PCA Neurotoxin Administration — LA Mamounas | ReplicateScience

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PCA Neurotoxin Administration — LA Mamounas | ReplicateScience

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A pathology of brain serotonergic (5-HT) systems has been found in psychiatric disturbances, normal aging and in neurodegenerative disorders including Alzheimer's and Parkinson's disease. Despite the clinical importance of 5-HT, little is known about the endogenous factors that have neurotrophic influences upon 5-HT neurons. The present study examined whether chronic pain parenchymal administration of the neurotrophins brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) or NGF could prevent the severe degenerative loss of serotonergic axons normally caused by the selective 5-HT neurotoxin p-chloroamphetamine (PCA). The neurotrophins (5–12 micrograms/d) or the control substances (cytochrome c or PBS vehicle) were continuously infused into the rat frontoparietal cortex using an osmotic minipump. One week later, rats were subcutaneously administered PCA (10 mg/kg) or vehicle, and the 5-HT innervation was evaluated after two more weeks of neurotrophin infusion. As revealed with 5-HT immunocytochemistry, BDNF infusions into the neocortex of intact (non-PCA-lesioned) rats caused a substantial increase in 5-HT axon density in a 3 mm diameter region surrounding the cannula tip. In PCA-lesioned rats, intracortical infusions of BDNF completely prevented the severe neurotoxin-induced loss of 5-HT axons near the infusion cannula. In contrast, cortical infusions of vehicle or the control protein cytochrome c did not alter the density of serotonergic axons in intact animals, nor did control infusions prevent the loss of 5-HT axons in PCA-treated rats. NT-3 caused only a modest sparing of the 5-HT innervation in PCA-treated rats, and NGF failed to prevent the loss of 5-HT axon density. The immunocytochemical data were supported by neurochemical evaluations which showed that BDNF attenuated the PCA-induced loss of 5-HT and 5- HIAA contents and 3H-5-HT uptake near the infusion cannula. Thus, BDNF can promote the sprouting of mature, uninjured serotonergic axons and dramatically enhance the survival or sprouting of 5-HT axons normally damaged by the serotonergic neurotoxin PCA.

Protocol Steps

1

Osmotic minipump implantation and neurotrophin infusion initiation

Osmotic minipumps delivering neurotrophins (BDNF, NT-3, or NGF at 5-12 micrograms/d) or control substances (cytochrome c or PBS vehicle) were implanted to continuously infuse into the rat frontoparietal cortex

Continuous infusion for 3 weeks totalNot specified

Note: Infusion cannula placement in frontoparietal cortex; baseline timepoint for subsequent PCA administration

View evidence from paper

“The neurotrophins (5–12 micrograms/d) or the control substances (cytochrome c or PBS vehicle) were continuously infused into the rat frontoparietal cortex using an osmotic minipump”

2

PCA or vehicle administration

One week after osmotic minipump implantation, rats were subcutaneously administered either PCA (10 mg/kg) or vehicle control

Single administration at 1 week post-pump implantationNot specified

Note: Timing allows for establishment of neurotrophin infusion before neurotoxic challenge

View evidence from paper

“One week later, rats were subcutaneously administered PCA (10 mg/kg) or vehicle”

3

Continued neurotrophin infusion

Neurotrophin infusion continued for two additional weeks following PCA or vehicle administration

2 weeks post-PCA administrationNot specified

Note: Total infusion period is 3 weeks; 2 weeks of infusion occur after PCA administration

View evidence from paper

“the 5-HT innervation was evaluated after two more weeks of neurotrophin infusion”

4

5-HT immunocytochemistry evaluation

Serotonergic axon density was evaluated using 5-HT immunocytochemistry in a 3 mm diameter region surrounding the cannula tip

At 3 weeks post-pump implantation (2 weeks post-PCA)Not specified

Note: Primary outcome measure for assessing neurotrophin effects on 5-HT axon density and PCA-induced degeneration

View evidence from paper

“As revealed with 5-HT immunocytochemistry, BDNF infusions into the neocortex of intact (non-PCA-lesioned) rats caused a substantial increase in 5-HT axon density in a 3 mm diameter region surrounding the cannula tip”

5

Neurochemical evaluation

Neurochemical assessments were performed to measure 5-HT and 5-HIAA contents and 3H-5-HT uptake near the infusion cannula

At 3 weeks post-pump implantation (2 weeks post-PCA)Not specified

Double Cannula System Pack

Double Cannula System Pack

Matches: Infusion cannula

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Note: Supportive biochemical measures to confirm immunocytochemical findings

View evidence from paper

“The immunocytochemical data were supported by neurochemical evaluations which showed that BDNF attenuated the PCA-induced loss of 5-HT and 5-HIAA contents and 3H-5-HT uptake near the infusion cannula”