Effects of phenolic monoamines on release of luteinizing hormone stimulated by gonadotropin-releasing hormone and on plasma adrenocorticotropic hormone, norepinephrine, and cortisol concentrations in wethers.

Eighteen Suffolk and Suffolk x Hampshire wethers (56.3 +/- 1.3 kg) were used to determine the effects of naturally occurring amines, N-methyl-beta-phenethylamine (NMP) and tyramine (T), on plasma cortisol, norepinephrine (NE), ACTH, and GnRH-stimulated LH concentrations. In each experiment, wethers were assigned randomly to treatments with six replicates/treatment. In Exp. 1, treatments consisted of saline, 2 mg of NMP/kg BW (NMP2), or 4 mg of NMP/kg BW (NMP4). In Exp. 2, treatments consisted of saline, 4 mg of NMP/kg BW (N), or 2 mg of NMP + 4 mg of T/kg BW (NT). All treatments were given via indwelling jugular catheters in single doses of 2 mL. In Exp. 1, no effects of time after treatment on response were detected. The NMP2 wethers had lower cortisol and LH peak amplitudes (PKAMP) than other wethers (P < .03 and .05, respectively). Time to peak (PKT) concentration of NE was significantly shorter in NMP4-treated wethers (P < .004). In Exp. 2, significant interactions between time and treatment were detected for cortisol, NE, and LH. Cortisol and NE concentrations were increased (P < .0001 and P < .03, respectively) in N- and NT-treated wethers compared with controls, whereas LH was reduced (P < .003). The N and NT treatments increased cortisol PKT, peak height (PKHT), and PKAMP above that of controls (P < .02, < .006, and < .02, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)