Dualism in the alpha-adrenoceptor blocking action of dihydroergocristine

Efficacy of acetylcholinesterase inhibitors versus nootropics in Alzheimer's disease: a retrospective, longitudinal study

The aim of this study was to investigate the efficacy of nootropics (piracetam, aniracetam, nimodopine and dihydroergicristine) versus acetylcholinesterase inhibitors (AChE-Is) (tacrine and donepezil) in the treatment of Alzheimer's disease. This is a retrospective study of 510 patients with Alzheimer's disease. To determine clinical efficacy of treatment, we used the mean change over time in scores for the following tests: the Mini-Mental State Examination (MMSE); the Cambridge Cognitive Examination for the Elderly; and the Functional Rating Scale for Symptoms of Dementia. In all patients and in patients with severe Alzheimer's disease (baseline MMSE < 11), no significant differences were seen in the neuropsychological test scores between the two treatment groups. In patients with moderate dementia (baseline MMSE between 11 and 20), however, there was a significantly greater deterioration, as shown on the CAMCOG scale, after 12 months' treatment for patients receiving AChE-Is compared with those receiving nootropics (-4.38 for AChE-Is group versus 1.48 for nootropics group). For patients with mild dementia (baseline MMSE score between 21 and 26), there was a significantly greater deterioration on the MMSE scale for each time-point in the nootropics group compared with the AChE-Is group. In conclusion, we did not find any strong evidence that a difference in efficacy exists between AChE-Is and nootropics in the treatment of Alzheimer's disease.

Effect of dihydroergocristine on blood pressure and activity at peripheral alpha-adrenoceptors in pithed rats

The effect of dihydroergocristine on blood pressure and peripheral alpha-adrenoceptors was examined in pithed rats. The pressor response to dihydroergocristine was reduced competitively by yohimbine and non-competitively by nifedipine, but not by prazosin or methysergide. These results show that vasoconstriction due to dihydroergocristine is mediated by alpha 2-adrenoceptors. Dihydroergocristine decreased the tachycardia elicited by electrical stimulation of the cardioaccelerator sympathetic nerves, this effect being antagonized by yohimbine. The pressor response to electrical stimulation of the spinal sympathetic outflow and to (-)-phenylephrine was reduced by dihydroergocristine suggesting competitive antagonism. It can be concluded that in pithed rats dihydroergocristine acts at the periphery as a competitive alpha 1-adrenoceptor blocker and an alpha 2-adrenoceptor agonist.

A comparison of the blocking effect of alpha-adrenoceptor antagonist drugs towards directly and indirectly acting agonists on the rat vas deferens

The antagonistic effect of dihydroergocristine and phentolamine towards the directly acting amine noradrenaline and the indirectly acting amine tyramine on the rat vas deferens was evaluated. It has been demonstrated that both alpha-adrenoceptor blocking drugs reduced the effect of the indirectly acting amine at concentrations lower than those needed to antagonize the action of noradrenaline. When concentrations of the alpha-adrenoceptor blocking drugs effective against noradrenaline were employed a qualitative difference in the antagonism towards the directly and indirectly acting amines has also been shown. It appears that in the rat vas deferens the effects induced by tyramine-released noradrenaline are more easily affected by alpha-adrenoceptor antagonist drugs than those induced by exogenously applied noradrenaline.