Vestibular-mediated synaptic inputs and pathways to sympathetic preganglionic neurons in the neonatal mouse.

摘要: To assess when vestibulosympathetic projections become functional postnatally, and to establish a preparation in which circuitry can be characterized more precisely, we used an optical approach record VIIIth nerve-evoked synaptic inputs thoracic sympathetic preganglionic neurons (SPNs) newborn mice. Stimulation of the nerve was performed isolated brainstem-spinal cord after retrogradely labelling with fluorescent calcium indicator Calcium Green 1-conjugated dextran amine, SPNs somatic motoneurons (MNs) (T) segments T2, 4, 6, 8, 10 12. Synaptically mediated responses could visualized recorded individual MNs, analysed respect latency, temporal pattern, magnitude pharmacology. stimulation evoked all MNs investigated. The SPN had onset latencies from 90 200 ms, compared much shorter were completely abolished by mephenesin, drug that preferentially reduces polysynaptic over monosynaptic transmission. Bicuculline picrotoxin, but not strychnine, increased magnitudes without changing latencies, suggesting convergence concomitant excitatory inhibitory inputs. Lesions strategically placed test involvement direct vestibulospinal pathways versus indirect within brainstem showed neonate are predominantly, if exclusively, latter. Thus, already at birth, connections reflex require ventrolateral medulla as adult mammals.