Cannabinoid-induced antinociception is mediated by a spinalα2-noradrenergic mechanism

The present study examined whether descending noradrenergic and serotonergic systems mediate the antinociceptive effect of the prototypical cannabinoid, delta-9-tetrahydrocannabinol(Δ⁹-THC). Rats were administered vehicle orΔ⁹-THC (10 mg/kg, i.v.) and subsequently given an intrathecal (i.t.) injection of either theα₂-noradrenergic antagonist, yohimbine, or the non-specific serotonin (5-HT) antagonist, methysergide, through chronically implanted spinal catheters. Whereas yohimbine significantly reversed the cannabinoid-induced elevation of tail-flick latencies, methysergide had no effect. To examine whether yohimbine was indeed blocking the antinociceptive effects ofΔ⁹-THC through a spinal mechanism, it was administered i.t. at either the lumbar or the upper thoracic level of the spinal cord. Antinociception was significantly reduced when yohimbine was administered in the lumbar region; however, administration in the upper thoracic region failed to have an effect. In addition, the effect of i.t. administered yohimbine and methysergide was assessed on two other indices sensitive to cannabinoids, hypothermia and ring immobility. As previously reported, i.v. administration ofΔ⁹-THC led to hypothermia as well as immobility in the ring test which were not blocked by i.t. administration of either monoamine antagonist. To the contrary, methysergide potentiated the hypothermic effect ofΔ⁹-THC. These findings indicate that cannabinoids activate descending noradrenergic neurons resulting in antinociception via the stimulation of spinalα₂-adrenoceptors.     

Ulnar carpal instabilities

Ulnar carpal instabilities are more common than previously suspected. To date, instability patterns have been described at the triquetrolunate and triquetrohamate joints. In this article, the pathomechanics, diagnosis, and treatment of these instability patterns are reviewed and several pertinent case reports are presented.     

Tonic nociception in neonatal rats

The issues of whether infants detect noxious stimuli and whether their nociceptive responses are suppressed by analgesics has been the focus of considerable controversy. Therefore, to more completely assess the nociceptive responses of neonatal rat pups to tonic pain, we tested 3-day-old rat pups using the formalin test. The responses of the young pups to formalin-produced injury were similar to those observed in adult rats, both behaviorally and in terms of their responsivity to morphine-induced antinociception. These results provide the first clear-cut evidence of integrated tonic pain responses in the neonate.     

Lunate silicone replacement arthroplasty in Kienb?ck's disease: a long-term follow-up

We report a long-term follow-up (average, 5 years) of 10 patients who had lunate silicone replacement arthroplasty for treatment of Kienb?ck's disease. Clinical results were assessed on relief of pain, return to normal occupation, and range of motion. At 18- to 20-months follow-up, eight patients had satisfactory results, whereas at final follow-up only five of the patients had satisfactory results. Three of five patients with radiographs averaging 57 months after operation had evidence of particulate synovitis. Contrary to our previous publications on silicone replacement arthroplasty, it was concluded that the success rate for silicone replacement arthroplasty and the incidence of particulate synovitis do not warrant the continued use of silicone replacement arthroplasty as a primary treatment modality for Kienb?ck's disease.