The expression of gonadotrophin-releasing hormone receptor (GnRH-R) in germinal cells of mouse testis, whole testes, pituitary glands, and mouse ovaries was determined by means of Northern hybridization using a mouse GnRH-R [(32)P]-labelled cDNA probe. Also, the expression of GnRH-R in rat germinal cells, testis and pituitary gland was determined by Northern blot analysis using the same mouse-specific probe. Three receptor transcripts were detected in all cases. In mouse pituitary, ovary and testis, we found two GnRH-R transcripts in the proximity of 4.6-4.7 and 3.4 kb, as well as a 1.6 kb transcript in the pituitary and a 2.0-2.1 kb transcript in both the ovary and testis. Mouse germ cells also exhibited three GnRH-R transcripts of 4.7, 3.5 and 2.2 kb. Two distinct GnRH-R transcripts were also detected in the rat pituitary (4.6 and 2.1 kb), testis (4. 7 and 3.5 kb) and germ cells (4.5 and 3.5 kb). In addition, a third transcript was detected in rat pituitary (1.9 kb) and in rat testis and germinal cells (2.1 kb). The present study demonstrates that GnRH-R mRNA is expressed in rat and mouse testicular germ cells. We suggest that GnRH-R present in these cells may interact with GnRH or GnRH-like peptides produced in the testis and may be part of a paracrine system. The presence of multiple GnRH-R encoding transcripts is also of interest and warrants further studies to evaluate their regulation and function.