MedWire News: Study results indicate that the increases in skin blood flow during postmenopausal hot flashes are mediated by neural pathways and can be eased with an injection of botulinium toxin A (BTX).

Introduction of BTX before a hot flash blocked or substantially inhibited the usual increase in cutaneous vascular conductance, reports the research team.

"These findings strongly indicate that increases in skin blood flow during the postmenopausal hot flash are neurally mediated via the same, or related, mechanisms as cutaneous vasodilation and sweating, necessary for thermoregulation in heat-stressed individuals," say Craig Crandall (Presbyterian Hospital of Dallas, Texas, USA) and colleagues.

The researchers measured skin blood flow responses at the forearm and glabellar skin and recorded postganglionic skin sympathetic neural activity (SSNA) before, during, and after hot flashes in 19 postmenopausal women,.

After an injection of BTX-to block the release of neurotransmitters from sympathetic cholinergic nerves-cutaneous vascular conductance was "greatly attenuated relative to the untreated sites," report Crandall et al.

SSNA increased by approximately four times during hot flashes, adds the team, and was accompanied by increases in sweat rate from 0.11 to 0.16 mg/cm^-2 per minute.

"These data demonstrate that the increase in skin blood flow during the postmenopausal hot flash is predominantly a neurally mediated event and is thus unlikely to be caused by nonneural mechanisms as previously suggested," conclude the researchers.

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