Saw palmetto is an indirectly acting sympathomimetic in the rat-isolated prostate gland.
BACKGROUND
To investigate whether saw palmetto that inhibits alpha1-adrenoceptor binding in vitro affects contractility of the rat prostate gland.


METHODS
The effects of a commercially available saw palmetto extract were examined on the contractility of rat-isolated prostate glands. The extract was tested in the presence and absence of phentolamine, prazosin, yohimbine, propranolol, hexamethonium, cocaine, desipramine, nifedipine, guanethidine, atropine, and alpha,beta-methylene ATP to evaluate the mechanism of action. Isolated preparations of rat vas deferens and bladder were used for comparison.


RESULTS
Unexpectedly, saw palmetto extract caused contractions of the rat prostate gland that could be attenuated by prazosin, phentolamine, nifedipine, guanethidine, cocaine, and desipramine but not by any of the other pharmacological tools. Similar contractile effects were observed in rat-isolated vas deferens preparations but not in rat-isolated bladder preparations.


CONCLUSIONS
In the rat prostate gland, saw palmetto extract causes indirect alpha1-adrenoceptor-mediated contractions via the release of noradrenaline from sympathetic neurons.
Cao
Nga
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Prostate Research Co-Operative, Faculty of Pharmacy, Monash University, Parkville, Victoria, Australia.
Haynes
John M
JM
Ventura
Sabatino
S
D000661:Amphetamine / Q000032:analysis; D000818:Animals; D003042:Cocaine / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D004558:Electric Stimulation; D006145:Guanethidine / Q000494:pharmacology; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D011224:Prazosin / Q000494:pharmacology; D011467:Prostate / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000032:analysis / Q000187:drug effects / Q000502:physiology; D028024:Serenoa / Q000737:chemistry; D013566:Sympathomimetics / Q000737:chemistry / Q000494:pharmacology*; D014439:Tyramine / Q000032:analysis; D001743:Urinary Bladder / Q000737:chemistry / Q000187:drug effects / Q000502:physiology; D014649:Vas Deferens / Q000737:chemistry / Q000187:drug effects / Q000502:physiology
D010936:Plant Extracts; D018340:Receptors, Adrenergic, alpha-1; D013566:Sympathomimetics; D000661:Amphetamine; D003042:Cocaine; D009543:Nifedipine; C040972:saw palmetto extract; D003891:Desipramine; D014439:Tyramine; D011224:Prazosin; D010646:Phentolamine; D006145:Guanethidine