Effects of Diazepam, D-Amphetamine, and Morphine on Rats’ Choices Between Food Alone and Food with Delayed Shock

Abstract

Repeated choices that result in immediate reinforcing consequences followed by delayed aversive consequences are commonly associated with failures in “self-control”. The present study evaluated acute effects of diazepam, d-amphetamine, and morphine on rats’ choices using a variable-delay procedure that arranged choices involving conflicting-valence consequences. Rats pressed response levers to choose between a single-valence consequence (1 food pellet) and a conflicting-valence consequence (3 food pellets followed by a delayed shock). In each condition, the delay to shock varied systematically in a fixed sequence across blocks of trials of a session. After choice was stable, rats were exposed to acute administration of diazepam, damphetamine, and morphine. Effects of the drugs were shown by changes in patterns of choice of the single-valence consequence across the delays in each session, area under the curve, and response latencies. In sessions in baseline, following vehicle administration, and sessions conducted on the day before drug administrations, single-valence consequence choice was generally highest in blocks with short delays to shock and lowest in blocks with long delays, showing that effects of shock were an inverse function of the delay to shock. Following administration of diazepam, effects of shock on choice generally decreased, but this effect depended on the diazepam dose. Following administration of d-amphetamine, effects of shock on choice generally increased, but this effect depended on the d-amphetamine dose. Administration of morphine generally had no systematic effect on choice. This study sheds light on the general effects of commonly prescribed drug classes on choice in the conflicting-consequences paradigm.