Effects of N-methyl-D,L-aspartate (NMA) on growth hormone and thyroid hormone levels in steroid-primed immature rainbow trout (Oncorhynchus mykiss)
✍ Scribed by Holloway, Alison C.; Leatherland, John F.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 77 KB
- Volume
- 279
- Category
- Article
- ISSN
- 0022-104X
No coin nor oath required. For personal study only.
✦ Synopsis
In this study we investigate whether the stimulatory action of the glutamate agonist, N-methyl-D,L-aspartate (NMA) on growth hormone (GH) levels in rainbow trout (Oncorhynchus mykiss) is steroid hormone-dependent. NMA was administered to sexually immature juvenile rainbow trout that had been primed with testosterone (T), 17β-estradiol (E 2 ) or 5αdihydrotestosterone and changes in plasma growth hormone (GH) concentrations were measured. NMA had no significant effect on the plasma GH concentrations of non-steroid hormone-primed trout (controls), although in both T-and E 2 -primed fish plasma GH levels were elevated 6 hours following NMA administration. The response had disappeared by 24 hours in the T-primed group, but was still evident in the E 2 -primed fish. In comparison, in the 5αDHT-primed fish, NMA significantly depressed plasma GH levels 6 hours post-injection (P < 0.05), but this effect had disappeared 24 hours after NMA administration.
NMA had no effect on plasma T 4 levels in any treatment group, and although plasma T 3 levels were significantly (P < 0.05) depressed in T-primed fish 6 hours post-injection, this response was not seen in any other group. These results suggest that NMA has no effect on plasma thyroid hormone levels but it does have a steroid hormone-dependent action on plasma GH levels in rainbow trout.