Premium
VENTRAL MEDULLARY CHEMORECEPTOR INPUTS TO NEURONS WITHIN THE NUCLEUS AMBIGUUS
Author(s) -
Lewis DI
Publication year - 1998
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1998.tb02239.x
Subject(s) - excitatory postsynaptic potential , neuroscience , hyperpolarization (physics) , depolarization , chemistry , acetylcholine , nucleus ambiguus , membrane potential , cholinergic neuron , cholinergic , biophysics , biology , inhibitory postsynaptic potential , medulla oblongata , central nervous system , endocrinology , organic chemistry , nuclear magnetic resonance spectroscopy
SUMMARY 1. The neural mechanisms by which neurons within the nucleus ambiguus respond to chemoreceptor stimuli applied to the ventral medullary surface (VMS) were investigated by determining the effect of low pH on the membrane potential and synaptic activity of these neurons in vitro. 2. Small reductions in pH evoked an indirect membrane depolarization and/or an increase in excitatory synaptic activity in the majority of neurons. A direct membrane hyperpolarization was observed in the remaining neurons. 3. Acetylcholine evoked a direct nicotinic receptor‐mediated membrane depolarization in these neurons. In addition, 37% of neurons received muscarinic synaptic input that originated from neurons located near the VMS. 4. Low‐pH artificial cerebrospinal fluid (aCSF) potentiated the cholinergic component of the excitatory post‐synaptic potential (EPSP) evoked from near the VMS. Both this EPSP and the spontaneous EPSP evoked by low‐pH aCSF could be blocked by atropine. 5. It is concluded that at least two different mechanisms exist to transmit chemoreceptive information from the VMS to neurons within the nucleus ambiguus. In the majority of neurons, an indirect excitatory response is observed that is due, in part, to activation of a polysynaptic cholinergic pathway originating near the VMS. In the remaining neurons, low pH evokes a hyperpolarization that is due to a direct action of the dendrites of the neurons themselves that project near to the VMS.