Gonadotropin-releasing hormone agonist blocks anxiogenic-like and depressant-like effect of corticotrophin-releasing hormone in mice

Corticotrophin-releasing factor (CRF) is reported to inhibit the release of gonadotropin-releasing hormone (GnRH). In addition to the endocrine effects, GnRH is reported to influence the behavior via its neuronal interactions. We therefore, hypothesized that anxiety and depression produced by CRF could be also subsequent to the decrease in GnRH. To support such possibility, we investigated the influence of GnRH agonists on CRF or CRF antagonist induced changes in social interaction time in social interaction test, and immobility time in forced swim test in mice, as the indices for anxiety and depression, respectively. Results indicated that GnRH agonists [leuprolide (20–80 ng/mouse, i.c.v.), or d-Trp-6-LHRH (40–160 ng/mouse, i.c.v.)] dose dependently increased social interaction time and decreased immobility time indicating anxiolytic- and antidepressant-like effect, respectively. Such effects of GnRH agonists were even evident in castrated mice, which suggest that these effects were unrelated to their endocrine influence. Administration of CRF (0.1 and 0.3 nmol/mouse, i.c.v.) produced just opposite effects as that of GnRH agonist on these parameters. Further, it was seen that pretreatment with leuprolide (10 or 20 ng/mouse, i.c.v.) or d-Trp-6-LHRH (20 or 40 ng/mouse, i.c.v.) dose dependently antagonized the effects of CRF (0.3 nmol/mouse, i.c.v.) in social interaction and forced swim test. CRF antagonist [α-Helical CRF (9–41), (1 or 10 nmol/mouse, i.c.v.)] was found to exhibit anxiolytic- and antidepressant-like effect, and its sub-effective dose (0.1 nmol/mouse, i.c.v.) when administered along with sub-threshold dose of leuprolide (10 ng/mouse, i.c.v.), or d-Trp-6-LHRH (20 ng/mouse, i.c.v.) also produced significant anxiolytic- and antidepressant-like effect. These observations suggest reciprocating role of GnRH in modulating the CRF induced anxiogenic- and depressant-like effects.