Effect of intrathecally administered local anesthetics on protein phosphorylation in the spinal cord

Lidocaine prevents referred hyperalgesia associated with cystitis

AIMS

Lidocaine produces analgesia by inhibiting excitation of nerve endings or blocking impulse conduction in peripheral nerves. This study was performed to determine whether intrathecal or intravesical administration of lidocaine prior, or subsequent, to induction of chemical cystitis in rats would block referred mechanical hyperalgesia.

METHODS

Intrathecal or intravesical lidocaine was administered 15 (intrathecal) or 30 (intravesical) min before intravesical instillation of saline or 1 mM acrolein (400 microl) or 4 hr after saline or acrolein instillation in female Wistar rats. Mechanical sensitivity of hind paws was determined at 24 hr prior to any treatment (baseline) and, 4, 24, and 48 hr after intravesical instillation of acrolein or saline. Also, nerve growth factor (NGF) content was measured in bladder and dorsal root ganglia (DRG).

RESULTS

Pre-treatment with intrathecal or intravesical lidocaine attenuated acrolein-induced referred mechanical hyperalgesia of the hind paws. Lidocaine administered after acrolein instillation did not alter referred hyperalgesia. Lidocaine treatment prior to or after induction of cystitis reduced NGF content in the bladder.

CONCLUSIONS

These results indicate that pre-treatment with lidocaine attenuates referred hyperalgesia associated with cystitis. Lidocaine treatment 4 hr after induction of cystitis failed to prevent referred hyperalgesia despite a similar decrease in bladder NGF. Neurourol. Urodynam. (c) 2009 Wiley-Liss, Inc.

AMP-activated protein kinase activity during metabolic rate depression in the hypoxic goldfish, Carassius auratus

Cell survival during hypoxia exposure requires a metabolic reorganization to decrease ATP demands to match the reduced capacity for ATP production. We investigated whether AMP-activated protein kinase (AMPK) activity responds to 12 h exposure to severe hypoxia ( approximately 0.3 mg O2 l(-1)) in the anoxia-tolerant goldfish (Carassius auratus). Hypoxia exposure in goldfish was characterized by a strong activation of creatine phosphate hydrolysis and glycolysis in liver and muscle. AMPK activity increased by approximately 5.5-fold in goldfish liver within 0.5 h hypoxia exposure and this increase in activity was temporally associated with an 11-fold increase in [AMP(free)]/[ATP]. No changes in total AMPK protein amount were observed, suggesting that the changes in AMPK activity are due to post-translational phosphorylation of the protein. Hypoxia exposure had no effect on the expression of two identified AMPK alpha-subunit isoforms and caused an approximately 50% decrease in the mRNA levels of AMPK beta-subunit isoform. Changes in AMPK activity in the liver were associated with an increase in percentage phosphorylation of a well-characterized target of AMPK, eukaryotic elongation factor-2 (eEF2), and decreases in protein synthesis rates measured in liver cell-free extracts. No activation of AMPK was observed in muscle, brain, heart or gill during the 12 h hypoxia exposure suggesting a tissue-specific regulation of AMPK possibly related to a lack of change in cellular [AMP(free)]/[ATP] as observed in muscle.