Effects of intravenous calcitonin gene-related peptide (CGRP) on local blood flow in the cat

• The effects of i.v. calcitonin gene-related peptide (CGRP) on regional blood flow, vascular resistance, heart rate and cardiac output in cats were studied using the microsphere method. Three series of experiments were performed. In the first there was no pre-treatment of the animals. In the second the animals were pre-treated with indomethacin (5 mg kg-1) in order to prevent the formation of prostaglandins. In the third series the ganglionic blocking agent hexamethonium bromide (80 mg kg-1) was given in order to prevent autonomic reflexes. CGRP was given as an i.v. infusion. Two doses were tested in each series. Animals with no pre-treatment and those pre-treated with indomethacin received first 60 pmol kg-1 infused over a 5-min period and then 180 pmol kg-1 infused over a 3-min period. Animals under ganglionic blockade received the same dose as the total infusions in the other series (240 pmol kg-1) infused over 4 min and a second infusion of 1.2 nmol kg-1 over 5 min. Vasodilatory effects were observed in most of the tissues tested, but there were marked differences in sensitivity. The most sensitive tissues seemed to be the lacrimal, submandibular and parotid glands, the nictitating membrane, the tongue and the gallbladder. The patterns of sensitivity were similar in all the series, indicating that neither prostaglandins nor autonomic reflexes were involved in the effects. In experiments with animals under ganglionic blockade, an increase in blood pressure, concomitant with an increase in heart rate, was seen 5 min after the infusions ended. Thus, it is likely that the peptide exerts a direct positive chronotropic effect on the feline heart.

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MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Annan klinisk medicin (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Other Clinical Medicine (hsv//eng)

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