A correlation analysis of the regional distribution of central enkephalin and β‐endorphin immunoreactive terminals and of opiate receptors in adult and old male rats. Evidence for the existence of two main types of communication in the central nervous system: the volume transmission and the wiring transmission

Abstract

By means of semiquantitative immunocytochemistry and quantitative receptor autoradiography a correlation analysis has been performed on the pre- and post-synaptic features of enkephalin and beta-endorphin immunoreactive neuron systems of the 3- and 24-month-old male rat. A parallel disappearance of enkephalin- and beta-endorphin-like immunoreactivity and of the density of mu and delta opiate receptors is shown during ageing. Furthermore, the lack of an overall correlation between the amount of pre- and post-synaptic components of the enkephalin and beta-endorphin synapses give evidence for the existence of a volume type of transmission in such systems in the telencephalic, diencephalic and mesencephalic areas analysed.