Naltrexone does not disrupt acquisition or performance of inhibitory conditioning

Abstract

Previous research has demonstrated that naltrexone (NTX) enhances acquisition of aversive excitatory Pavlovian conditioning. Both the conditional opponent theory (Schull, 1979) and the perceived intensity hypothesis (Fanselow, 1981;Young & Fanselow, 1992) accurately predict this result. Nevertheless, these two models make different predictions about the effects of NTX on inhibitory conditioning. In the present experiment, these predictions were tested by investigating the effect of NTX on the acquisition ana expression of inhibitory conditioning. NTX was injected during conditioned inhibitory (CI) training or testing. To avoid an effect of NTX on excitatory conditioning, excitatory and inhibitory trials were separated by 24 h. A control group was used to assess acquisition of CI. It was found that NTX did not disrupt acquisition or expression of CI. These results are inconsistent with the conditional opponent theory but are in accordance with the perceived intensity hypothesis.Treatment with opioid antagonists during training involving aversive stimulation , such as footshock, causes an increase in acquisition of fear conditioning (Ehrman, Josephson, Schull, & Sparich , 1979;Fanselow & Bolles, 1979;Gallagher & Kapp, 1978). Two models of aversive Pavlovian conditioning-the conditioned opponent theory developed by Schull (1979) and the perceived intensity hypothesis developed by Fanselow (1981Fanselow ( , 1984aYoung & Fanselow, 1992)-offer distinct accounts of this result.The conditioned opponent process theory proposes that an aversive stimulus produces its primary hedonic reaction, a-process, followed by an opposite hedonic response, b-process . This b-process functions to reduce the primary hedonic reactions produced by the aversive stimulus. This process is assumed to be mainly a conditional response that grows with consecutive presentations of the aversive stimulus. The animal's affective state in response to the aversive stimulus is a summation of these two opposite processes . When the a-process is bigger than the bprocess, an A-state results; when the b-process is bigger than the a-process, a B-state results. The A-state is responsible for Pavlovian fear conditioning and has its maximum efficacy when the aversive stimulus is presented for the first time. With successive aversive stimulation, the bprocess increases, causing a reduction in the A-state. The conditioned opponent theory suggests that endogenous

The structure of individual differences in batteries of rapid acquisition tasks in mice.

“…Other findings suggest that these two aspects of training respond similarly to the same experimental interventions (cf. Landeira-Fernandez, Fanselow, DeCola, & Kim, 1993, and Verrico, Jentsch, Roth, & Taylor, 2004, with Jakubowska, Gumusbas, & Kara, 2003, and Nikkhah, Rosenthal, Hedrich, & Samii, 1998). These studies all measured behavior at two different points in training to determine the relationship between acquisition and performance.…”