Deficits in behavioral sensitization and dopaminergic responses to methamphetamine in adenylyl cyclase 1/8-deficient mice.

Abstract

The cAMP/protein kinase A pathway regulates methamphetamine (METH)‐induced neuroplasticity underlying behavioral sensitization. We hypothesize that adenylyl cyclases (AC) 1/8 mediate these neuroplastic events and associated striatal dopamine regulation. Locomotor responses to METH (1 and 5 mg/kg) and striatal dopamine function were evaluated in mice lacking AC 1/8 (DKO) and wild‐type (WT) mice. Only 5 mg/kg METH induced an acute locomotor response in DKO mice, which was significantly attenuated versus WT controls. DKO mice showed a marked attenuation in the development and expression of METH‐induced behavioral sensitization across doses relative to WT controls. While basal and acute METH (5 mg/kg)‐evoked accumbal dialysate dopamine levels were similar between genotypes, saline‐treated DKO mice showed elevated tissue content of dopamine and homovanillic acid in the dorsal striatum (DS), reflecting dysregulated dopamine homeostasis and/or metabolism. Significant reductions in DS dopamine levels were observed in METH‐sensitized DKO mice compared to saline‐treated controls, an effect not observed in WT mice. Notably, saline‐treated DKO mice had significantly increased phosphorylated Dopamine‐ and cAMP‐regulated phosphoprotein levels, which were not further augmented following METH sensitization, as observed in WT mice. These data indicate that AC 1/8 are critical to mechanisms subserving drug‐induced behavioral sensitization and mediate nigrostriatal pathway METH sensitivity. Calcium/calmodulin‐stimulated adenylyl cyclase (AC) isoforms 1 and 8 were studied for their involvement in the adaptive neurobehavioral responses to methamphetamine. AC 1/8 double knockout (DKO) mice showed heightened basal locomotor activity and dorsal striatal dopamine responsivity. Conversely, methamphetamine‐induced locomotor activity was attenuated in DKO mice, accompanied by reductions in dopamine and HVA content and impaired DARPP‐32 activation. These findings indicate AC 1/8 signaling regulates the sensitivity of the nigrostriatal pathway subserving stimulant and neuroadaptive sensitizing effects of methamphetamine. 3‐MT, 3‐methoxytyramine; Ca2+, calcium; CaM, calmodulin; cdk5; cyclin‐dependent kinase 5; DA, dopamine; DARPP‐32, dopamine‐ and cAMP‐regulated phosphoprotein; D1R, dopamine D1 receptor; HVA, homovanillic acid; PKA, protein kinase A.