AUTONOMIC PHARMACOLOGY OF THE CHICKEN WITH PARTICULAR REFERENCE TO ADRENERGIC BLOCKADE

¹ Department of Pharmacology, University of Utah College of Medicine, Salt Lake City, Utah

1. The chicken possesses adrenergic inhibitory mechanisms as evidenced by (a) vasodepression induced by isopropylnorepinephrine, and (b) vasomotor reversal following appropriate doses of Dibenzyline.

2. Large doses of the -haloalkylamine and ergot alkaloid adrenergic blocking agents are required to effect blockade in the chicken.

3. Dibenamine is capable of producing adrenergic blockade in the hen, but it is considerably less effective than Dibenzyline.

4. Dibenzyline can block sympathetic reflexes and sympathoadrenal discharge in addition to administered sympathomimetics.

5. The protective action of Dibenamine against the lethal effects of epinephrine was explored. Dibenamine protects against macroscopic pathological changes and death caused by epinephrine but does not influence immediate prostration.

6. Except for Hydergine and dihydroergocornine, no vasomotor reversals were brought about by ergot alkaloids alone; however, in combination with sub-effective doses of Dibenamine, ergotamine was able to induce a slight reversal.

7. In combination with Dibenamine, ergonovine manifested adrenergic blocking properties.

8. Dihydrogenated ergot alkaloids generally manifest pressor actions in the chicken; only rarely with Hydergine were depressor effects noted.

9. Angiotonin may be pressor or depressor in the chicken.

10. Dibenzyline reverses the pressor effects of angiotonin.

11. Other observations on the autonomic pharmacology and physiology of the chicken are reported and discussed.