The neuronal endocannabinoid system is known to depress synaptic inputs retrogradely in an activity-dependent manner. This mechanism has been generally described for excitatory glutamatergic and inhibitory GABAergic synapses. Here, we report that neurones in the auditory brainstem of the Mongolian gerbil (Meriones unguiculatus) retrogradely regulate the strength of their inputs via the endocannabinoid system. By means of whole-cell patch-clamp recordings, we found that retrograde endocannabinoid signalling attenuates both glycinergic and glutamatergic post-synaptic currents in the same types of neurones. Accordingly, we detected the cannabinoid receptor 1 in excitatory and inhibitory pre-synapses as well as the endocannabinoid-synthesising enzymes (diacylglycerol lipase α/β, DAGLα/β) post-synaptically through immunohistochemical stainings. Our study was performed with animals aged 10–15 days, that is, in the time window around the onset of hearing. Therefore, we suggest that retrograde endocannabinoid signalling has a role in adapting inputs during the functionally important switch from spontaneously generated to sound-related signals.
We report retrograde endocannabinoid modulation of synaptic strength in auditory brainstem nuclei of the Mongolian gerbil. Utilising electrophysiological recordings and immunohistochemistry, we found endocannabinoid-dependent suppression of excitatory and inhibitory glycinergic currents in the same neurone types. We propose that retrograde endocannabinoid signalling contributes to adapting inputs to sound environment in the time period around the onset of functional hearing.