Thermolytic salivation, substance P and kinins in rats

In the heat, rats produce a large flow of saliva that they spread on their fur. We have tested whether substance P (SP) is involved in this response by using RP 67580, a NK1 tachykinin receptor antagonist, in normal and in kininogen-deficient rats. In anaesthetized rats, the sialogogic effect of SP (1 and 5 micrograms.kg-1 iv) was inhibited by RP 67580 (50 to 2500 micrograms.kg-1 iv). SP (5 micrograms.kg-1 iv) did not modify the vascular permeability to 125I-labelled albumin in submaxillary glands but increased this permeability in periglandular soft tissues and in the ears. This effect was suppressed by RP 67580 (50 to 2500 micrograms.kg-1 ip). Unanaesthetized normal male Wistar rats were exposed to ambient temperatures of 26 degrees C (thermoneutral range) or 36 degrees C for one hour. After this time period, a loss of body weight was observed. The thermolytic water loss reached 2% of body weight. This body weight loss was reduced by atropine (3 mg.kg-1 ip) or RP 67580 (50 to 2500 micrograms.kg-1 ip). The submaxillary glands were swollen and accumulated labelled albumin. This accumulation was reduced by atropine but was not affected by RP 67580. An extravasation of labelled albumin occurred in periglandular tissues. This accumulation was not modified by atropine which induced a large oedema of the soft tissues. Protein extravasation was suppressed by RP 67580 (2500 micrograms.kg-1) which did not modify or increased the volume of the oedema.(ABSTRACT TRUNCATED AT 250 WORDS)