Central pool of serotonin and tail-flick latency during two phases of biphasic fever in rats.

In experiments on male Wistar rats, the acute phase reaction was induced by a bolus intravenous injection of Escherichia coli lipopolysaccharide (10 microg/kg) through a silicon catheter pre-implanted into the jugular vein. The colonic and skin temperature was measured with thermocouples. Changes in nociception were assessed based on tail flick latency (TFL) in response to a noxious heat stimulus. In this work, we observed the development of biphasic fever and phasic changes in TFL, namely, hyperalgesia in the first period of the acute phase reaction and hypoalgesia in its second phase. The catabolism of serotonin increased most considerably in the initial period of the acute phase reaction in the midbrain, striatum, and rostrodorsomedial medulla (on average, by 20-25%, 35-40%, and 95-100%, respectively). In the second phase of the acute phase reaction, despite a significant increase in the serotonin content in the striatum, midbrain, and cerebellum, there were no significant changes in serotonin catabolism in these parts of the CNS, which coincided with hypoalgesia. Thus, the phasic changes in TFL and colonic temperature after initiation of the acute phase reaction were accompanied by determinate changes in the catabolism of serotonin in different brain parts.

[Serotonin metabolism in different areas of the brain and spinal cord in post-vibration hypotonia]. / Metabolizm serotonina v razlichnykh oblastiakh golovnogo i spinnogo mozga pri postvibratsionnoi gipotonii.

General vertical vibration enhanced the lability of the vascular tone in adult male rats. Quite often a decrease in AP occurred in rats with high initial blood arterial pressure. The data obtained suggests that the neurochemical mechanisms of post-vibration hypotony and the hypotony in control animals are different.

[Biogenic amines in the small intestines in guinea pigs in simulated weightlessness and vibration]. / Biogennye aminy tonkoi kishki morskikh svinok v usloviiakh, modeliruiushchikh ponizhennyiu vesomost, i pri vibratsii.

The dynamics of changes in epinephrine (E), norepinephrine (NE), dopamine (DA), serotonin (5-HT) and its metabolite 5-HIAA in the duodenal and iliac wall was studied in the initial period of support unloading (the "dry" immersion method) and general low frequency vibration (LFV). It was found that 15-min unloading led to a sharp increase in 5-HT and DA in the duodenum, accompanied by an elevation in total electrical activity of smooth muscles, to a decrease in E, NE, and DA and, in contrast, to an increase in 5-HT and 5-HIAA in the ileum. Normalization of monoamine metabolism observed 2 h after the beginning of the unload 4 hour later was followed by inactivation of duodenal serotoninergic structures and iliac adrenergic structures. The LFV induced mostly the opposite response, decreasing 5-HT in the duodenum with accumulation of E and NE in it, and a more marked activation of inhibitory adrenergic innervation of the ileum.