Intracerebellar Infusion Of An Mglur1/5 Agonist Enhances Eyeblink Conditioning

Cerebellar metabotropic glutamate receptor 1 (mGluR1) expressed by Purkinje cells may play an important role in learning-related cerebellar plasticity. Eyeblink conditioning (EBC) is a well-studied form of Pavlovian learning that engages discrete areas of cerebellar cortex and deep cerebellar nuclei. EBC is impaired in mGluR1 knockout mice. Here, we show that infusion of the mGluR1/5 agonist DHPG into the lobulus simplex region of cerebellar cortex facilitates EBC in rats. Infusion was made prior to Sessions 1 and 2 of EBC but the facilitatory effects persisted throughout subsequent, noninfusion sessions. The facilitatory effects were confined to frequency of eyeblink conditioned responses (CRs); there were no effects on amplitude or latency of CRs. There were also no effects on reflexive responding to the tone conditioned stimulus or eyelid stimulation unconditioned stimulus. The current results provide further evidence that cerebellar mGluR1 plays a role in cerebellar-dependent associative learning and complement previous studies using mGluR1 knockout mice.