Intracellular recordings were made from neurons of denervated superior cervical ganglion (SCG) of the rat. Focal electrical stimulation near the recording site evoked a monosynaptic inhibitory postsynaptic potential (IPSP) in about 15% of SCG neurons. The IPSP was reversibly abolished by alpha2-adrenoceptor antagonist, yohimbine. The ionic mechanism of the IPSP appeared to be due to an increase of potassium conductance following the activation of alpha2-adrenoceptor. Electron microscopic observations confirmed that these cells received synapses of intrinsic type. It was concluded that some SCG neurons were under an inhibitory control from neighboring neurons via noradrenergic synapses.
Animals Atropine