Endocannabinoid System in Frog and Rodent Testis: Type-1 Cannabinoid Receptor and Fatty Acid Amide Hydrolase Activity in Male Germ Cells1

Abstract

N-arachidonoylethanolamide (anandamide [AEA]) is the main endocannabinoid described to date in the testis. It exerts its effects through the activation of G-protein coupled cannabinoid receptors (CNR). However, the activity of AEA in controlling male reproduction is still poorly known. Here we provide direct evidence on the presence of the "endocannabinoid system," constituted by type-1 cannabinoid receptor (CNR1) and fatty acid amide hydrolase (FAAH), in the frog Rana esculenta testis demonstrating its expression in tubular compartment. In fact, during the annual reproductive cycle, both proteins increase in September, when the appearance of spermatids (SPT) occurs. Immunocytochemistry confirms their localization in germ cells and, in particular, in elongated SPT. Signals are still present in spermatozoa (SPZ), as demonstrated by Western blot analysis. Furthermore, the activation of CNR1 reduces sperm motility. Comparative research, carried out using mouse and rat SPZ, definitely indicates that the endocannabinoid system operates in SPZ of phylogenetically distant species. A conserved physiological role of endocannabinoid system in controlling the inhibition of sperm motility is suggested.

Endocannabinoids affect the reproductive functions in teleosts and amphibians

“…In the frog gonads (Cobellis et al, 2006) the occurrence of both CB1 receptors and FAAH was reported, in agreement with the observations performed in rodent males (Cobellis et al, 2006). In…”

Marijuana, phytocannabinoids, the endocannabinoid system, and male fertility

“…This gradient is probably necessary to counteract CB1-dependant inhibition of motility and to keep spermatozoa quiescent until release [73]. Ricci et al [74] also concluded that CB1 receptors play a central role in preventing the acquisition of motility at too early a stage in the epididymis.…”

The endocannabinoid system in vertebrate male reproduction: A comparative overview

“…Feasible testicular AEA sources are Sertoli and germ cells since isolated mammalian immature Sertoli cells (Maccarrone et al, 2003) and mammalian and non mammalian spermatozoa (SPZ) (Maccarrone et al, 2005;Cobellis et al, 2006) produce endocannabinoids. The presence of AEA in the testis suggests that endocannabinoids are implicated in spermatogenesis and/or steroidogenesis.…”

“…Using a comparative approach, we have recently evidenced CB1 and FAAH in the testis of frogs (Cobellis et al, 2006) and rats (Cacciola G., Chioccarelli T., Mackie K., Meccariello R., Fasano S., Pierantoni R., Cobellis G., unpublished). Data confirm and/or extend previous studies carried out in mice demonstrating the presence of FAAH in isolated immature Sertoli cells (Maccarrone et al, 2003) and CB1 in Leydig (Wenger et al2001;Gye et al, 2005) and germ cells (from spermatogonia to SPZ) (Gye et al, 2005).…”