Effect of norepinephrine on spinal cord blood flow and parenchymal hemorrhage size in acute-phase experimental spinal cord injury.

International audiencePURPOSE: In the acute phase of spinal cord injury (SCI), ischemia and parenchymal hemorrhage are believed to worsen the primary lesions induced by mechanical trauma. To minimize ischemia, keeping the mean arterial blood pressure above 85 mmHg for at least 1 week is recommended, and norepinephrine is frequently administered to achieve this goal. However, no experimental study has assessed the effect of norepinephrine on spinal cord blood flow (SCBF) and parenchymal hemorrhage size. We have assessed the effect of norepinephrine on SCBF and parenchymal hemorrhage size within the first hour after experimental SCI. METHODS: A total of 38 animals were included in four groups according to whether SCI was induced and norepinephrine injected. SCI was induced at level Th10 by dropping a 10-g weight from a height of 10 cm. Each experiment lasted 60 min. Norepinephrine was started 15 min after the trauma. SCBF was measured in the ischemic penumbra zone surrounding the trauma epicenter using contrast-enhanced ultrasonography. Hemorrhage size was measured repeatedly on parasagittal B-mode ultrasonography slices. RESULTS: SCI was associated with significant decreases in SCBF (P = 0.0002). Norepinephrine infusion did not significantly modify SCBF. Parenchymal hemorrhage size was significantly greater in the animals given norepinephrine (P = 0.0002). CONCLUSION: In the rat, after a severe SCI at the Th10 level, injection of norepinephrine 15 min after SCI does not modify SCBF and increases the size of the parenchymal hemorrhage

Rat model of spinal cord injury preserving dura mater integrity and allowing measurements of cerebrospinal fluid pressure and spinal cord blood flow.

International audiencePURPOSES: Cerebrospinal fluid (CSF) pressure elevation may worsen spinal cord ischaemia after spinal cord injury (SCI). We developed a rat model to investigate relationships between CSF pressure and spinal cord blood flow (SCBF). METHODS: Male Wistar rats had SCI induced at Th10 (n = 7) or a sham operation (n = 10). SCBF was measured using laser-Doppler and CSF pressure via a sacral catheter. Dural integrity was assessed using subdural methylene-blue injection (n = 5) and myelography (n = 5). RESULTS: The SCI group had significantly lower SCBF (p < 0.0001) and higher CSF pressure (p < 0.0001) values compared to the sham-operated group. Sixty minutes after SCI or sham operation, CSF pressure was 8.6 ± 0.4 mmHg in the SCI group versus 5.5 ± 0.5 mmHg in the sham-operated group. No dural tears were found after SCI. CONCLUSION: Our rat model allows SCBF and CSF pressure measurements after induced SCI. After SCI, CSF pressure significantly increases

Effects of Adenosine Monophosphate Used in Combination with L‐Arginine on Female Rabbit Corpus Cavernosum Tissue

Introduction: Sexual dysfunction is significantly more prevalent in women than in men. However, to date, no satisfactory oral treatment is yet available. Aim: The aim of this study was to study the effects of adenosine monophosphate (AMP) alone or its combination with L‐Arginine on the relaxation of the female rabbit corpus cavernosum. Methods: Cylinder strips from the corporal body of the excised clitoris from female New Zealand White rabbits were incubated in Krebs solution. Phenylephrine (PE) precontraction was achieved, then the drugs AMP and L‐Arginine were administered either independently or in sequential combinations to the strips under precontracted conditions. Main Outcome Measures: Contraction percentages were compared. Results: When precontraction was induced by PE 8 μM or 20 μM, AMP was shown to induce relaxation up to 25% in a dose‐dependent manner. The relaxation induced by L‐Arginine reached 15.6% at 5.10−4 M vs. 16.5% at AMP 5.10−4 M under the same experimental conditions. Nitric oxide (NO) synthase inhibitor N‐nitro‐L‐arginine strongly inhibited the relaxing effect provoked by AMP, suggesting that the action mechanism of this nucleotide is related to the NO pathway. The combination of L‐Arginine at 5.10−4 M with AMP at different doses ranging from 5.10−4 M to 10−3 M significantly amplified the relaxing response up to 40.7% and 58%, respectively. Conclusions: Our results demonstrate that AMP induces a relaxing effect on the female rabbit corpora. They also show that L‐Arginine and AMP can potentiate each other and that a synergistic effect can be obtained by their combined use. Because only slight differences exist between both sexes in response to NO donors and/or nucleotide purines or in their use together, it is very likely that close biochemical mechanisms, although not to the same degree and not quite similar, are involved in the engorgement of the penis and the clitoris of New Zealand White rabbits. Stücker O, Pons C, Neuzillet Y, Laemmel E, and Lebret T. Original research‐sexual medicine: Effects of adenosine monophosphate used in combination with L‐Arginine on female rabbit corpus cavernosum tissue. Sex Med 2014;2:1–7