| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 6259649 | Behavioural Brain Research | 2012 | 4 Pages |
The 50Â kHz ultrasonic vocalisations (USVs) that are emitted by rats are dependent on activity of dopaminergic neurons projecting from the ventral tegmental area to the limbic and cortical structures. According to many experimental data, emission of the 50Â kHz USV reflects a positive emotional state. The appetitive calls are also emitted in response to the administration of drugs of abuse, e.g., cocaine or amphetamine (AMPH), or in a reply to a positively conditioned context. However, there is no strong evidence in the literature that morphine can also modulate 50Â kHz USVs. The aim of this paper is to study the effects of morphine and morphine-conditioned context on 50Â kHz USVs, using spontaneously or drug-modulated 50Â kHz USVs. Our results showed that acute administration of morphine to rats after withdrawal period inhibited the emission of 50Â kHz USVs. The stimulating effect of morphine-conditioned context on 50Â kHz USVs appeared on the post-withdrawal challenge day immediately before drug injection, 14 days after the last episode of morphine-induced context conditioning. The context-induced 50Â kHz USVs can be used as a sensitive test for drug dependency. The current study also shows that 50Â kHz USVs can be useful tool for studying the mechanisms of long lasting central effects of morphine.
⺠Acute administration of morphine inhibits the emission of 50-kHz USVs in rats. ⺠The rewarding effect of morphine appears on the challenge day before drug injection. ⺠The context-induced 50-kHz USVs can be used as a sensitive test for drug dependency.
