Phe-Met-Arg-Phe-amide (FMRF amide) stimulated growth hormone secretion in conscious OVX rats

Abstract

The presence of FMRF amide (Phe-Met-Arg-Phe-amide)-like immunoreactivity in neuronal elements in the hypothalamus suggested a role for this in the hypothalamic control of the anterior pituitary function. We report here the action of FMRF amide on growth hormone release following intracerebroventricular administration to rats. The injection of 200 ng (313.8 picomoles) of FMRF amide (in 2 ul) produced a significantly increased plasma GH 15 min after injection. The GH-increasing effect of 400–800 ng (627–1255 picomoles) of FMRF amide was already developed after 5 min and lasted up to 30 min. No change was detected in the plasma FSH, LH and prolactin levels at any time during the experimenal period. The intravenous administration of 10, 30 or 100 ug of FMRF amide had no effect on the plasma GH level. We conclude that FMRF amide can act at low doses to increase GH release through the inhibition of somatostatin release or the stimulation of GRF. We could not exclude a direct site of action in the pituitaries.