Relationship of orofacial movements to behavioural repertoire as assessed topographically over the course of 6-month haloperidol treatment followed by 4-month withdrawal.
BACKGROUND
Late-onset vacuous chewing movements (VCMs) arise in a significant proportion of rats treated chronically with conventional antipsychotic drugs. Given their common action to block dopamine D2-like receptors, VCMs may be related to changes in dopaminergic function; if so, other typical dopamine-mediated behaviours might be altered also.


OBJECTIVE
To examine this hypothesis, behavioural repertoire was studied topographically over the course of chronic treatment and withdrawal.


METHODS
Animals were injected with haloperidol decanoate 28 mg/kg IM, or vehicle, every 3 weeks for 27 weeks, and then maintained without treatment for a further 18 weeks. Immediately before each injection and during withdrawal, VCMs and other topographies of behaviour were assessed.


RESULTS
In both control and haloperidol-treated rats, exploratory behaviours declined over the study, indicating habituation effects. Conversely, VCMs emerged after 6 weeks of treatment with haloperidol and persisted after withdrawal; VCM and locomotion were not related, indicating that in treated rats, increased VCMs are not an artifact of reduced locomotion. Treated animals with VCMs evidenced increases in buccal tremor and grooming behaviour relative to those without VCMs, although no clear relationship to the emergence of VCMs was established; there were no material differences in any other topographies of behaviour.


CONCLUSIONS
The effect of long-term treatment with haloperidol to induce VCMs is not reflected in fundamental changes in dopamine-mediated behavioural topography but, rather, appears to affect neural mechanisms involved in orofacial movement preferentially.
De Souza
Ian E J
IE
Department of Anatomy, Royal College of Surgeons in Ireland, St. Stephen's Green, Dublin 2, Ireland.
Dawson
Niamh M
NM
Clifford
Jeremiah J
JJ
Waddington
John L
JL
Meredith
Gloria E
GE
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D018492:Dopamine Antagonists / Q000008:administration & dosage / Q000009:adverse effects* / Q000494:pharmacology; D004409:Dyskinesia, Drug-Induced / Q000503:physiopathology*; D005106:Exploratory Behavior / Q000187:drug effects; D006220:Haloperidol / Q000008:administration & dosage / Q000009:adverse effects* / Q000494:pharmacology; D008297:Male; D008409:Mastication / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*
D018492:Dopamine Antagonists; D006220:Haloperidol