Interaction of alpha-melanotropin (alpha-MSH) and noradrenaline in the median eminence in the control of female sexual behavior.
In the present study, we examined the effects of the injection of alpha-melanotropin (alpha-MSH), noradrenaline (NA), and dopamine in the median eminence of ovariectomized-adrenalectomized rats on female sexual behavior. The animals were primed with l0 microg of estradiol benzoate, and 52-54 h later they were injected into the median eminence with either 1 microl of artificial cerebrospinal fluid, 1 microg/rat alpha-MSH, 200 ng/rat NA, 200 ng or 2 microg/rat dopamine, in 1 microl of artificial cerebrospinal fluid. Both alpha-MSH and NA significantly stimulated sexual behavior. This effect was antagonized by two beta-adrenergic antagonists: propranolol (500 ng/rat) and metoprolol (400 ng/rat) applied 15 min before the alpha-MSH or NA. The alpha-adrenergic antagonist prazosine (500 ng/rat) was ineffective in reducing the effect of alpha-MSH. The vehicle and dopamine at both doses had no effect on sexual activity. These results indicate that alpha-MSH and NA in the median eminence stimulate female sexual behavior and that NA mediates the action of alpha-MSH via beta-receptors.
Scimonelli
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Laboratorio de Fisiología, Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, CP 5000 Ciudad Universitaria, Córdoba, Argentina. tscimonelli.epractica@mater.fcm.unc.edu.ar
Medina
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Wilson
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Celis
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ME
D000315:Adrenalectomy; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004298:Dopamine / Q000494:pharmacology; D005260:Female; D008297:Male; D008473:Median Eminence / Q000187:drug effects*; D008790:Metoprolol / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism* / Q000494:pharmacology; D010052:Ovariectomy; D011187:Posture; D011224:Prazosin / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D000521:alpha-MSH / Q000378:metabolism* / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D000521:alpha-MSH; D011433:Propranolol; D008790:Metoprolol; D004298:Dopamine; D009638:Norepinephrine; D011224:Prazosin