Effects of chronic naloxone administration on vacuous chewing movements and catalepsy in rats treated with long-term haloperidol decanoate

Michael F. Egan, Jennifer N. Ferguson, Thomas M. Hyde

Research output: Contribution to journalArticle

Abstract

Most antipsychotic medications produce motoric side effects, including parkinsonism and tardive dyskinesia (TD). Correlates of these behaviors in rats (catalepsy and vacuous chewing movements, respectively) were used as a model to assess the usefulness of chronic naloxone administration in symptom reduction. Previous studies have suggested that increased neurotransmission in the endogenous opioid system modulates neuroleptic-induced motoric side effects. Rats were treated with haloperidol decanoate or vehicle for 27 weeks, and withdrawn for 30 weeks. Subsequently, naloxone (0.5 to 2.0 mg/kg SC twice daily) was given for 5 weeks. Long-term haloperidol treatment produced a syndrome of vacuous chewing movements (VCMs) that persisted during the drug withdrawal period. Catalepsy developed rapidly and also persisted. Naloxone treatment had little effect on VCMs but increased catalepsy scores in both haloperidol and vehicle treated groups. Naloxone reduced rearing and grooming in haloperidol rats while increasing these measures in vehicle treated rats. The results indicate that neuroleptic-induced motoric side effects are not reversed by naloxone in rats. Furthermore, they suggest that increased opioid neurotransmission may not underlie the expression of VCMs. This does not rule out the possibility that endogenous opioid system may be involved in the development of VCMs. To the extent that this animal model is valid, naloxone may not be effective in treating TD and neuroleptic-induced parkinsonism in humans.

Original languageEnglish (US)
Pages (from-to)355-363
Number of pages9
JournalBrain Research Bulletin
Volume38
Issue number4
DOIs
StatePublished - 1995
Externally publishedYes

Keywords

  • Haloperidol
  • Naloxone
  • Tardive dyskinesia
  • Vacuous chewing movements

ASJC Scopus subject areas

  • Neuroscience(all)

Fingerprint Dive into the research topics of 'Effects of chronic naloxone administration on vacuous chewing movements and catalepsy in rats treated with long-term haloperidol decanoate'. Together they form a unique fingerprint.

  • Cite this