The present paper is divided into two parts.The nucleus caudatus has been described briefly in the first part.(1) The nervous circuity ofnucleus eaudatus:The pars compacta of substantia nigra contains the cell body of one of the maindopamine(DA) fiber systems

the nigro-striatal pathway

which comes from substantia nigra and goesto the nucleus caudatus.There is a neo-striato-nigra pathway

too

making it possible for caudatumand substantia nigra to influence each other's activity.(2) The link of neurons in caudatum:It has been proposed that in the pathway there is a cholinergic link through which caudate DAterminals influence GABA neruronal activity both in interneurons in caudatus and in descendingGABAergic pathways to the substantia nigra.The inhibitory nervous feedback control of the nigro-striatal DA pathway thus seems to involve the inactivation of cholinergic interneurons in thecaudatus

allowing an increased activity to occur in descending inhibitory GABAergic pathwaysinnervating the DA nerve cells of the substantia nigra.(3) The characteristics of dopamine receptors:The theory of excitation-mediating and inhibition-mediating dopamine receptors has beenintroduced.The histochemical

biological

electrophysiological

pharmacological and functionalcharacteristics of dopaminergic receptors have also been described.It is proposed that the excitation-mediating receptors might be situated before

and the inhibition-mediating receptors

after thesynapses.The second part deals with the relationship between the nucleus caudatus and acupuncture anal-gesia.The experiments suggest that the nucleus caudatus has a powerful action to elevate the painthreshold and strengthen the analgesia effect of acupuncture.But the mechanism of oaudate analgesiais not clear yet.Some studies suggest that the dopaminergic system in the nucleus caudatus has anopposite effect on acupuncture analgesia.