Ma. Whittington et al., MORPHINE DISRUPTS LONG-RANGE SYNCHRONY OF GAMMA-OSCILLATIONS IN HIPPOCAMPAL SLICES, Proceedings of the National Academy of Sciences of the United Statesof America, 95(10), 1998, pp. 5807-5811
Oscillations in neuronal population activity within the gamma frequenc
y band (>25 Hz) have been correlated with cognition: Gamma oscillation
s could bind together features of a sensory stimulus by generating syn
chrony between discrete cortical areas [Eckhorn, R., Bauer, R., Jordan
, W., Brosch, M., Kruse, W., Munk, M. & Reitboeck, H. J. (1989) Biol,
Cybern. 60, 121-130; Singer, W. & Gray, C.;M. (1995) Annu. Rev. Neuros
ci, 18, 555-556], Herein me demonstrate that morphine and beta-endorph
in disrupt this long-range synchrony of gamma oscillations while leavi
ng the synchrony of local oscillations relatively intact. The effect i
s caused by a decrease in type A gamma-aminobutyric acid receptor-medi
ated inhibition of both excitatory pyramidal cells and inhibitory inte
rneurons, The effects of morphine on gamma oscillations were blocked b
y mu-opioid receptor antagonists but not by antagonists of delta or ka
ppa receptors, Morphine also produced burst firing in interneurons, be
cause synaptic excitation from pyramidal cells was no longer balanced
by synchronous inhibitory postsynaptic potentials, The loss of synchro
ny of gamma oscillations induced by morphine may constitute one mechan
ism involved in producing the cognitive deficits that this drug causes
clinically.