| Summary: | 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.
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