Intracellular and extracellular motor neuron activity underlying rhythmic respiration inLimulus

Abstract

1. Intracellular activity was recorded from respiratory motor neurons and other neurons in the isolated abdominal CNS ofLimulus. 2. Patterned motor output underlying the gill ventilatory rhythm occurred in isolated preparations. Stimulation of tracts in interganglionic connectives and of various roots and connectivies elicited the rhythmic output. Rhythmic respiratory activity could also occur in the absence of any stimulation. 3. During cyclic activity the membrane potentials of motor and other neurons oscillated along with the rhythmic motor output (Fig. 3). In some cells, membrane repolarization could be reversed by hyperpolarizing current (Figs. 4, 6), indicating that bursts were terminated by synaptic inhibition. 4. Changing impulse frequencies of neurons by current injection or by antidromic stimulation had little effect on activity of other motor neurons (Fig. 4, 6, 7). There was no evidence to implicate connections between motor neurons in the generation of the rhythm, but the existence of such connections cannot be ruled out.