ENDORPHINERGIC MODULATION OF THE PROCESSE S OF NERVOUS SENSIBILIZATION

Endogenous opioids (EO) effects related to sensory information modulat ion and epileptogenesis are described. Based on the hypothesis of EO p laying this modulator or ''filter'' role, previous experiments in the visual pathway are described in which naloxone (opiate antagonist) pro duced an amplitude increment of the visual evoked potentials (VEP) in the temporal lobe amygdala. The VEP amplitude increment was also obser ved by means of brief low-intensity, repeated electrical stimulation ( kindling procedure) of some limbic and visual structures. Again, this increment was intensified by the administration of naloxone. Previous works related to the effects of opioid antagonist administration alone or during the development of the amygdaloid kindling in encephale iso le preparations and intact free moving cats without anesthesia, are re viewed. In both cases, naloxone facilitated the epileptogenesis. Anoth er sensibilization model documented is the application of the kindling method to the interneuron pathways of the presynaptic inhibition that have properties corresponding to a complex circuitry. The plasticity phenomena becomes evident in the spinal cord trhough the post-tetanic potentiation and habituation processes. We found that the short and re peated stimulation of the aferent cutaneous and muscular nerves produc ed progresively amplitude increase of the polisynaptic reflexes. The p reviously intensified reflexes by the afferent repetitive stimulation were further enhanced by naloxone administration.