A selective effect of naloxone on heterosynaptic C-fibre-mediated inhibitions in the rat dorsal horn.
The effect of naloxone on C-primary afferent-mediated inhibitions of C-fibre-evoked activity in deep dorsal horn neurons has been examined in decerebrate-spinal rats. The same C-afferents that evoke activity in a given neurone can inhibit that C-evoked activity (homosynaptic inhibition), and C-afferent input can also inhibit the activity evoked in dorsal horn neurones by other C-afferents (heterosynaptic inhibition). Naloxone was found to selectively reverse heterosynaptic C-mediated inhibitions without affecting homosynaptic inhibitions. In several neurones the heterosynaptic inhibitions were completely abolished by naloxone. These results show that homo- and heterosynaptic C-mediated inhibitions operate by different mechanisms and that, at least in some neurones, endogenous opioids are likely to be the major inhibitory transmitters involved in producing the heterosynaptic inhibition of the activity evoked by one C-input by another C-input.
D000344:Afferent Pathways / Q000187:drug effects; D000818:Animals; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000187:drug effects; D005727:Ganglia, Spinal / Q000187:drug effects*; D008465:Mechanoreceptors / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology*; D009412:Nerve Fibers / Q000187:drug effects*; D009433:Neural Inhibition / Q000187:drug effects*; D009619:Nociceptors / Q000187:drug effects; D010543:Peroneal Nerve / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013497:Sural Nerve / Q000187:drug effects; D013569:Synapses / Q000187:drug effects*
D009270:Naloxone