[Seasonal changes in cardiovascular indices and monoamine content in the brain of rabbits]

In our previous studies a rather substantial difference between the initial values of the cerebral blood flow was found. On the other hand the brain monoamine content varies in different months of the year when studied. Comparative analysis of these parameters in rabbit brain was the aim of this paper. The content of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) in cortical and subcortical structures and the local cerebral blood flow (ICBF), the systemic arterial pressure (SAP) and pulse rate (PR) were studied. There were found seasonal variations in all parameters. A certain LCBF retardation in subcortical structures and cortex and the weakest effect of the stimulation was observed in May. There was a drop in SAP and some PR increase in the spring (April-May). Brain NA and 5-HT content showed seasonal changes with the lowest values near the winter months and reaching maximum in May as the PR does. Content of DA was low in May. So it seams possible that the ion ICBF in May can be explained by the decrease of brain DA at that time. The ICBF and the reactivity of cerebral microvessels seem to depend on the monoamine content and show seasonal variability.