Renin-angiotensin system blockade modulates both the peripheral and central components of neuropathic pain in rats: Role of calcitonin gene-related peptide, substance P and nitric oxide

Nonetheless, renin-angiotensin-aldosterone system (RAAS) blockers attenuate neuropathic pain (NP), the exact molecular mechanisms of this effect are not completely understood. The study aimed to investigate the role of calcitonin gene-related peptide (CGRP), substance P (SP) and nitric oxide (NO), which are all involved in pain modulation, in the analgesic effect of different RAAS blockers in NP both on the peripheral and on the central levels. NP was induced by sciatic nerve chronic constriction injury (CCI, 14 days) in rats, that were given either centrally (telmisartan and ramipril) or peripherally (losartan and enalapril) acting angiotensin-converting enzyme inhibitors (ACE-Is) or angiotensin receptor blockers (ARBs). Behavioural assessment was performed, and CGRP, SP and NO levels were detected in the injured sciatic nerve and the brainstem at the end of experiment. CCI rats showed increased spontaneous pain response and foot deformity along with elevated CGRP, SP and NO levels. ARBs and ACE-Is treatment improved pain behaviour and reduced SP and NO levels. However, sciatic CGRP was increased with different interventions and brainstem CGRP was only elevated in the losartan group. These findings suggest an intermediary role of CGRP, SP and NO in RAAS blockers analgesic effect in NP.

Mechanisms Involved in Superiority of Angiotensin Receptor Blockade over ACE Inhibition in Attenuating Neuropathic Pain Induced in Rats

Although previous reports described the beneficial role of angiotensin-converting enzyme inhibitors (ACE-Is) or AT1 receptor blockers (ARBs) in attenuating neuropathic pain (NP), no study has yet explored the exact underlying mechanisms, as well as the superiority of using centrally versus peripherally acting renin-angiotensin-aldosterone system (RAAS) drugs in NP. We investigated the effects of 14 days of treatment with centrally (telmisartan and ramipril) or peripherally (losartan and enalapril) acting ARBs and ACE-Is, respectively, in attenuating peripheral NP induced by sciatic nerve chronic constriction injury (CCI) in rats. We also compared these with the effects of pregabalin, the standard treatment for NP. Behavioral changes, inflammatory markers (NFкB, TNF-α, COX-2, PGE2, and bradykinin), oxidative stress markers (NADPH oxidase and catalase), STAT3 activation, levels of phosphorylated P38-MAPK, ACE, AT1 receptor (AT1R), and AT2 receptor (AT2R), as well as histopathological features, were assessed in the brainstem and sciatic nerve. CCI resulted in clear pain-related behavior along with increased levels of inflammatory and oxidative stress markers, and STAT3 activity, as well as increased levels of phosphorylated P38-MAPK, ACE, AT1R, and AT2R, along with worsened histopathological findings in both the brainstem and sciatic nerve. ARBs improved both animal behavior and all measured parameters in CCI rats and were more effective than ACE-Is. At the tested doses, centrally acting ARBs or ACE-Is were not superior to the peripherally acting drugs of the same category. These findings suggest that ARBs (centrally or peripherally acting) are an effective treatment modality for NP.

Microencapsulation of ketorolac tromethamine by means of a coacervation-phase separation technique induced by the addition of non-solvent

Ketorolac tromethamine (KT) is a non-steroidal drug with potent analgesic and anti-inflammatory activity and is absorbed rapidly (Tmax < 1.0 h) with an efficiency > 87% following oral and intramuscular administration. The plasma half-life of ketorolac ranges from 1.1 to 6.0 h. Its oral bioavailability is estimated to be 80%. Ketorolac has been found 36 times more potent than phenylbutazone, approximately twice as potent as indomethacin, and three times more potent than naproxen in suppressing carrageenan-induced paw oedema in rat. In this study, microcapsules of KT were prepared by means of coacervation-phase separation technique induced by the addition of non-solvent, and release rates from microcapsules were studied. Eudragit S100 was used as the coating material. Coacervation was achieved by the addition of cyclohexane at 2 ml/min at 25 degrees C and 1:4 solvent: non-solvent ratio was used. The microcapsules were washed with cyclohexane to harden the wall and dried at room temperature. Microcapsules with core:wall ratio of 1:1 and 1:2 were prepared and the particles obtained by sieving with an average diameter of 177-500 microns were used. The yield was calculated and the release properties of KT were investigated by USP XXII paddle method and using UV spectrophotometry at 318 and 323 nm.

Laboratory study of trachoma in Egyptian rural schoolchildren

Cytological preparations from the conjunctiva of schoolchildren were examined by Giemsa staining and by an indirect fluorescent antibody (FA) technique. In addition, chlamydial group-specific antibodies in sera were measured with the complement fixation (CF) test. It has consistently been shown that the FA technique is more sensitive than Giemsa staining for the cytological demonstration of intracytoplasmic inclusions in conjunctival cells from trachoma patients, but reports differ regarding the degree of its superiority. The present study confirmed that the FA technique is more sensitive. Furthermore, the demonstration of intracytoplasmic inclusions by the FA technique correlated to a high degree with the intensity of the clinical signs of trachoma. With chlamydial (bedsonial) group antigen, the CF test yielded positive results in only a small proportion of cases. However, in areas where the disease is hyperendemic, a standardized CF test may show a correlation of positive results with the intensity of clinical signs. This is the case in the present study when low CF titres are considered as positive. The CF test may thus provide useful laboratory support for comparative studies of trachoma in large population groups.