D-amphetamine enhances gustatory responses in brief access tests, but withdrawal does not produce gustatory anhedonia.

Abstract

Withdrawal from chronic d -amphetamine (AMPH), a putative animal model of anhedonia and depression, has been shown to reduce reward function, including operant and consummatory responses for 4% sucrose. However, a using microstructural analysis of licking for 4% sucrose, we found that AMPH withdrawal failed to alter measures associated with gustatory evaluation. To further explore the anhedonia hypothesis, we evaluated licking for sucrose in brief access tests before, during, and following AMPH treatment. Rats received a series of either 12 escalating AMPH doses (1–10 mg/kg, i.p.; n =10) or isotonic saline ( n =6) injections over 4 days. Licking for an array of 7 sucrose solutions (in M, 0, 0.015, 0.031, 0.062, 0.125, 0.25, and 0.5), presented randomly 4 times daily (20 s trials), was recorded starting 2 days before the start of AMPH/saline administration and ending 5 days after AMPH/saline withdrawal. Both AMPH and saline groups expressed sigmoidal concentration-licking functions, with no between-group differences in licking on baseline days ( p 's >0.23). Relative to saline, 3 days of AMPH treatment increased licking for 0.015, 0.031, and 0.0625 M sucrose, producing a left-shift in the concentration-licking curve. No significant decline in sucrose licking was observed after AMPH withdrawal. These results suggest that AMPH enhanced gustatory evaluation, but that the processes mediating AMPH withdrawal-induced behavioral suppressions are unrelated to the hedonic evaluation of palatable taste stimuli.