L-Arginine/nitric oxide pathway in chronic tension-type headache: relation with serotonin content and secretion and glutamate content.

Previous research of our group demonstrated an increase in L-arginine/nitric oxide (NO) pathway activity in patients with chronic daily headache (CDH) with a previous history of migraine, which was associated with a reduced platelet serotonin content and increased Ca(2+) levels. In the present work, we assessed the variations in L-arginine/NO pathway activity and platelet cyclic guanosine 3',5'-monophosphate (cGMP) levels in 25 patients affected by chronic tension-type headache (CTTH) (8 M, 17 F; age range: 34-54 years). The NO production, shown spectrophotometrically by stoichiometric transformation of oxyhemoglobin to methemoglobin due to NO synthase (NOS) activity, and inter platelet cGMP concentration, assessed with a RIA method, were determined in parallel to variations of aggregation response to 0.3 microg/ml collagen. The intracellular platelet calcium concentrations were also determined using fluorescence polarisation spectrometry. Platelet serotonin content and collagen-induced secretion as well as glutamate content were also determined with high-performance liquid chromatography (HPLC). The above parameters were compared with those of an age-matched control group. A reduction in aggregation platelet response was found. The reduction in platelet aggregation was coupled with an increased NO and cGMP production (p<0.0002 and p<0.001, respectively). A significant increase in cytosolic Ca(2+) concentration was also detected compared to control individuals (p<0.001). This was accompanied by a reduced platelet content and collagen-induced secretion of serotonin and increased content of glutamate (p<0.0001, p<0.0001 and p<0.001, respectively). The above findings were more evident in patients with analgesic abuse. It can be hypothesized that the increased NOS activity shown in platelets of CTTH patients reflects an analogous central up-regulation of NOS activity in the spinal horn/trigeminal nucleus and supraspinal structures involved in the modulation of nociceptive input from myofascial cranial structures contributing to central sensitization. The increase in NOS activity seems to be associated with a hyposerotonergic status, particularly in patients with analgesic abuse, and this can contribute to central sensitization in CTTH patients. The increase in platelet glutamate content in the same patients suggests the implication of the above excitatory amino acid in spinal and supraspinal structures involved in head pain induction and maintenance.