Synaptic inputs on rat brainstem motoneurones in organotypic slice culture

To study the formation of target specific afferents on brain stem motoneurones of the rat, we used an organotypic co-culture of embryonic rat (E18) brain stem explants containing the facial or hypoglossal motor nuclei together with a tongue explant. The brain stem explants also contained known dorsal premotor structures such as lateral reticular nuclei and vestibular or spinal trigeminal nuclei. In cultures maintained in vitro for over 3 weeks, silver impregnation studies identified neurones in the dorsal sensory structures with axons arborizing within the motor nucleus. A double fluorescent labelling procedure demonstrated that axons originating from dorsal sensory regions come in close contact with identified motoneurones. Electrical stimulation of neurones in the dorsal regions induced monosynaptic and polysynaptic EPSPs and spikes in identified motoneurones together with muscle contraction. This work demonstrates that premotor structures in slice cultures develop organotypic functional synaptic connections with embryonic brain stem motoneurones.