Quinolinic acid: effects on brain catecholamine and c-AMP content during L-dopa and reserpine administration.

The catecholamine content in rat brain tissue was determined following the administration of quinolinic acid alone or combined either with L-dopa and decarboxylase inhibitor or reserpine. Quinolinic acid alone decreased the levels of dopamine and noradrenaline, as well as those of c-AMP, and increased those of adrenaline. Treatment with L-dopa/decarboxylase inhibitor reversed the suppressing effect of quinolinic acid on dopamine, but not on noradrenaline. Reserpine alone depleted the contents of dopamine, noradrenaline and adrenaline. It could be concluded from the effects of quinolinic acid and reserpine given together that quinolinic acid suppresses the depletion of amines induced by reserpine. It has been demonstrated that quinolinic acid leads to injuries of nerve-cell bodies in pars compacta of the substantia nigra and in the striatum. Quinolinic acid is a natural metabolite of tryptophan, normally occurring in the liver, kidney and brain (Wolfensberger et al. 1983; Moroni et al. 1984). This compound exhibits convulsant and neuron excitant properties (Stone et al. 1987). It induces a selective pattern of neuronal degeneration both at the site of intracerebral injection (Schwarcz et al. 1983; Stone et al. 1987) and after general (intracardiac) administration (Beskid and Markiewicz 1988). The ability of quinolinic acid to produce neurotoxicity was greater in the striatum than in other parts of the brain. This prompted us to study catecholamine and c-AMP levels in rat brain tissue following quinolinic acid and L-dopa administration, as well as the influence of reserpine on quinolinic acid action.

[Morphological picture of the spinal ganglia in guinea pigs exposed to general vibration]. / Morfologiczny obraz zwojów rdzeniowych swinek morskich poddanych oddzialywaniu ogólnej wibracji.

In the spinal ganglia of guinea pigs exposed to general vibration of 40 Hz frequency and 1 mm amplitude for 3 hrs daily, gradually increasing morphological lesions were found after 7, 14, 30 and 90 days of the experiment. The animals exposed to vibration for up to 30 days exhibited a decrease in the cell nuclei volume, increase in the occurrence of eccentric and marginal cell nuclei and nucleoli, as well as an increase in the number of multiple nucleoli. After 90 days' exposure, such severe lesions as tigrolise, vacuolar degeneration of the cytoplasm, granular disintegration of the myelin sheaths or proliferation of glial cells were found.

[Vibration-induced morphological changes in the brain stem and spinal cord of the guinea pig]. / Zmiany morfologiczne w pniu mózgu i rdzeniu kregowym swinek morskich pod wplywem wibracji.

Some disorders of the brain stem and spinal cord microcirculation were observed in male adult guinea pigs exposed to vertical vibration of frequency 40 Hz and amplitude 1 mm for 3 hours daily during 7, 14, 30 days. These changes after 7 days of vibration were seen as congestion with single small haemorrhages and after 14 days as diffuse spongiosis of the brain stem and spinal cord. After 30 days both congestion with haemorrhages and spongiosis were noted but the first predominated.

Quinolinic acid: a modulator of the heart calcium channel in the rat and a binder of calcium ions.

When rat heart preparations were perfused with quinolinic acid at a slow constant rate, a decrease in contractility was observed. A higher rate of perfusion resulted in a biphasic response, thus both a positive inotropic effect and then a decrease in heart contractility were visible. Using a polarographic method, the association constant of quinolinic acid with calcium ions (Ka) was found to be equal to 220. By combining the values from heart perfusion experiments with the calculated ones of free calcium ions, a linear correlation was obtained between the decreases of contractility and of calcium ions (r = 0.94).

Quinolinic acid: effect on 45Ca content in perfused rat heart preparations and its calcium ion binding property in Krebs-Henseleit medium and blood serum.

In the experiment it was found that quinolinic acid perfusion was accompanied with the increase in calcium 45Ca content in myocardium tissue. The increase in calcium content was associated with a decrease in heart contractility. Moreover, it was shown that quinolinic acid can form complexes with calcium ions in Krebs-Henseleit medium as well as in blood serum but only to a small degree.