For the purpose of providing further morphological evidences to explain the gate control theory of pain mechanism the electron microseope-immunocyto- chemistry of a few structures relating to pain were studied.After unilateral transection of the dorsal roots(L1-5)of rat spinal cord

the animals were perfused through heart with 4% paraldehyde and the vibratome sections of corresponding segments of cord were treated by Sternberger's PAP technique or HRP protein A(HRP-PA)method for the demonstration of SP-and ENK- immunoreactivity(IR).Then the positive region of immunoreaction in laminae Ⅰ

Ⅱ was removed and further processed for electron microscopic observations. It was found: 1)SP-IR was present in the central nerve ending of synaptic glomerule withwhich the unlabelled dendrites and axons were synapsed to form axo(SP)- dendritic(unlabelled)axo(SP)-axonic(unlabelled)

and dendro(unlabelled)- axonic(SP)contacts.These patterns of synapse may interpret that the nociceptive information transmitted via the SP containing central ending of glomerule might be transfered to many dendrites of neurons in deeper layers and would be modulated by the presynaptie dentrite. 2)The triad synaptie pattern

ie:axo(SP or ENK)-dendrite(unlabeled)- axonic(SP or ENK)might represent that different informations via different SP or ENK containing axons may converge to a common dentrite. 3)The presence of axo(ENK)-axonic(degenerated)synapse after transe- ction of dorsal roots would be regarded as the one of the important neuroan- atomic basis for the ENK presynaptic inhibition of the SP containing afferent nerve.Thus

anyway

the existance of presynaptic inhibition at the level of substantia gelatinosa could not be excluded. 4)The synapse of double ENK containing processes was also found. Because a lot of“interneuron and SG cell”as illustrated in the diagram of Melzack-Wall's gate theory were proved to be ENKnergic

the figure of axo (ENK)-axonic(ENK)synapse found in present paper might be considered as a morphological evidence of de-inhibitlon function in superficial layers of dorsal horn.