TY - JOUR
T1 - Ketamine inhibits synaptic transmission and nicotinic acetylcholine receptor-mediated responses in rat intracardiac ganglia in situ
AU - Harper, Alexander A.
AU - Rimmer, Katrina
AU - Dyavanapalli, Jhansi
AU - McArthur, Jeffrey R.
AU - Adams, David J.
N1 - This work was supported by grants from the British Heart Foundation (A.A.H.) and National Health and Medical Research Council of Australia (D.J.A.). K. Rimmer was a Biotechnology and Biological Sciences Research Council, UK Research Student.
PY - 2020/3/15
Y1 - 2020/3/15
N2 - The intravenous anaesthetic ketamine, has been demonstrated to inhibit nicotinic acetylcholine receptor (nAChR)-mediated currents in dissociated rat intracardiac ganglion (ICG) neurons (Weber et al., 2005). This effect would be predicted to depress synaptic transmission in the ICG and would account for the inhibitory action of ketamine on vagal transmission to the heart (Inoue and König, 1988). This investigation was designed to examine the activity of ketamine on (i) postsynaptic responses to vagal nerve stimulation, (ii) the membrane potential, and (iii) membrane current responses evoked by exogenous application of ACh and nicotine in ICG neurons in situ. Intracellular recordings were made using sharp intracellular microelectrodes in a whole mount ICG preparation. Preganglionic nerve stimulation and recordings in current- and voltage-clamp modes were used to assess the action of ketamine on ganglionic transmission and nAChR-mediated responses. Ketamine attenuated the postsynaptic responses evoked by nerve stimulation. This reduction was significant at clinically relevant concentrations at high frequencies. The excitatory membrane potential and current responses to focal application of ACh and nicotine were inhibited in a concentration-dependent manner by ketamine. In contrast, ketamine had no effect on either the directly-evoked action potential or excitatory responses evoked by focal application of γ-aminobutyric acid (GABA). Taken together, ketamine inhibits synaptic transmission and nicotine- and ACh-evoked currents in adult rat ICG. Ketamine inhibition of synaptic transmission and nAChR-mediated responses in the ICG contributes significantly to its attenuation of the bradycardia observed in response to vagal stimulation in the mammalian heart.
AB - The intravenous anaesthetic ketamine, has been demonstrated to inhibit nicotinic acetylcholine receptor (nAChR)-mediated currents in dissociated rat intracardiac ganglion (ICG) neurons (Weber et al., 2005). This effect would be predicted to depress synaptic transmission in the ICG and would account for the inhibitory action of ketamine on vagal transmission to the heart (Inoue and König, 1988). This investigation was designed to examine the activity of ketamine on (i) postsynaptic responses to vagal nerve stimulation, (ii) the membrane potential, and (iii) membrane current responses evoked by exogenous application of ACh and nicotine in ICG neurons in situ. Intracellular recordings were made using sharp intracellular microelectrodes in a whole mount ICG preparation. Preganglionic nerve stimulation and recordings in current- and voltage-clamp modes were used to assess the action of ketamine on ganglionic transmission and nAChR-mediated responses. Ketamine attenuated the postsynaptic responses evoked by nerve stimulation. This reduction was significant at clinically relevant concentrations at high frequencies. The excitatory membrane potential and current responses to focal application of ACh and nicotine were inhibited in a concentration-dependent manner by ketamine. In contrast, ketamine had no effect on either the directly-evoked action potential or excitatory responses evoked by focal application of γ-aminobutyric acid (GABA). Taken together, ketamine inhibits synaptic transmission and nicotine- and ACh-evoked currents in adult rat ICG. Ketamine inhibition of synaptic transmission and nAChR-mediated responses in the ICG contributes significantly to its attenuation of the bradycardia observed in response to vagal stimulation in the mammalian heart.
KW - Action potential
KW - Anaesthesia
KW - Calcium channels
KW - Intrinsic cardiac ganglia
KW - Ketamine
KW - Nicotinic acetylcholine receptor
KW - Synaptic transmission
KW - Vagal nerve stimulation
UR - http://www.scopus.com/inward/record.url?scp=85077659517&partnerID=8YFLogxK
U2 - 10.1016/j.neuropharm.2019.107932
DO - 10.1016/j.neuropharm.2019.107932
M3 - Article
C2 - 31911104
SN - 0028-3908
VL - 165
JO - Neuropharmacology
JF - Neuropharmacology
M1 - 107932
ER -