Interaction of α-melanotropin (α-MSH) and noradrenaline in the median eminence in the control of female sexual behavior

• Published in: Peptides (New York, N.Y. : 1980) N.Y. : 1980), 2000-02, Vol.21 (2), p.219-223
• Main Authors: Scimonelli, Teresa, Medina, Favio, Wilson, Catherine, Celis, Marı́a Ester
• Format: Article
• Language: English
• Subjects: Adrenalectomy; Adrenergic alpha-Antagonists - pharmacology; Adrenergic beta-Antagonists - pharmacology; alpha-MSH - metabolism; alpha-MSH - pharmacology; Animals; beta receptors; Dopamine - pharmacology; Female; Female sexual behavior; Male; Median eminence; Median Eminence - drug effects; Metoprolol - pharmacology; Noradrenaline; Norepinephrine - metabolism; Norepinephrine - pharmacology; Ovariectomy; Posture; Prazosin - pharmacology; Propranolol - pharmacology; Rats; Rats, Wistar; Sexual Behavior, Animal - drug effects; α-MSH
• ISSN: 0196-9781; 1873-5169
• DOI: 10.1016/S0196-9781(99)00191-6

In the present study, we examined the effects of the injection of α-melanotropin (α-MSH), noradrenaline (NA), and dopamine in the median eminence of ovariectomized-adrenalectomized rats on female sexual behavior. The animals were primed with l0 μg of estradiol benzoate, and 52–54 h later they were injected into the median eminence with either 1 μl of artificial cerebrospinal fluid, 1 μg/rat α-MSH, 200 ng/rat NA, 200 ng or 2 μg/rat dopamine, in 1 μl of artificial cerebrospinal fluid. Both α-MSH and NA significantly stimulated sexual behavior. This effect was antagonized by two β-adrenergic antagonists: propranolol (500 ng/rat) and metoprolol (400 ng/rat) applied 15 min before the α-MSH or NA. The α-adrenergic antagonist prazosine (500 ng/rat) was ineffective in reducing the effect of α-MSH. The vehicle and dopamine at both doses had no effect on sexual activity. These results indicate that α-MSH and NA in the median eminence stimulate female sexual behavior and that NA mediates the action of α-MSH via β-receptors.