title: Direct connection of the nucleus reticularis gigantocellularis neurons with neck motoneurons in cats.
abstract: Functional connections of single reticulospinal neurons (RSNs) in the nucleus reticularis gigantocellularis (NRG) with ipsilateral dorsal neck motoneurons were examined with the spike-triggered averaging technique. Extracellular spikes of single NRG-RSNs activated antidromically from the C6, but not from the L1 segment (C-RSNs) were used as the trigger. These neurons were monosynaptically activated from the superior colliculus and the cerebral peduncle. Single-RSN PSPs were recorded in 43 dorsal neck motoneurons [biventer cervicis and complexus (BCC) and splenius (SPL)] for 21 NRG-RSNs and 135 motoneurons tested. All synaptic potentials were EPSPs, and most of their latencies, measured from the triggering spikes, were 0.8-1.5 ms, which is in a monosynaptic range. The amplitudes of single-RSN EPSPs were 10-360 microV. Spike-triggered averaging revealed single-RSN EPSPs in multiple motoneurons of the same species (SPL or BCC), their locations extending up to nearly 1 mm rostrocaudally. Synaptic connections of single RSNs with both SPL and BCC motoneurons were also found with some predominance for one of them. The results provide direct evidence that NRG-RSNs make monosynaptic excitatory connections with SPL and BCC motoneurons. It appears that some NRG-RSNs connect predominantly with SPL motoneurons and others with BCC motoneurons.
authors.affiliation: Department of Neurophysiology, Tokyo Metropolitan Institute for Neuroscience, 2-6 Musashidai, Fuchu-shi, Tokyo 183-8526, Japan. shigeto@tmin.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Sasaki
mesh_terms: D000818:Animals; D002415:Cats; D019706:Excitatory Postsynaptic Potentials; D007839:Functional Laterality; D008526:Medulla Oblongata / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology*; D009333:Neck; D011149:Pons / Q000502:physiology*; D011930:Reaction Time; D013116:Spinal Cord / Q000502:physiology*; D013569:Synapses / Q000502:physiology*