Journal of Neuroscience, Vol 15, 7024-7036, Copyright © 1995 by Society for Neuroscience
Repeated treatment with haloperidol and clozapine exerts differential effects on dye coupling between neurons in subregions of striatum and nucleus accumbens
SP Onn and AA Grace
Department of Neuroscience, University of Pittsburgh, Pennsylvania 15260, USA.
The delayed onset of action of antipsychotic drugs (APDs) during the
treatment of schizophrenia has been hypothesized to temporally correlate
with the induction of depolarization block in rat mesencephalic dopamine
(DA) cell groups. Nevertheless, it is unknown whether these drugs also
exert a delayed action on the dopaminoceptive postsynaptic target cells in
the striatal complex. Using in vivo intracellular recording and dye
labeling techniques, the effects of APDs on dye coupling were examined in
subregions of the striatal complex defined by double staining for calbindin
immunoreactivity. Rats treated repeatedly with APDs were found to exhibit a
66-71% higher incidence of coupling that occurred in a drug- and a
region-specific manner, that is, both drug treatments increased dye
coupling in the limbic-associated accumbens shell region whereas only
haloperidol increased dye coupling in the motor-related striatal matrix and
accumbens core regions. In addition, cells located in regions in which dye
coupling was altered also showed significantly higher input resistance.
These changes were not observed in response to DA receptor blockade by
acute drug administration or when haloperidol was administered for a period
sufficient to induce DA receptor supersensitivity but not DA cell
depolarization block (i.e., 2 weeks). Therefore, alteration in dye coupling
appears to be correlated temporally with the induction of DA cell
depolarization block. The finding that both APDs exert a common action on
neurons in the accumbens shell region is consistent with its identification
as the site of therapeutic drug actions, whereas the capacity of
haloperidol to also affect cells in the motor-related matrix and core
regions correlates with its high propensity to induce extrapyramidal side
effects.