A review of fish pituitary LHRH receptor studies

International audienc

Administration of LHRH analogues in various ways: Effect on the advancement of spermiation in prespawning landlocked salmon, Salmo salar

During an experimental period of 12 days, the onset of spermiation, quantity of collectable milt, spermatocrit, plasma and pituitary gonadotropin hormone (GtH) were compared in control and LHRH analogue (LHRHa)-treated prespawning landlocked salmon. Des-Gly10-[D-Ala6]-LHRH ethylamide (D-Ala6-LHRH EA) was administered either by intraperitoneal multiple injections in saline or 40% propylene glycol or by a single intraperitoneal implant in silicone rubber. [6-(D-2-naphthylalanine)] LHRH (D-Nal (2)6-LHRH) was administered in a single cholesterol pellet. All the methods of administering LHRHa effectively accelerated the onset of spermiation and increased the volume of collectable milt. Study of the spermatocrit indicated that this increase is associated with an advancement in the production of spermatozoa and is not just due to sperm dilution. Furthermore, this increase in milt volume is related to an increase in plasma GtH. On the other hand, LHRHa treatments did not provoke any change in pituitary GtH content

Onset of gonadotropic hormone accumulation in the immature trout pituitary gland in response to estrogen or aromatizable androgen steroid hormones

A study was conducted to determine the specificity of the steroids able to cause a stimulation of pituitary gonadotropic hormone (GtH) levels in sexually immature rainbow trout. Low pituitary GtH levels characteristic of juvenile trout were rapidly elevated following treatment with estrogen and aromatizable androgenic steroid hormones, but nonaromatizable androgens and progestogenic steroids were ineffective. An aromatase inhibitor, 1,4,6-androstatrien-3,17-dione, significantly reduced the pituitary GtH increase in response to treatment with testosterone. A central effect of steroid hormones on pituitary GtH was confirmed by the fact that pituitary steroid implants did not increase liver weight as observed after perivisceral hormone treatment. The possible participation of sex steroids in a mechanism of initiation of gonad recrudescence or onset of pubertal gonadal development in salmonids is discussed

Stimulation of gonadotropin secretion by intraventricular injection of hypothalamic extracts in the goldfish, Carassius auratus

Goldfish serum gonadotropin (GTH) concentrations were determined by radioimmunoassay 20 min after injection of goldfish brain extracts or synthetic luteinizing hormone-releasing hormone (LH-RH) into the third ventricle in the ventrobasal hypothalamic region. Extracts of the cerebellum and medulla were ineffective. Synthetic LH-RH, and extract of the lateral hypothalamus each significantly increased plasma GTH levels. The results indicate that the hypothalamus of the sexually mature female goldfish contains gonadotropin releasing hormone activity, and that releasing hormone is effective when administered via the intrahypothalamic route

Studies of the biological activity of LHRH analogs in the rainbow trout, landlocked salmon, and the winter flounder

Also published in General and comparative endocrinology, v. 71, 1988, p. 372-38

Accelerated ovulation by pelleted LHRH analogue treatment of spring-spawning rainbow trout (Salmo gairdneri) held at low temperature

Accelerated ovulation by pelleted LHRH analogue treatment of spring-spawning rainbow trout (Salmo gairdneri) held at low temperatur

Use of LHRH analogs in aquaculture

Also published in LHRH and its analogs : contraceptive and therapeutic applications, Part 2. Lancaster, MTP Press, 1987, p. 489-49