Alterations of 3,4-dihydroxyphenylethylamine and its metabolite 3,4-dihydroxyphenylacetic produced in rat brain tissues after systemic administration of saxitoxin.

We have measured the dopamine levels in some discrete rat brain regions after acute intraperitoneal administration of saxitoxin (STX). STX is one of the several toxins that causes paralytic shellfish poisoning (PSP). PSP is a serious public health concern through the world. Certain dinoflagellates are able of producing STX, a powerful neurotoxic compound, which blocks the voltage sensitive sodium channels, entailing to the appearance of the main symptoms of poisoning by PSP: muscular paralysis and respiratory depression. The goal in this study was to analyze the effect of STX on dopamine levels in discrete rat brain regions after its acute intraperitoneal administration. Different experimental periods were analyzed for STX doses (5 and 10 µg kg(-1) body weight). With low dose, experimental periods were: 30, 60 and 120 min. With high dose, experimental period was just 30 min. At the end of each experimental period, animals were sacrificed by cervical dislocation. Brains were removed and dissected in: hypothalamus, striatum, midbrain, brain stem, right and left hemispheres. This is to our knowledge, the first report in which a sublethal dose of STX administered intraperitoneally results in an acute alteration of dopamine (DA) production and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC).

Effects of systemic administration of saxitoxin on serotonin levels in some discrete rat brain regions.

The present study is related with the toxicity of Saxitoxin (STX), a neurotoxic compound, produced by certain dinoflagellates. Its main toxicological activity is observed through the blockage of the sodium channels. It might originate a reduction of the amplitude and speed of conduction of the action potentials by the peripheral and central nerves, as well as weakening of the skeletal muscular contraction. The aim of this study was to analyze the effect of STX on serotonin (5-HT) levels in some discrete rat brain regions after acute intraperitoneal (i.p.) administration of 5 and 10 microg Kg(-1) STX body weight. 5-HT levels were analyzed at 30, 60 and 120 min after the administration of 5 microg Kg(-1) of STX, and 30 min after administration of 10 microg K(-1) of the toxin. Animals were sacrificed by cervical dislocation and the brains were removed and dissected in seven regions. Tissue samples were analyzed by using a chromatographic technique with electrochemical detection (HPLC/ED). Our results suggest that systemic administration of the STX reaches the brain producing alterations in neurotransmission increasing the levels of 5-HT in all the brain regions studied. With respect to the serotonin metabolite, 5-hidroxiindoleacetic acid (5-HIAA), we observed an increase in its levels in all the brain regions studied with the high dose of toxin, whereas different alterations were observed with the low dose of toxin.