Naloxone in ultralow concentration restores endomorphin-1-evoked Ca²⁺ signaling in lipopolysaccharide pretreated astrocytes

Long-term pain is a disabling condition that affects thousands of people. Pain may be sustained for a long time even after the physiological trigger has resolved. Possible mechanisms for this phenomenon include low-grade inflammation in the CNS. Astrocytes respond to inflammatory stimuli and may play an important role as modulators of the inflammatory response in the nervous system. This study aimed first to assess how astrocytes in a primary culture behave when exposed to the endogenous μ-opioid receptor agonist endomorphin-1 (EM-1), in a concentration-dependent manner, concerning intracellular Ca²⁺ responses. EM-1 stimulated the μ-opioid receptor from 10⁻¹⁵ M up to 10⁻⁴ M with increasing intensity, usually reflected as one peak at low concentrations and two peaks at higher concentrations. Naloxone, pertussis toxin (PTX), or the μ-opioid receptor antagonists CTOP did not totally block the EM-1-evoked Ca²⁺ responses. However, a combination of ultralow concentration naloxone (10⁻¹² M) and PTX (100 ng/ml) totally blocked the EM-1-evoked Ca²⁺ responses. This suggests that ultralow (picomolar) concentrations of naloxone should block the μ-opioid receptor coupled G(s) protein, and that PTX should block the μ-opioid receptor coupled G(i/o) protein. The second aim was to investigate exposure of astrocytes with the inflammatory agent lipopolysaccharide (LPS). After 4 h of LPS incubation, the EM-1-evoked Ca²⁺ transients were attenuated, and after 24 h of LPS incubation, the EM-1-evoked Ca²⁺ transients were oscillated. To restore the EM-1-evoked Ca²⁺ transients, naloxone was assessed as a proposed anti-inflammatory substance. In ultralow picomolar concentration, naloxone demonstrated the ability to restore the Ca²⁺ transients.

High intrathecal bupivacaine for severe pain in the head and neck

BACKGROUND

Severe pain in the head and neck is associated with a lowered quality of life and conventional pain therapy often does not provide adequate relief. The aims of this study were to investigate the efficacy, pain relief, benefits and adverse effects of intracisternal or high cervical (IHC) administration of bupivacaine in patients with severe pain in the head, neck and face regions.

METHODS

Between 1990 and 2005, 40 patients (age 27-84 years) were treated with continuous IHC infusions of bupivacaine for various non-cancer (n=15) or cancer-related (n=25) refractory pain conditions (duration 1 month-18 years) in the head, neck, mouth and shoulder regions.

RESULTS

Visual analogue scale scores and opioid requirements decreased markedly after the start of the treatment and remained lowered throughout the study. No tachyphylaxis for bupivacaine was observed. Major side effects were few and most often transient. Most patients showed unchanged or improved mobility. There was no mortality, neurological damage or other severe events attributable to procedures in the study protocol.

CONCLUSION

For patients with severe and refractory pain in areas innervated by cranial and upper cervical nerves, cervical high spinal analgesia can provide safe and effective analgesia.

Comparison of 0.5% intrathecal bupivacaine with 0.5% intrathecal ropivacaine in the treatment of refractory cancer and noncancer pain conditions: results from a prospective, crossover, double-blind, randomized study

BACKGROUND AND OBJECTIVES

Intrathecal (IT) administration of bupivacaine (BUP) for treatment of "refractory" pain has sometimes been associated with unacceptable side effects. This study was undertaken to determine if IT-ropivacaine (ROP) can reduce the rate and intensity of these side effects e.g., urinary retention, paresthesia, and particularly, paresis with gait impairment. A prospective, crossover, double-blind, randomized study.

METHODS

Twenty-one patients were enrolled, 9 dropped out of the study, and data were analyzed from 12 patients. Patients were treated by insertion of IT tunneled nylon catheters, continuous infusion of 0.5% ROP followed by 0.5% BUP or 0.5% BUP followed by 0.5% ROP solutions from an external electronic pump. Each local anesthetic was infused for 7 days, and their order of infusion randomized. The comparative efficacy of the ROP and BUP IT infusions was assessed from the daily doses of IT ROP and IT BUP, oral and parenteral opioids, and daily scores of nonopioid analgetic and sedative drug consumption. Self-reported pain intensity (visual analogue scale [VAS] mean scores) and scores of Bromage relaxation, ambulation, nocturnal sleep pattern, rates of side-effects attributable to the IT drugs, the patients' assessment of the IT ROP v the IT BUP periods of the trial, and the comparative daily cost of IT ROP v IT BUP were recorded.

RESULTS

The daily doses of the local anesthetics used were 23% higher for ROP than for BUP. Further, the daily cost was approximately equals 3 times higher for ROP than for BUP. No other significant differences between IT ROP and IT BUP were found.

CONCLUSION

The results of this study do not support the hypothesis that IT infusion of 0.5% ROP has advantages over IT infusion of 0.5% BUP when administered for relief of "refractory" pain.

Psychopathology in alcohol withdrawal: relationship to alpha2-adrenoceptor function

The possible relationship between postsynaptic alpha2-adrenoceptor function, as assessed by growth hormone (GH) response to clonidine (CLON; 1.5 or 2.0 microg/kg i.v.), and psychopathology was investigated in 30 patients with alcohol-dependence in the early withdrawal period. Excluding patients with high baseline GH, 23 of the 26 patients had blunted GH responses to CLON and 57% moderate or severe depression at day 1 after the end of alcohol intake. After 1 week, the GH responses to CLON remained blunted in 20 of 21 retested patients, whereas the depression and anxiety remitted in all but two patients. The results do not support any relationship between postsynaptic alpha2-adrenoceptor function and symptoms of psychopathology in alcohol withdrawal.

Clinical experience using intrathecal (IT) bupivacaine infusion in three patients with complex regional pain syndrome type I (CRPS-I)

BACKGROUND AND AIM

To date, there is no reliable method for treating the severe pain and for modifying the natural evolution of CRPS-I. Therefore, we explored the effect of long-term IT bupivacaine infusion (with or without buprenorphine) on this syndrome.

PATIENTS AND METHODS

(a)

PATIENTS

two women and one man, 25, 31 and 42 years old, with CRPS-I of the lower (n=2) or upper (n=1) extremity lasting for 4 and 5 months, and 14 years. (b)

INTERVENTIONS

insertion of externalized IT catheters; IT infusion of buprenorphine 0.015 mg/ml and bupivacaine 4.75 mg/ml (n=1), or only bupivacaine 5 mg/ml (n=2) from external electronic pumps.

RESULTS

The IT treatment lasted for 172, 282 and 668 days. The mean/maximal daily doses of the IT bupivacaine were 39/66, 55/80 and 69/125 mg, respectively. The pain intensity decreased from VASmean =7+/-1 to VASmean =2+/-2. None of the patients had regression of allodynia, edema, and trophic disturbances in the affected extremities. In 2 patients, the IT treatment did not prevent spread of the disease to the opposite extremity or the occurrence of phantom pain and stump allodynia after amputation. The IT catheters were withdrawn as being no longer needed: in 2 patients 56 and 458 days after amputation of the involved extremity, and in another one before replacement of the IT bupivacaine infusion with epidural dorsal column stimulation (EDCS). After termination of the IT treatment, the patients were observed for 1437, 1575, and 2689 days (until September 1, 1998). At that date, all the patients were alive, and still affected by their CRPS-I, either in the amputation stump (n=2), and/or in the opposite or remote extremities (n=2); further, two were unemployed and one worked for 75% of the time. One of them was taking up to 1500 mg of slow-release morphine to cope with pain.

CONCLUSION

The IT pain treatment with bupivacaine (with or without buprenorphine) alleviated the "refractory" pain, but affected neither the associated symptoms and signs of the CRPS-I, nor its natural evolution. Thus, the IT treatment cannot be recommended in preference to other pain treatment regimens for CRPS-I.