Aberrant Behavioral Sensitization by Methamphetamine in Junctophilin-Deficient Mice

Junctophilins (JPs) expressed in the endoplasmic/sarcoplasmic reticulum (ER/SR) interact with the plasma membrane, thereby constructing junctional membrane complexes (JMC). We here reported that double-knockout mice lacking both JP3 and JP4 (JP-DKO mice) exhibit aberrant synaptic plasticity in the corticostriatal circuits and irregular methamphetamine (METH)-induced behavioral sensitization when METH (1.0 mg/kg) was administrated six consecutive days and assessed the striatal glutamatergic population spike (PS) by stimulation of cortical white matter. When we assessed the striatal PS by stimulation of cortical white matter, the long-term depression (LTD) was observed in JP-DKO mouse striatum similar to that in control (JP-double hetero mice (JP-DHE mice)). Importantly, LTD converted to long-term potentiation (LTP) following chronic METH treatment concomitant with behavioral sensitization in JP-DHE mice. LTD in JP-DKO mice, however failed to convert to LTP with lacks of behavioral sensitization. LTP impairment in JP-DKO mice was restored by pretreatment with FK506, calcineurin (CaN) inhibitor, but not with apamin, SK channel inhibitor. In immunoblotting analyses, calcium/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation was significantly increased following METH treatment in the striatum of JP-DHE mice. However, CaMKII autophosphorylation did not changed by METH treatment in the striatum of JP-DKO mouse. The increased CaMKII autophosphorylation was closely associated with elevated CaN activity in JP-DKO mice. The lack of increased CaMKII activity in JP-DKO mice was correlated with the impaired METH-induced behavioral sensitization. Thus, elevated CaN and aberrant CaMKII activities in the striatum of JP-DKO mice likely accounts for lack of METH-induced behavioral sensitization.