beta-Endorphin induces general anaesthesia by an interaction with opiate receptors

beta-endorphin, administered into the cerebral ventricles of rats, provokes a sequence of behavioural and electroencephalographic (EEG) responses similar to those observed with general anaesthetics used clinically. Initial behavioural and EEG excitation, motor incoordination and exaggerated responsiveness to sensory stimuli are followed by a stage of rigid immobility with maintenance of local reflexes (withdrawal, corneal) and EEG arousal in response to stimulation. Finally, there is immobility associated with both EEG and behavioural unresponsiveness to severely noxious stimuli. Such a state of unconsciousness with complete analgesia defines general anaesthesia. This state was completely and rapidly reversed by the specific opiate antagonist, naloxone. The induction of general anaesthesia by a water-soluble neurohormonal peptide acting at specific receptor sites has important implications for traditional theories of anaesthesia.