Functional development of the emetic apparatus in the cat

Abstract

A series of cats and kittens varying in body weight from 150 gm (about 2 days of age) to over 3 kg (adult) were tested for the emetic response with graded doses of lanatoside C (.06–.8 mg/kg) and total body x-irradiation (12,000 r). At .06 mg/kg lanatoside C, the incidence of vomiting decreased from 52% in the adult group to zero in the 400-gm animals. At .08 and .12 mg/kg all the adult animals responded, but the incidence dropped to zero in the 250-gm group (about 10 days of age). At .3 and .8 mg/kg the incidence dropped from 100% in adults to zero in the 150-gm group. With total body x-irradiation at a maximum dose of 12,000 r the incidence was 100% in all groups between 400 gm and the adults, dropped to 50% in the 250-gm animals and to zero in the 150-gm group. It is thus clear that the period between the 150-gm and 250-gm stages is the critical period in the development of the emetic mechanism for the two stimuli employed in this study. The very low (about 6%) incidence of retching in animals of the younger groups which did not vomit suggests that the various components of the mechanism mature almost simultaneously.