COMPARATIVE STUDIES OF EMESIS IN PIGEONS AND DOGS

¹ The Wellcome Research Laboratories, Tuckahoe , New York

Comparative studies of emesis were made in pigeons and dogs, using the emetic drugs, apomorphine, copper sulfate and piperazine hydrochloride, and the antiemetic drugs, cyclizine, atropine, scopolamine and chlorpromazine. In pigeons, vomiting occurred from the same compounds that were effective in dogs, but several marked differences appeared. The oral and intravenous doses of apomorphine were practically alike in pigeons, and the response from the oral route required nearly two hours. Oral copper sulfate in sufficient dosage (64 mgm./kgm.) was either emetic or else lethal. An intravenous dose of 6.4 mgm./kgm. of copper sulfate was emetic but not toxic for pigeons, though it was emetic and lethal for dogs. Data from both species are given on the emetic action of piperazine hydrochloride. Cyclizine at toxic levels (30 mgm./kgm., p.o.) becomes emetic for dogs, but in pigeons, cycizine, atropine and scopolamine were emetic with relatively few other symptoms, or none.

In the dog, oral doses of cyclizine prevented emesis from intravenous threshold doses of apomorphine or of piperazine hydrochloride and prevented or delayed emesis from oral thresholds of copper sulfate. Inhibition of oral copper sulfate required higher doses (30 mgm./kgm.) than did the other two drugs (10 and 5 mgm./kgm.). The blocks of apomorphine and copper sulfate suggest actions mediated through the chemoreceptor trigger zone and the vomiting center, respectively, but other types of interference in the emetic act are possible. In pigeons, oral cyclizine hastened emesis from oral apomorphine and oral piperazine and intensified the symptoms of the latter, but it decreased a compulsive feeding behavior due to apomorphine. Oral cyclizine appeared to delay and decrease emesis from oral copper sulfate and hastened death after the latter. The dosage data on pigeons provide a basis for work on the neural components of emesis.