Introduction:
There are two types of phenylalanine, one of the essential amino acids, D-Type and L-type. Phenylalanine in itself has shown no clear analgesic effect in human beings, however, as we reported previously, D-type phenylalanine (DPA) when administered prior to acupuncture analgesia in human beings lengthens the analgesic effects of acupuncture. At this time then, using volunteers in whom acupuncture analgesia failed to raise the pain threshold (PT) we experimentally studied whether or not DPA has any influence.
Methods:
Subjects were divided into an acupuncture anesthesia effective group (a rise in PT was observed due to acupuncture) and an acpuncture anesthesia ineffective group (no rise in PT). 4.0g. DPA was administered orally in both groups 30 minutes prior to acupuncture anesthesia. For acupuncture anesthesia right and left LI-4 and right and left ST-36 were used with low frequency electric current administered for 50 minutes. For the determination of PT a radiant heat pain meter was used. The PT was measured when DPA was administered, during acupuncture anesthesia and at every 30 minutes for 3 hours after the needles were withdrawn.
Results:
In the acupuncture anesthesia effective group, a rise in the PT was observed in 4 of the 5 cases and, the rise was much faster than when acupuncture anesthesia was used alone. In the acupuncture anethesia ineffective group, there were cases in which a remarkable rise in PT was observed or in which no rise in the PT occured during acupuncture stimulation but occured after the discontinuation of the acupuncture and some cases in which no rise occured during or after anesthesia.
Discussion:
1. In the acupuncture anesthesia effective group due to DPA pre-medication, the rate of PT rise quickened.
2. After operations the PT rise was lengthened.
3. The individuality of the acupuncture effectiveness in human beings was partially eliminated.

In this research we conducted a comparative study on the pain threshold elevation resulting from “exercise” work loads, ie. running and cycling, and acupuncture anaesthesia. 10 subjects participated throughout our research; whereas, additional subjects only participated in selected experiments. It was found that the pain threshold increased for both exercise work load and acupuncture anaesthesia; however, no significant correlation was found between the pain threshold elevation percentages resulting from exercise work load and acupuncture anaesthesia.
Therefore we propose, although it has been ascertained that the elevation of pain threshold involves the endomorphin mechanism, that there must be other important mechanisms involved as well.

The term, propagated sensation along the channels (PSC) means the peculiar sensation expeerienced by some people along thier meridians when given acupunctural stimulation of acupoints.
In the present study, the incidence of PSC in outpatients who were undergoing acupuncture treatment was investigated.
Low frequency electrical stimulation was performed through press needles at twenty-six points: the twelve terminal points of the twelve regular meridians and the Inner-Zhiyin points of both sides. PSC was assessed on a four-grade basis after the manner carried out in China.
The incidence of PSC was significantly high among the outpatients compared with that among healthy youth. Patients with hypertension or posttraumatic neck syndrome showed higher incidence of PSC than the other patients.