Motoneuron excitability: the importance of neuromodulatory inputs

The excitability of spinal motoneurons is both fundamental for motor behavior and essential in diagnosis of neural disorders. There are two mechanisms for altering this excitability. The classic mechanism is mediated by synaptic inputs that depolarize or hyperpolarize motoneurons by generating postsynaptic potentials. This "ionotropic" mechanism works via neurotransmitters that open ion channels in the cell membrane. In the second mechanism, neurotransmitters bind to receptors that activate intracellular signaling pathways. These pathways modulate the properties of the voltage-sensitive channels that determine the intrinsic input-output properties of motoneurons. This "neuromodulatory" mechanism usually does not directly activate motoneurons but instead dramatically alters the neuron's response to ionotropic inputs. We present extensive evidence that neuromodulatory inputs exert a much more powerful effect on motoneuron excitability than ionotropic inputs. The most potent neuromodulators are probably serotonin and norepinephrine, which are released by axons originating in the brainstem and can increase motoneuron excitability fivefold or more. Thus, the standard tests of motoneuron excitability (H-reflexes, tendon taps, tendon vibration and stretch reflexes) are strongly influenced by the level of neuromodulatory input to motoneurons. This insight is likely to be profoundly important for clinical diagnosis and treatment.

A randomized experiment of the effects of including alternative medicine in the mandatory benefit package of health insurance funds in Switzerland

OBJECTIVES

The present investigation focuses on the following questions: 1. Are complementary medical services paid for by a health insurer used in addition to orthodox medical services, or as substitute for them?; 2. If health insurers include complementary medical services in the basic cover, what will be the effect on costs?; 3. If complementary medical services as included in the basic cover, what will be the effect on the policyholders' subjective state of health?

STUDY DESIGN

A randomized experiment was set up in which 7500 members of Switzerland's biggest health insurance fund, Helvetia, were offered free supplementary insurance for alternative medicine for 3 years. This simulated a situation in which the experimental group had access to the full range of complementary medical treatments under their health insurance policies. The remaining members in the scheme (670,000) people) formed the control group. To evaluate the effect on costs, we analysed the health insurer's cost and benefits data. In addition, a survey was carried out among random samples of subjects from the experimental group and from the control group using the 36-Item Short-Form Health Survey (SF-36) to examine the effects of including complementary medicine on subjective state of health.

RESULTS

The analysis of the cost data shown that subjects used alternative in addition to orthodox medical services. It is also clear that alternative medical treatments are given in combination with orthodox medicine; less than 1% of the experimental group used exclusively alternative medical services. However, as only a very small percentage of experimental subjects (6.6%) took advantage of complementary medicine, no significant impact on overall health costs can be inferred. On the other hand, multiple regressions show that use of complementary medicine has a greater effect on treatment costs than sex, age or language region. Neither at the beginning nor the end of the experiment were any significant differences noted in the scales of the SF-36 between the experimental and the control group. Nor did multiple regressions reveal any effects on subjects' state of health due to the inclusion of complementary medicine in the basic insurance cover.

[Transanal endoscopic microsurgery]

A new endoscopic surgical method was developed for removal of large sessile adenomas of the rectum and lower sigmoid. Stereoscopic sight and magnifying glasses do allow precise surgery of these tumors. If adenomas are present they can be removed using the technique of mucosa excision; if on the other hand rectum carcinomas have to be removed the complete wall of the rectum in an appropriate extension can be excised. Hemorrhages which occur during preparation always can be stopped by diathermy. The surgical intervention is terminated by a transverse continuous suture of the defect. 33 patients were operated upon in this way from July 1983 to April 1985. Areas with an diameter of up to 10 cm could be removed, even located up to 18 cm in the colon. Suturing of the defect could always be performed without problem. In 1 patient a relapse occurred.

Endoscopic surgery in the rectum

A new transanal endoscopic operative technique permits microsurgery in the rectal cavity and the placing of surgical sutures. Compared with other procedures this one is non-aggressive, and there were not postoperative complications in twelve cases. A stereoscopic optical system, a new operating rectoscope and special surgical instruments, as well as a modification to an insufflation device are necessary for the endoscopic operation.

[Transanal endoscopic surgery of the rectum - testing a new method in animal experiments]

Surgery of the lower third of the rectum can be done without difficulty through the anus using an endoscopical approach. Polyps or tumors located in the upper two thirds of the rectum can be removed using the Mason or Kraske procedure, or by the transabdominal approach. A new endoscopic technique has been developed with the aim, to allow surgery in the whole rectum through the anus. The rectum is being dilated by mechanical means and air insufflation. An oblique angle stereoscopic endoscope as well as modified surgical instruments are used. In animals 47 excisions of mucosa were done, and the incisions were closed by continuous suture. Application of this technique in a clinical setting is planned.

[Outcome of sphincter-preserving stapled colorectal anastomoses]

Anterior colorectal end-to-end anastomosis by stapler was achieved in 61 patients between 1979 and 1981. The clinical occurrence of anastomotic leakage was 8,2%. The main advantage of the stapler is in anastomosis low in the pelvis where it allows easier access to the extraperitoneal part of the rectum. In patients with colorectal carcinoma in the middle part of the rectum the number of abdomino-perineal excisions decreased from 10,2% in 1979/80 to 3% in 1981. Recurrence of carcinoma took place in three cases after radical resection of rectosigmoidal tumor. Therefore repeated follow-up examinations with endoscopy in these cases are imperative.

[Idiopathic megacolon (author's transl)]

The diagnosis of congenital megacolon can only rarely be established in adult cases with dilatation of the rectum and sigma, since the narrow aganglionic segment and increased levels of plasma acetylcholinesterase activity are usually lacking in adult cases,--these findings being typical for congenital megacolon. Idiopathic megacolon thus is the correct diagnosis in most of these adult cases. Surgical removal of the dilated parts of the intestine and end-to-end anastomosis yield satisfactory results, thus a colostomy is not necessary.