Melatonin Enhances Gaba-Mediated Effects When Administered by Micropressure Ejection in Single Unit Neuronal Recordings

Abstract

Melatonin is produced by the pineal gland in rhythmic manner, with peak levels occurring during the dark periods in the circadian cycle, being almost undetectable during the light phase (1). Though it is widely accepted that melatonin influences the reproductive system (2), little is known on its mechanism of action. One of the possible hypotheses is that some better fitness with darkness is obtained during the interaction of melatonin with the responsive elements, where a tonic action is exerted during the dark phase of the photocycle. Even in terms of this probably inaccurate picture, the pattern of this fluctuating hormone has to fulfill some important requirements, bearing in mind the possible correlations to some other, more or less fluctuating rhythm in the activities of the Central Nervous System (CNS). Considering what has been observed in more than twenty years of research, oscillatory patterns are most common functional expression from single cells up to entire neuronal networks (3,4,5,6) and that these “regularly” fluctuating patterns have been demonstrated in cultured single cells (7,8), in brain slices (9) and entire animals (10), it appears interesting to look for the obligatory concordance that has to exist among all these rhythms. On account of the diversity of rhythms and the hypothesis of organic accordance, some ground of common interaction or of mutual influence has to be revealed. It seems too, that oscillations or at least more or less providable fluctuations are given to ameliorate compatibility with environmental fluctuations. The system is sufficiently rigid to express constant windows of parameters and in the meanwhile it has to be free to face all the variations or sudden changes either from its internal compartments or from external neighbourhood.