[Acute effects of topical application of methyl N-trimethyl-gamma-aminobutyrate chloride on cutaneous microcirculation in the healthy male rabbit].

Effects of acetylcholine (ACh) and its reversed carboxy analogue, methyl N-trimethyl-gamma-aminobutyrate chloride (MTB), induced either by topical application to the skin surface around a transparent round table chamber (REC) that had been previously installed to the ear lobe or by intravenous injection on the micro- and macrocirculations were studied in the healthy male rabbit. The effects of both drugs on the cutaneous microcirculation within the REC were observed vital-microscopically under conscious conditions and the microcirculatory events were visualized with a microscope-closed TV system and microphotoelectric plethysmography. The results were as follows: (1) Topical application of 1% MTB cream caused an enhanced perfusion of rhythmic microvascular blood due to vasomotion for a period of 30 min or longer, while ACh did so to a much less extent, if any. On the other hand, no appreciable change developed in any systemic hemodynamic parameters. (2) Intravenous administration of MTB or ACh caused a very transient dilator effect on micro-and macrocirculatory blood vessels according to its cholinergic stimulation, which could be blocked by atropinization. Almost the same efficacy on vasomotion was observed for each drug. (3) These findings indicate that the topical application of MTB to the skin surface may cause a physiologically acceptable vasodilation accompanied by vasomotion, and it would facilitate the oxygen diffusion by the follicular circulation.