Studies on the neural mechanism in dorsal root reflex and electroacupuncture

• Main Authors: Lin, Tzer-Bin, 林則彬
• Other Authors: Tsu-Ching Fu
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/41894723751847474332

碩士 === 國立臺灣大學 === 生理學研究所 === 86 === Abstract______________________________________________________Chapter I Investigations on Dorsal Root Reflex : Under normal conditions, sensory i nformation enters central nervous system through dorsal roots (DRs), while mot or activity emerges via ventral roots (VRs). However, under certain conditions activity can be detected emerging antidromically towards periphery in the DR fibers as dorsal root antidromic discharge (DRAD) or dorsal root reflex (DRR). The purposes of this study are as follows: 1) to explore the characteristic s of the DRR.2) to determine which fibers are responsible for activating and t ransmitting the DRR.3) to clarify the neuronal pathways involved.4) to elucida te possible physiological function of the DRR. The recorded DRR in single fi bers, teased down from the severed L5 dorsal root central stump, initiated spo ntaneously or induced by stimulation (St) of sciatic nerve (SN), was studied i n anesthetized rats. The results are summarized as in the following:1. The e xcitation of group II afferents were the major inputs to induce DRRs which wer e transmitted mainly in fibers with conduction velocity below 20 m/s, and its central delay was 3-5 ms. 2. The firing frequency of both spontaneous and ipsi laterally induced DRRs were increased 2-4 times after spinalization.3. When th e time interval between two subthreshold stimuli was less than 4.8 ms, DRR was activated. However, when the time interval between two suprathreshold stimuli was kept between 5-20 ms, the second DRR was abolished.4. The DRR was also el icited by contralateral SN St but was abolished by spinalization, and its cent ral delay was 24-30 ms; the contralaterally induced DRR also showed the phenom ena of temporal and spatial facilitation and inhibition.5. When the time inter val between the stimuli to ipsilateral and to contralateral SNs St was 6-15 ms, the second DRR was always blocked by the first one and vice versa. In o rder to test whether the DRR plays any possible role in the physiological func tion, the reactivity of muscle spindles in gastrocnemius-soleus (GS) muscles f ollowing DR antidromic stimulation (ASt) was investigated in anesthetized rats . The results are summarized as in the following:1. In response to ASt, two different types of endings were found: type I, its tonic discharge was not al tered following ASt at 100 Hz for 10 sec, while type II was significantly inhi bited even at a frequency of 50 Hz. 2. At 300 Hz, both types of endings were i nhibited, however, type I recovered in less than 4 sec, while type II took mor e than 15 sec to return to control level; and a silent period (1-5 sec) was fo und in type II but not in type I. 3. The effective minimum inhibitory frequenc y for type I and type II was 200 and 50 Hz respectively. From all the findi ngs stated above, we suggest that DRR may play an important role in the modula tion of sensory afferent input regulated by supraspinal structures.Chapter II Investigations on Electroacupuncture Effects The following work was designed to investigate the neural mechanism of electroacupuncture (EA). Two sets of experiments were carried out to determine the effect of EA on circulat ory, urinary and the nervous systems. Response of arterial blood pressure (B P) and adrenal nerve activity (ANA) to EA were studied in anesthetized rats an d the results are summarized as following:1. At Tsusanli, EA was of no effect. However, at Hoku, an elevation of BP and ANA was elicited during EA when the intensity was 5xT or higher. 2. The pattern of pressor effects caused by EAs w ith frequency of 3 and 30 Hz were different, i.e., a tonic effect was elicited with frequency of 3 Hz, while a phasic one was induced with 30 Hz. 3. The pre ssor effects elicited by bilateral EAs were similar to that of unilateral ones , except the latency to reach the maximal effect was shortened. 4. A combinati on of both phasic and tonic effects on BP and ANA was obtained when EA at Hoku on both sides simultaneously with different frequencies (3 and 30 Hz) on each side. 5. The pressor effects elicited by EA was not affected by adrenalectomy , but abolished by regitine, an alpha adrenergic blocker. To address the ef fect of EA on bladder activity, responses of rhythmic micturition contraction (RMC), urine excretion (UE), BP, sympathetic renal nerve activity (RNA) and pe lvic parasympathetic nerve activity (PNA) elicited by EA were investigated in urethane-anesthetized rats. The results are summarized as following:1. Elon gation of RMC cycle and increase in UE associated with the elevation of BP and RNA were elicited during EA at Hoku. 2. The pressor response induced by low f requency EA (LFEA) was different from that by high frequency EA (HFEA), i.e., a tonic effect was elicited by LFEA, while a phasic one was induced by HFEA. These results implicate that (1) EA at Hoku with different stimulation frequ ency may excite a distinct mechanism to activate the sympathetic nervous syste m, (2) EA with stimulation intensity of 5xT or higher can increase and maintai n BP 、ANA and RNA as well as elongate RMC. (4) EA at Hoku may elevate BP and ameliorate the hyperactive bladder in clinical therapy.