SYNAPTIC CONNECTIONS BETWEEN ENDOMORPHIN-IMMUNOREACTIVE TERMINALS AND ? OPIOID RECEPTOR-IMMUNOREACTIVE NEURONS IN THE SPINAL DORSAL HORN OF THE RAT / 解剖学报

ABSTRACT

Objective To investigate the synaptic connections between endomorphin-immunoreactive(ir) terminals and ? opioid receptor-ir neurons in the superficial layers(laminae Ⅰ and Ⅱ) of the rat spinal dorsal horn. Methods The double-labeling immunohistochemical electron microscopic technique,i.e.pre-embedding immunohistochemical detection of endomorphin combin with pre-embedding immuno-gold particles labeling technique to identify ? opioid receptor-immunoreactivity,was used in the present study. Results ? opioid receptor-ir neuronal cell bodies,fibers as well as axon terminals were observed in laminae Ⅰ and Ⅱ of the spinal dorsal horn,meanwhile dense endomorphin-ir axon terminals were located mainly within the same region.Under electron microscope,the synaptic connections formed by endomorphin-ir axon terminals labeled with diaminobenzidine(DAB) reaction products and ? opioid receptor-ir neuronal cell bodies and dendritic profiles labeled with immuno-gold particles were observed.The principle synaptic type was asymmetric synapse.There were more axon-dendritic synapses than axon-somatic ones as encountered in the present study.Conclusion The distribution patterns of endomorphin-ir and ? opioid receptor-ir structures match with each other in the superficial laminae of the spinal dorsal horn,that provides morphological base for the antinociceptive effects of endomorphin and ? opioid receptor in the processing of nociceptive information transmission.