This below study shows that forced swimming increases serotonin. I post this because often people claim that plasma serotonin and gut serotonin have an inverse relationship. This study shows that the severe stress that those young rats endured increased both their plasma and brain serotonin, and the brain serotonin was even more increasesd (150% and 250% respectively). Furthermore, serotonin increasd the permeability of the BBB, which could be prevented by p-CPA and cyproheptadine.
Increased blood-brain barrier permeability following acute short-term swimming exercise in conscious normotensive young rats. - PubMed - NCBI
"The status of the blood-brain barrier (BBB) was examined following short-term forced swimming (FS) exercise in younger rats (age 8–9 wks, 80–90 g). Subjection of animals to continuous FS for 30 min duration increased the permeability of the BBB to Evans blue albumin (EBA) and 131I-sodium in 5 and 8 brain regions, respectively. Extravasation of the tracers was markedly pronounced in the cerebellum followed by the cerebral cortex. EBA staining was confined mainly to the posterior cingulate cortex, parietal and occipital cortices, whole cerebellar vermis and the mediolateral cerebellar cortices as well as the dorsal surface of the hippocampus. In addition to the above brain regions, BBB permeability to 131I-sodium extended to the caudate nucleus, thalamus and hypothalamus. At this time period, the serotonin (5-hydroxytryptamine, 5-HT) content showed a profound increase in plasma and brain of about 150% and 250% respectively from the control value. Pretreatment with p-CPA (p-chlorophenylalanine, a serotonin synthesis inhibitor) prevented both the increased permeability of the BBB and the rise in plasma and brain 5-HT level. However, prior treatment with cyproheptadine (a 5-HT2 receptor antagonist) prevented the increased permeability alone. The 5-HT level continued to remain high. These results suggest that short-term FS increases BBB permeability in specific brain regions. This increased permeability appears to be mediated through serotonin via 5-HT2 receptors."
"...The probable mechanisms underlying BBB permeability in these conditions is only speculative. There are reasons to believe that neurochemical mediators could play an important role 57,58. Serotonin is one of the active neurochemical compounds which are involved in various stressful situations and in neurological diseases 1,17,24,39,45,57 Infusion of this amine in small amounts increases BBB permeability within 15 rain after its administration in young rats 49. Depletion of serotonin prior to traumatic injuries to brain and spinal cord significantly reduces microvascular permeability and edema in the perifocal traumatized regions 37,48. These data speak in favor of a chemical/receptor- mediated increase in BBB permeability."
"Forced swimming (FS) is a severe stressful condition 13,19,21,26,40,44. Alteration of cerebral circulation, vertebral artery injury, cerebellar stroke, and abnormal neurological function and behavior while swimming is well documented in the literature 50,53,54. However, the status of the BBB following swimming is not known. Swimming involves movement of head and body position for proper orientation and balance in the water 19. This activates the cerebellum and associated brain regions for co-ordinated limb movement 19,26.40 Specific activation of central serotonergic and catecholaminergic systems occurs in laboratory animals during swimming 21.40,44. Thus, it is likely that BBB permeability could also be modified during swimming in specific brain regions."
"The present results show, probably for the first time, that FS increases BBB permeability to protein tracers in specific brain regions which appears to be mediated through serotonin via 5-HT 2 receptors. This increase in BBB permeability was apparently confined to specific brain regions associated with the swimming mechanism 19,21. This indicates that the BBB may well be modified selectively following activation of specific brain regions 7.18,23,30 The selective regional increase in BBB permeability following FS is difficult to explain. It is likely that the regional activation of brain areas during FS could result in a local activation of 5-HT synthesis and release from the cerebral vessels. An increased release of local 5-HT could act through 5-HT 2 receptors, causing a transient increase in local BBB permeability. However, changes in local cerebral metabolism and blood flow following FS could also play an important role 1.7,11.16,38,44A6,47"
Increased blood-brain barrier permeability following acute short-term swimming exercise in conscious normotensive young rats. - PubMed - NCBI
"The status of the blood-brain barrier (BBB) was examined following short-term forced swimming (FS) exercise in younger rats (age 8–9 wks, 80–90 g). Subjection of animals to continuous FS for 30 min duration increased the permeability of the BBB to Evans blue albumin (EBA) and 131I-sodium in 5 and 8 brain regions, respectively. Extravasation of the tracers was markedly pronounced in the cerebellum followed by the cerebral cortex. EBA staining was confined mainly to the posterior cingulate cortex, parietal and occipital cortices, whole cerebellar vermis and the mediolateral cerebellar cortices as well as the dorsal surface of the hippocampus. In addition to the above brain regions, BBB permeability to 131I-sodium extended to the caudate nucleus, thalamus and hypothalamus. At this time period, the serotonin (5-hydroxytryptamine, 5-HT) content showed a profound increase in plasma and brain of about 150% and 250% respectively from the control value. Pretreatment with p-CPA (p-chlorophenylalanine, a serotonin synthesis inhibitor) prevented both the increased permeability of the BBB and the rise in plasma and brain 5-HT level. However, prior treatment with cyproheptadine (a 5-HT2 receptor antagonist) prevented the increased permeability alone. The 5-HT level continued to remain high. These results suggest that short-term FS increases BBB permeability in specific brain regions. This increased permeability appears to be mediated through serotonin via 5-HT2 receptors."
"...The probable mechanisms underlying BBB permeability in these conditions is only speculative. There are reasons to believe that neurochemical mediators could play an important role 57,58. Serotonin is one of the active neurochemical compounds which are involved in various stressful situations and in neurological diseases 1,17,24,39,45,57 Infusion of this amine in small amounts increases BBB permeability within 15 rain after its administration in young rats 49. Depletion of serotonin prior to traumatic injuries to brain and spinal cord significantly reduces microvascular permeability and edema in the perifocal traumatized regions 37,48. These data speak in favor of a chemical/receptor- mediated increase in BBB permeability."
"Forced swimming (FS) is a severe stressful condition 13,19,21,26,40,44. Alteration of cerebral circulation, vertebral artery injury, cerebellar stroke, and abnormal neurological function and behavior while swimming is well documented in the literature 50,53,54. However, the status of the BBB following swimming is not known. Swimming involves movement of head and body position for proper orientation and balance in the water 19. This activates the cerebellum and associated brain regions for co-ordinated limb movement 19,26.40 Specific activation of central serotonergic and catecholaminergic systems occurs in laboratory animals during swimming 21.40,44. Thus, it is likely that BBB permeability could also be modified during swimming in specific brain regions."
"The present results show, probably for the first time, that FS increases BBB permeability to protein tracers in specific brain regions which appears to be mediated through serotonin via 5-HT 2 receptors. This increase in BBB permeability was apparently confined to specific brain regions associated with the swimming mechanism 19,21. This indicates that the BBB may well be modified selectively following activation of specific brain regions 7.18,23,30 The selective regional increase in BBB permeability following FS is difficult to explain. It is likely that the regional activation of brain areas during FS could result in a local activation of 5-HT synthesis and release from the cerebral vessels. An increased release of local 5-HT could act through 5-HT 2 receptors, causing a transient increase in local BBB permeability. However, changes in local cerebral metabolism and blood flow following FS could also play an important role 1.7,11.16,38,44A6,47"
