Sensitivity and tolerance to autonomic effects of ethanol in adolescent and adult rats during repeated vapor inhalation sessions.
BACKGROUND
It is during adolescence that most drinkers initiate ethanol intake, with some of this use being excessive. One possible contributor to the increased ethanol consumption often seen during adolescence in humans and in various animal models is age differences in ethanol sensitivity and tolerance. The present study examined the impact of age on ethanol-related alterations in the autonomic nervous system.


METHODS
Sensitivity to the initial ethanol challenge and chronic tolerance as well as acute and protracted withdrawal-like phenomena were assessed in male adolescent and adult Sprague-Dawley rats, using implanted telemetry probes with ethanol delivered via vapor inhalation.


RESULTS
Both ages showed similar ethanol-induced tachycardia and activity suppression; however, adolescents were found to be more sensitive than adults to the hypothermic effect of ethanol, data opposite other results from our laboratory and elsewhere using intragastric intubations or intraperitoneal administrations of ethanol. Although little tolerance to ethanol's tachycardic or activity suppressant effects was seen after repeated ethanol inhalation sessions, chronic tolerance to ethanol's hypothermic effect developed faster in adults than in adolescents. A withdrawal-like syndrome, characterized by bradycardia and hypoactivity, typically emerged during the dark phase of the diurnal cycle after ethanol vapor exposure sessions. These effects were observed in animals of both ages, with the bradycardic effect more pronounced in adolescents.


CONCLUSIONS
In contrast to results indicating that adolescents may be less sensitive than adults to ethanol's hypothermic effect when ethanol is administered via bolus injection/intubation, adolescents appear more sensitive and develop tolerance to ethanol's hypothermic effects more slowly than adults when ethanol is administered at a more moderate rate via vapor inhalation.
Ristuccia
Robert C
RC
Center for Developmental Psychobiology, Department of Psychology, Binghamton University, Binghamton, New York 13902-6000, USA.
Spear
Linda P
LP
D000280:Administration, Inhalation; D000375:Aging / Q000523:psychology*; D000818:Animals; D001341:Autonomic Nervous System / Q000187:drug effects*; D001831:Body Temperature / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002492:Central Nervous System Depressants / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects; D004361:Drug Tolerance; D000431:Ethanol / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013375:Substance Withdrawal Syndrome / Q000523:psychology
D002492:Central Nervous System Depressants; D000431:Ethanol