:Pregnanolone / Q000494:pharmacology*; D011284:Pregnenolone / Q000494:pharmacology
D000777:Anesthetics; D002492:Central Nervous System Depressants; C018370:pregnenolone sulfate; D000431:Ethanol; D003900:Desoxycorticosterone; C009413:tetrahydrodeoxycorticosterone; D011284:Pregnenolone; D011280:Pregnanolone