NEUROLEPTIC-INDUCED CHEWING MOVEMENTS IN THE RAT ARE SUPPRESSED BY PERIPHERALLY BUT NOT CENTRALLY ADMINISTERED CCK AND ABOLISHED BY BILATERAL SUBDIAPHRAGMATIC VAGOTOMY
Aj. Stoessl et E. Polanski, NEUROLEPTIC-INDUCED CHEWING MOVEMENTS IN THE RAT ARE SUPPRESSED BY PERIPHERALLY BUT NOT CENTRALLY ADMINISTERED CCK AND ABOLISHED BY BILATERAL SUBDIAPHRAGMATIC VAGOTOMY, Neuropharmacology, 32(6), 1993, pp. 555-560
We have previously demonstrated that intraperitoneal cholecystokinin (
CCK-8S) suppresses the vacuous chewing mouth movements (VCM's) elicite
d by chronic neuroleptic administration in the rat, a possible model o
f tardive dyskinesia (TD) in humans. The studies described here were u
ndertaken in order to better determine whether this effect is mediated
centrally or peripherally. In the first set of experiments, CCK-8S (1
0, 30 or 50 ng, i.c.v.) was found to have no effect on VCM's elicited
by 20 weeks treatment with fluphenazine decanoate (25 mg/kg, i.m., eve
ry 3 weeks). A second set of experiments was then performed to determi
ne if the previously observed effects of intraperitoneal CCK-8S were v
agally mediated. As previously described, CCK-8S (10, 30 or 60 mug/kg,
i.p.) suppressed neuroleptic-induced VCM's in sham-operated animals w
ithout affecting the baseline VCM rate. Bilateral subdiaphragmatic vag
otomy alone unexpectedly suppressed neuroleptic-induced VCM's to contr
ol levels and CCK-8S had no further effect. Vagotomy also prevented th
e suppressive effects of peripherally administered CCK-8S on rearing a
nd grooming. We conclude that neuroleptic-induced VCM's may depend upo
n tonic activity in the vagus nerve and/or its central projections and
that the effects of CCK-8S on this behavioural response are likely to
be peripherally mediated.