Journal of Neuroscience, Vol 7, 629-633, Copyright © 1987 by Society for Neuroscience
Population response of midbrain dopaminergic neurons to neuroleptics: further studies on time course and nondopaminergic neuronal influences
LA Chiodo and BS Bunney
In the present study, we examined the effects of the cholecystokinin
receptor antagonist, proglumide, on the depolarization-induced inactivation
of A9 and A10 dopaminergic neurons produced by repeated administration of a
classical antipsychotic drug (dopamine receptor antagonist). In addition,
we studied the nature of the effects of acute (1-48 hr) and long-term (7
month) treatment with the butyrophenone neuroleptic haloperidol on both the
basal firing rate and population response of dopamine-containing neurons in
these 2 regions. Acute oral administration of haloperidol (0.5 mg/kg)
results, within 1 hr of administration, in an increase in both the firing
rate and number of spontaneously active dopamine neurons encountered in
both A9 and A10 regions. These effects of a single treatment persist for a
minimum of 6 hr and, with respect to firing rate, are not completely
normalized for at least 24 hr. In contrast, 7 month continuous treatment
with haloperidol reduces the number of spontaneously active DA neurons
encountered in both regions in a manner similar to that observed at 21 d.
This effect is inferred to be due to the induction of depolarization-
induced inactivation of these neurons, since the acute administration of
the normally hyperpolarizing, direct-acting dopamine receptor agonist
apomorphine (64 micrograms/kg) immediately reverses this reduced number of
cells per track to near control levels. This effect appears to be dependent
on the continued presence of haloperidol since, when animals treated for 7
months are sampled 14 d after the cessation of drug administration,
spontaneous activity is no different from that observed in age-matched
controls.(ABSTRACT TRUNCATED AT 250 WORDS)