It looks like oral doses of Neem derivatives have significant effect on testosterone:

- this study showed Neem leaves halved testosterone in male rats and greatly affected sperm: https://www.researchgate.net/publicatio ... of_neem_Az adirachta_indica_on_the_hormonal_milieu_of_male_ra ts

- and Neem bark did the same: file:///E:/Downloads/effect%20of%20methanolic%20neem%20bark%20extract%2 0on%20the%20testicular%20parameters%20of%20adult%2 0sprague%20dawley%20rats.pdf

- Neem rind reduced testicle size by 90%: file:///E:/Downloads/effect%20of%20methanolic%20neem%20bark%20extract%2 0on%20the%20testicular%20parameters%20of%20adult%2 0sprague%20dawley%20rats.pdf

Injection of the oil into the vas deference seemed to cause prolonged sterilization and "significant reduction in testicular size": http://www.ncbi.nlm.nih.gov/pubmed/8226307

Now the problem is that there is some inconsistency between what the various plants do, and long term use of these probably cause other problems with kidneys, blood pressure, pancreas and such, and there is always potential for allergic reactions when taking a foreign food item. But it still looks quite effective at disrupting testicle function.

Anyone tried it?

Here's also a table of various plants extracts that can castrate: http://www.ncbi.nlm.nih.gov/pmc/article ... able/tbl2/

Only the injection seems to be have an effect, more such of glue, I think.

I cant find any other descriptions about a castrating effects or so!?

CastratedTomcat (imported) wrote: Sun Jan 17, 2016 8:21 am Only the injection seems to be have an effect, more such of glue, I think.

I cant find any other descriptions about a castrating effects or so!?

What do you mean, there are lots of links about Neem drastically reducing testosterone production. That is a castrating effect. And by eating the rind the testicles shrunk by 90%! Why do you say that's not a castrating effect?

I have not found informations about a lowering of testosterone with it.

Do you have a link? It sounds interesting and oral is also good, I dont like injections!

The links above are not so clear and two, I think the most interesting links, are links to the harddrive in your computer, not weblinks.

Bit of text:

The experiment was conducted to determine the effect of methanolic neem bark extract (Azadirachta

indica) on some reproductive parameters of male Sprague – Dawley rats. Twenty adult Sprague-Dawley

rats were used weighing between 120 – 160g. They were randomly allocated to 4 groups with 5 animals in

each group. Rats in groups A, B, and C received 100 mg/kg, 200 mg/kg and 400 mg/kg of methanolic

neem bark extract respectively. Group D (control) was administered with distilled water daily. The

duration of administration was for 56 days (56d). At the end of the experiments, the rats were sacrificed

using chloroform. Testes were excised, weighed and fixed in Bouin’s fluid and were later processed for

further histological examinations. Blood was collected through cardiac puncture, centrifuged and was

assayed for serum testosterone analysis using the ELISA kit. Result on testicular histology showed a

significant distortion of the testicular tubular epithelium in all the treated groups with a reduction in

interstitial cell of Leydig. There was an insignificant increase in testicular weight in the treated groups

when compared with the control group. Double tail sperm morphology and reduced sperm motility was

observed in all the treated groups. Also the serum testosterone levels showed a significant decrease in

all treated groups compared to the control (p<0.05). The results of the study suggested that Azadirachta

indica bark extract has a deleterious effect on semen and the studied reproductive parameters in male

rats.

Link, which is a PDF file:

http://www.interesjournals.org/full-art ... w=download

You may have to rename the file and add a .pdf to it when it downloads. Mine came in with no file extension.

That paper doesn't actually say how the neem extract was given - intratesticular injection, oral, no idea. They're more explicit about the last study, which used neem oil, not extract; it was injected into the lumen of the vas deferens. This one doesn't say anything about how the rats were dosed.