Changes in the tail surface temperature of the rat following injection of 5-hydroxytryptamine into the ventrolateral medulla.

5-Hydroxytryptamine (5-HT) was injected into the rostral ventrolateral medulla (RVLM) in urethane-anaesthetized rats and its effect assessed on thermoregulatory and non-thermoregulatory cutaneous circulations by the measurement of skin surface temperatures. 5-Hydroxytryptamine (5-50 nmol) produced a dose-related fall in blood pressure (5-20 mmHg) and an increase in tail and plantar foot surface temperatures, indicative of dilatation in the underlying cutaneous circulations. If heat was not applied to the animal, the body temperature fell by 1-2 degrees C within 15-25 min. The decrease in tail and foot temperatures, produced by low frequency (25 Hz, 5 min) electrical stimulation, was antagonized by the injection of 5-HT at the site of stimulation. 5-Carboxyamidotryptamine (2.5-20 nmol) and flesinoxan (5-25 nmol) produced responses similar to 5-HT. The 5-HT2 receptor agonist, alpha-methyl 5-hydroxytryptamine (alpha-methyl 5-HT, 5.5-100 nmol) was only effective in increasing tail and plantar foot temperatures, at dose levels above 25 nmol. However, in a few sites restricted to the anterior region of the RVLM, alpha-methyl 5-HT (11 nmol) evoked a small decrease in tail and foot temperatures, indicative of a constrictor effect, without influencing resting cardiovascular parameters. The results are discussed in relation to the central mechanisms which underly the hypothermia and hyperthermia produced by 5-HT1A and 5-HT2 receptor agonists.

Nonautologous interbody fusion materials in cervical spine surgery: how strong is the evidence to justify their use?

STUDY DESIGN: A review of the literature concerning the use of interbody fusion devices and materials in anterior cervical surgery. OBJECTIVES: To examine the evidence supporting the use of interbody fusion devices as an alternative to autologous bone after anterior cervical discectomy. SUMMARY OF BACKGROUND DATA: Concerns over the morbidity associated with harvesting autologous bone and the risk of transmissible infectious from allografts and xenografts have prompted the search for alternative methods of achieving interbody fusion. Several of these methods have been associated with an unacceptable rate of complications. The clinical and health economic implications of the widespread introduction of interbody fusion devices in the absence of sound evidence cannot be ignored. METHODS: A systematic review of the literature relating to cervical interbody fusion was undertaken. Studies were assessed critically with respect to their methodology, results, and conclusions. RESULTS: Thirty-two clinical studies and 10 laboratory studies were analyzed. Methodologic weaknesses were identified in the majority. Only four clinical reports were either randomized or blinded or involved independent assessment of their outcomes. Fewer than half of the studies included a valid statistical analysis. Radiologic evidence of fusion was limited in many cases. There was little evidence that nonautologous fusion devices offered a reduction in the length of hospital stay. Autologous bone was as effective as, or superior to, many other fusion devices. The early results of some new fusion techniques used alone or in combination showed promise. CONCLUSIONS: There is limited evidence supporting the use of a cervical interbody fusion device in place of autologous bone. There is a need to standardize the testing of implants with good quality laboratory work preceding clinical use. Certain devices including cages, some forms of hydroxyapatite, and bone morphogenic proteins merit further study.

The influence of the ventrolateral medulla on thermoregulatory circulations in the rat.

The rostral ventrolateral medulla (RVLM) was stimulated electrically and chemically (0.1-0.2 microliter, 0.4 M DL-homocysteic acid) in urethane-anaesthetised rats. Changes in the vasomotor tone of the cutaneous circulation of the tail, front and hind feet, the nose and the fur covered areas of the back, proximal hind leg and neck were assessed indirectly by measurement of skin temperatures. Electrical stimulation of the RVLM at 25 Hz (2-5 min) produced sustained decreases in skin temperatures and differed from the effect induced by stimulation at 100 Hz or chemical stimulation, in that the concomitant increases in blood pressure and respiration, as well as the accompanying bradycardia or tachycardia, were minimal and within 10-15% of basal control levels. In the hyperthermic animal changes in the skin temperatures of the tail and feet were observed on stimulation of sites lateral to the rostral third of the inferior olive (IO) and which extended through the nuc. paragigantocellularis lateralis to an area medial to the caudal half of the facial nucleus (FN). There was some degree of topographical organisation with the front and hind feet areas overlying the more extensive tail area in a rostro-caudal orientation. The representation of the other areas of the body was more limited. Neck and nose temperatures changed on stimulation of a small area of the RVLM adjacent to the caudal pole of FN, while the skin of the back and upper hind limb responded to stimulation of a limited area lateral to the rostral pole of IO. The unequal representation of the cutaneous surface probably reflects the degree of vascularisation and the importance of the tail and plantar foot surfaces in thermoregulatory responses.

Metastatic adenocarcinoma masquerading as a solitary nerve sheath tumour.

We present a case of a solitary metastasis of an adenocarcinoma to a dorsal root ganglion (DRG) following a disease free interval of 12 years after resection of a Duke's C carcinoma. The presentation of this unusually placed metastasis was associated with a 3-year complex pain syndrome and radiological appearances consistent with benign disease. The case highlights the importance of not dismissing unusual lesions as innocent in the presence of a history of malignant disease.