Journal of Neuroscience, Vol 6, 2245-2251, Copyright © 1986 by Society for Neuroscience
Differential down-regulation of D1-stimulated adenylate cyclase activity in rat forebrain after in vivo amphetamine treatments
JM Roberts-Lewis, PH Roseboom, LM Iwaniec and ME Gnegy
Amphetamine has complex behavioral actions in the rat that depend upon the
release of dopamine in striatal and mesolimbic brain regions. To explore a
possible role of the dopamine-sensitive cAMP second-messenger system in
mediating these effects, we examined the effects of in vivo amphetamine
treatments on the D1 receptor-coupled adenylate cyclase system in membranes
from striatal and mesolimbic rat brain regions. The results show that
amphetamine produces a regional, dose- and time- dependent down-regulation
of adenylate cyclase activity. Intermediate and high doses of amphetamine
(2.5 and 7.5 mg/kg, respectively), but not a low dose (1.0 mg/kg), resulted
in a decrease in the apparent Vmax and/or an increase in the apparent Ka
for the selective D1 partial agonist, SKF38393, in striatal membranes 30
min after amphetamine treatment. Treatment of rats with 7.5 mg/kg
amphetamine for 30 and 60 min, but not 10 min, similarly resulted in a
down-regulation of D1- mediated adenylate cyclase activity in striatal
membranes. In contrast, in mesolimbic tissues, no amphetamine treatment at
any time resulted in an alteration of SKF38393-stimulated adenylate cyclase
activity relative to saline controls. The results of behavioral analyses
also showed that animals exhibiting intense stereotypies had significantly
lower striatal apparent Vmax values than did those animals engaged in
moderate or no behavioral activity at the time of decapitation. These
findings demonstrate that amphetamine treatments result in a down-
regulation of striatal, but not mesolimbic, dopamine-sensitive adenylate
cyclase activity that parallels the intense, stereotyped behaviors
characteristic of dopaminergic activation in the striatum.