Role of endocannabinoid and GABAA receptor in modulating synaptic plasticity in the vestibular nucleus of postnatal rats

Abstract

Endocannabinoid (eCB) has emerged as the key form of activity-dependent long-term presynspatic plasticity in the amygdala, hippocampus and visual cortex. eCB receptors are found to express in the vestibular nucleus but the role of eCB on long-term depression of inhibitory responses (iLTD) in central vestibular neurons remains unaddressed. Whole-cell patch-clamp experiments were therefore conducted on medial vestibular neurons in brainstem slices of postnatal rats (P5─15). iLTD of GABAA receptor-mediated evoked-IPSCs could be induced in these central vestibular neurons with theta-burst stimulation delivered to the vestibular afferents. In P5─7 rats, iLTD could be induced in 80% of the medial vestibular neurons tested. In P8─15 rats, however, iLTD could only be induced in 30% of the neurons tested. Application of antagonist of type 1 cannabinoid receptor (AM251) decreased the probability of iLTD induction to 30% in rats aged P5 to P7, while treatment with agonist of type 1 cannabinoid receptor (WIN55) increased the probability to 70% in rats aged P8 to P10. These results indicate that eCB modulates the efficacy of GABAergic synapses in the vestibular nucleus in an age-dependent role manner.