Changes in vascular alpha1‐ and alpha2‐adrenoceptor responsiveness by selegiline treatment

Abstract

Pharmacoepidemiological studies have reported an excess of mortality with selegiline, a MAO B inhibitor used in the treatment of Parkinson's disease. The mechanism of this putative adverse effect remains unknown but an interaction with the sympathetic nervous system was suggested. The aim of the present study was to investigate the influence of selegiline (10 mg/daily, orally during one week) on vascular alpha1- and alpha2-adrenoceptor responsiveness in conscious unrestrained dogs. Selegiline significantly increased resting values of both systolic and diastolic blood pressures and noradrenaline plasma levels (HPLC) without changing heart rate. Moreover, spectral analysis of systolic blood pressure (Fast Fourier Transformation) showed that selegiline increased the relative energy of a low frequency band without modifying the total spectrum. ED 50 calculated from dose-pressor response curves with phenylephrine (after beta-blockade by propranolol), an index of alpha1-adrenoceptor response or with noradrenaline (after alpha1- and beta blockade by prazosin plus propranolol), an index of alpha2-adrenoceptor response, were significantly higher after selegiline. Selegiline failed to modify the number of platelet alpha2-adrenoceptors measured by [(3)H] RX 821002 binding. Yohimbine-induced increase in noradrenaline release was significantly more marked after selegiline. These results support the evidence that selegiline induces a vascular alpha1- and alpha2-adrenoceptor-hyposensitivity that can be explained by the increase in noradrenaline release elicited by the drug.

Concentrations of platelet α2-adrenoceptors, lymphocyte muscarinic receptors, and blood monoamines in dogs (Canis familiaris) affected by canine cognitive dysfunction syndrome

“…Samples were immediately centrifuged at 240 x g for 20 min at room temperature to obtain the platelet rich plasma (PRP) fraction. The harvested PRP fractions were then ultra-centrifuged at 35 000 x g for 20 min at 4°C and the resulting pellets were re-suspended in a specific assay buffer (50 mM Tris-HCl, 0.5 mM MgCl 2 ; pH 7.4) and stored at -80°C until the  2 -adrenergic receptor binding assay was run (Pelat et al, 2001).…”

Clinical use of antidepressant therapy and associated cardiovascular risk

“…These agents result in enhanced concentrations of a broad range of central neurotransmitters, including norepinephrine 42. This may result in tachycardia and raised blood pressure, particularly if used in high doses.…”