"Biologists have detected a cannabinoid receptor in spermatozoa. Endogenous cannabinoids that occur in both the male and the female genital tract activate the spermatozoa: they trigger the so-called acrosome reaction, during which the spermatozoon releases digestive enzymes and loses the cap on the anterior half of its head. Without this reaction, spermatozoa cannot penetrate the ovum.
During fertilization, a sperm must first fuse with the plasma membrane and then penetrate the female egg in order to penetrate it. To this end, sperm cells go through a process known as the acrosome reaction which is the reaction that occurs in the acrosome of the sperm as it approaches the egg. In the lab, this so-called acrosome reaction is considered a test for analysing the ability of semen to accomplish fertilisation.
A receptor for an endogenous cannabinoid plays a crucial role in this process. A team of biologists from Bochum and Bonn, headed by Prof Dr Dr Dr Hanns Hatt, have been the first one to provide a proof of the so-called G protein-coupled receptors 18 (GPR18) in spermatozoa, following a comprehensive analysis. They published their findings in Scientific Reports.
Researchers find 223 additional receptors
Specialised in olfaction research, the team from Bochum had detected as many as 60 olfactory receptors in spermatozoa early this year, and has activated and localised ten of them. "In the current study, we have focused on the remaining G protein-coupled receptors, which, rather than being olfactory receptors, bind other substances," explains Hanns Hatt..."
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