Effects of propofol on spontaneous discharges of nociceptive-related neurons in hippocampal CA1 area of rats

Abstract

Objective To examine the effects of an intravenous general anaesthetics propofol on the discharges of nociceptive-related neurons in hippocampal CA1 area of rats, and to explore the mechanism of the antinociceptive action of propofol. Methods We established the models of extracellular recording of a single neuron of the hippocampal CA1 area in intact awake rats. Extracellular single-unit discharge recording technique was used to examine the effects ofpropofol （2 mg/kg） on the discharges of nociceptive-related neurons in hippocampal CA1 area. Results Of all the 55 neurons recorded in the CA1 area, three types were identified, namely nociceptive excitatory neurons （NENs, n=27）, nociceptive inhibitory neurons （NINs, n=13） and nociceptive unrelated neurons （NUNs, n=15）. Intravenous injection ofpropofol markedly lowered the discharge frequency for about 84.8% in 27 NENs, while significantly increased in 11 NINs （84.6%） for about 54.5%; and in 15 NUNs, 3 （20%） increased, 7 （46.7%） declined, while 5 （33.3%） showed no changes （amplitudes of variation〈20%） in the spontaneous discharge rates after the injection of propofol. Conclusion Propofol has specific modulation on nociceptive-related neurons in hippocampal CA1 area, which is, inhibiting the activity of the nociceptive excitatory neurons or enhancing the excitation of nociceptive inhibitory neurons; these may explain in part the mechanism of antinociceptive effects of propofol. Key words: Propofol; Hippocampus; Nociceptive-relatedneuron; Neurophysiology