The short answer is No. Poppy seeds themselves are inert, and contain no alkaloids.

The long answer on the other hand, is well... kind of. It is possible for sap to "leak" on to the seeds from inside the seed pod, coating them with miniscule amounts of alkaloids. This is documented in the many cases of positive drug tests resulting from the consumption of poppy seed food products.

Some people have tried soaking large quantities of poppy seeds (several hundered grams) in water, lemon juice etc, and then drinking the liquid the seeds were soaked in. Mild effects have been reported as a result. Often as not though, those who have tried this method have reported back no effects at all. While it has been argued that It could be just a placebo effect, this is likely not the case. It is not recommended that anyone try this looking for a cheap "legal high" -- there has been at least one recorded incidence of a young man dying after consuming poppy seed tea. So beware.

In the end, most people tend to think that even if minor effects can be obtained, given the massive quantities of poppyseed required it is not worth the hassle, waste, and potential exposure to other unknown substances in the seeds.