Breast feeding increases vasoconstriction induced by electrical field stimulation in rat mesenteric artery. Role of neuronal nitric oxide and ATP.
OBJECTIVE
The aim of this study was to investigate in rat mesenteric artery whether breast feeding (BF) affects the vasomotor response induced by electrical field stimulation (EFS), participation by different innervations in the EFS-induced response and the mechanism/s underlying these possible modifications.


METHODS
Experiments were performed in female Sprague-Dawley rats (3 months old), divided into three groups: Control (in oestrous phase), mothers after 21 days of BF, and mothers that had recovered their oestral cycle (After BF, in oestrous phase). Vasomotor response to EFS, noradrenaline (NA) and nitric oxide (NO) donor DEA-NO were studied. Neuronal NO synthase (nNOS) and phosphorylated nNOS (P-nNOS) protein expression were analysed and NO, superoxide anion (O(2)(.-)), NA and ATP releases were also determined.


RESULTS
EFS-induced contraction was higher in the BF group, and was recovered after BF. 1 µmol/L phentolamine decreased the response to EFS similarly in control and BF rats. NA vasoconstriction and release were similar in both experimental groups. ATP release was higher in segments from BF rats. 0.1 mmol/L L-NAME increased the response to EFS in both control and BF rats, but more so in control animals. BF decreased NO release and did not modify O(2)(.-) production. Vasodilator response to DEA-NO was similar in both groups, while nNOS and P-nNOS expressions were decreased in segments from BF animals.


CONCLUSIONS
Breast feeding increases EFS-induced contraction in mesenteric arteries, mainly through the decrease of neuronal NO release mediated by decreased nNOS and P-nNOS expression. Sympathetic function is increased through the increased ATP release in BF rats.
Departamento de Fisiología, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, España.
Javier
J
Blanco-Rivero
Esther
E
Sastre
Laura
L
Caracuel
Miriam
M
Granado
Gloria
G
Balfagón
D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001942:Breast Feeding; D004558:Electric Stimulation; D005260:Female; D066298:In Vitro Techniques; D008638:Mesenteric Arteries / Q000294:innervation / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects
D018377:Neurotransmitter Agents; D009569:Nitric Oxide; D011189:Potassium Chloride; D000255:Adenosine Triphosphate; D000109:Acetylcholine