Role of the thalamic parafascicular nucleus cholinergic system in the modulation of acute corneal nociception in rats

The present study investigated the effects of microinjections of acetylcholine (a cholinergic agonist), physostigmine (a cholinesterase inhibitor), atropine (an antagonist of muscarinic cholinergic receptors) and hexamethonium (an antagonist of nicotinic cholinergic receptors) into the parafascicular nucleus of thalamus on the acute corneal nociception in rats. Acute corneal nociception was induced by putting a drop of 5 M NaCl solution onto the corneal surface of the eye and the number of eye wipes was counted during the first 30s. Both acetylcholine and physostigmine at the same doses of 0.5, 1 and 2 μg significantly (P < 0.05) reduced the number of eye wipes. The intensity of corneal nociception was not changed when atropine and hexamethonium were used alone. Atropine (4 μg), but not hexamethonium (4 μg) significantly (P < 0.05) prevented acetylcholine (2 μg)- and physostigmine (2 μg)-induced antinociceptive effects. The results indicated that at the level of the parafascicular nucleus of thalamus, the muscarinic cholinergic receptors might be involved in the antinociceptive effects of acetylcholine and physostigmine

Effects of Histidine and Dexamethasone on the Local Inflammation Induced by Histamine in Rats

In this study, the effects of separate and combined intraperitoneal (IP) injections of histidine and dexamethasone were investigated on local inflammation in rats. Local inflammation was induced by subcutaneous (SC) injection of histamine (100 μl, 0.1%) in ventral surface of right hind paw. The thickness of paw was measured at 30 min before and 30, 60, 90, 120, 150 and 180 min after injection of histamine, using a fine caliper. The number of neutrophils in paw tissue sections was counted 3 h after intraplantar (IPL) injection of histamine. The IPL injected histamine elicited an inflammatory response that was characterized by increase of paw thickness and by infiltration of neutrophils in paw tissues. IP injections of histidine at doses of 200 and 400 mg kg-1 and dexamethasone at a dose of 1 mg kg-1 significantly (P < 0.05) decreased both paw thickness and infiltration of neutrophils in paw tissues. In combined treatment, IP injection of histidine (200 mg kg-1) with dexamethasone (1 mg kg-1) produced a more documented response in comparison with histidine and dexamethasone used alone. The results suggested that histidine and dexamethasone have anti-inflammatory activities. Histidine potentiated the anti-inflammatory effect of dexamethasone in histamine-induced local inflammation

Histological and histometrical studies on the Effects of Fluoride on the Femur in Rats

Background: Fluoride (F&minus) is a trace element that is incorporated into bone mineral during bone formation. This study assessed the effect of increasing Fluoride doses on the bone formation and microarchitecture on the Femur of rats by histological, and histometrical methods. Materials and Methods: A total of 16 rats was divided into one group of control and three groups of animals that received 0.2, 0.4, 0.8 mg/kg of Fluoride daily for 3 weeks by gavage. Rats which were exposed to inorganic Fluoride in drinking water produced significantly more levels of bone lesions than the controls. Results: Numerous osteocyte lacunae buried at various depths were evident, and the lacunar walls were irregular with mineralized segments running in all directions. The trabeculae of cancellous bone in these animals contained large amounts of osteoid. Conclusion: The results of the present study indicated that the ingestion of Fluoride affected morphological changes in the Femur of rats