Excitation of inspiratory neurons by preinspiratory neurons in rat medulla in vitro.
In brain stem-spinal cord preparations isolated from newborn rats, we examined synaptic connections to inspiratory neurons from preinspiratory (Pre-I) neurons, by spike-triggered averaging. Potentials were simultaneously recorded intracellularly from inspiratory neurons, and extracellularly from Pre-I neurons in the ipsilateral ventrolateral medulla. The Pre-I neuron pulses were used to trigger computer averaging of potential changes. A total of 16 pairs were analyzed, and EPSP-like depolarizing potentials locked to the triggering Pre-I spikes were obtained from three pairs. Latency from the Pre-I spikes was 3.4-4.5 ms, and the amplitude was 0.07-0.4 mV. These connections were concluded to be monosynaptic, because the antidromic latency was 3.6 +/- 1.5 ms. The present results suggest the presence of excitatory synaptic connections from Pre-I neurons to inspiratory neurons in the ventrolateral medulla. These excitatory synaptic connections are probably important in the initiation of inspiratory burst activity.
Onimaru
H
H
Department of Physiology, Showa University School of Medicine, Tokyo, Japan.
Homma
I
I
Iwatsuki
K
K
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology / Q000379:methods; D005071:Evoked Potentials; D066298:In Vitro Techniques; D001239:Inhalation / Q000502:physiology*; D008526:Medulla Oblongata / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D012119:Respiration / Q000502:physiology*; D013569:Synapses / Q000502:physiology
D002118:Calcium