Acute and rebound effects of lorazepam on orolingual motor function in young versus aged Fischer 344/Brown Norway rats.
The purpose of this study was to measure the acute effects of lorazepam [a short-acting benzodiazepine (BZ) with no active metabolites] on orolingual motor function in young (6 months) versus aged (24 months) Fischer 344/Brown Norway hybrid (F344/BN) rats. Rats licked water from an isometric force-sensing operandum so that the number of licks per session, licking rhythm (licks/second), and lick force could be measured during daily sessions. Acute doses (1.0 and 2.0 mg/kg) of lorazepam were administered 30 min before the testing sessions, 4 days apart. Whereas aged rats produced more licks per session, lorazepam increased this measure primarily in the young group. On the days after each lorazepam dose, rats licked less than they did before receiving the drug. This effect was shown by both groups. Aged rats showed significantly slower licking rhythm than young rats. Lorazepam slowed this measure in both groups. Peak tongue forces were significantly increased by lorazepam. These findings suggest that BZs such as lorazepam can affect tongue force output and exacerbate age-related tongue motility deficits. They also suggest that although BZs can directly influence motivation to engage in water-reinforced tasks, opposite 'rebound' effects may occur, even after acute dosing.
Zhang
Hongyu
H
Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
Stanford
John A
JA
D000367:Age Factors; D000818:Animals; D014151:Anti-Anxiety Agents / Q000633:toxicity*; D004327:Drinking Behavior / Q000187:drug effects*; D006824:Hybridization, Genetic; D008140:Lorazepam / Q000633:toxicity*; D008297:Male; D051381:Rats; D011914:Rats, Inbred BN / Q000235:genetics; D011916:Rats, Inbred F344 / Q000235:genetics; D011930:Reaction Time / Q000187:drug effects; D014059:Tongue / Q000187:drug effects
D014151:Anti-Anxiety Agents; D008140:Lorazepam