Reversal of learned helplessness by morphine
in rats: involvement of a dopamine mediation
by
Besson A, Privat AM, Eschalier A, Fialip J
Laboratoire de Pharmacologie,
Faculte de Pharmacie,
Equipe NPPUA,
Clermont-Ferrand, France.
Pharmacol Biochem Behav 1998 Jun; 60(2):519-25

ABSTRACT

The aim of this study was to examine the role of dopamine neurotransmission in the effects of morphine in the learned helplessness paradigm in rats, a generally recognized model of depression. In this model, rats first exposed to inescapable shocks (stressed rats) exhibited an escape deficit in a subsequent shuttle-box test performed 48 h later for 3 consecutive days. The numbers of escape failures and intertrial crossings (motor activity during each intertrial interval) were recorded. Morphine was injected twice daily for 5 days (6 mg/kg/day, s.c.), and haloperidol, a preferential D2-dopamine receptor antagonist, was injected i.p. 15 min before each shuttle-box session. At the highest dose tested (150 microg/kg) haloperidol mimicked the behavioral deficit produced by inescapable shocks. A 37.5 microg/kg dose of haloperidol, which was ineffective by itself, reversed the morphine-induced improvement of escape behavior in previously stressed rats and the morphine-induced increase in intertrial activity in both stressed and nonstressed animals. These results support roles (a) for a dysregulation of dopaminergic neuronal activity in the expression of escape deficit subsequent to an inescapable aversive situation, and (b) for a dopaminergic mediation in the effects of morphine in the learned helplessness paradigm.

Opioids
Options
Dopamine
Anhedonia
Adenylyl cyclase
Drugs and reward
CRH-R antagonists
Animal depression
Social rank theory
Learned helpless rats
Glucocorticoids and mood
Depression and chronic pain
Depression, opioids and the HPA
Types of depression and mood-disorder
Imipramine and the delta opioid receptors

Refs
and further reading

HOME
HedWeb
Nootropics
cocaine.wiki
Future Opioids
BLTC Research
MDMA/Ecstasy
Superhapiness?
Utopian Surgery?
The Abolitionist Project
The Hedonistic Imperative
The Reproductive Revolution
Critique of Huxley's Brave New World

The Good Drug Guide
The Responsible Parent's Guide
To Healthy Mood Boosters For All The Family