MAMMALIAN REPRODUCTIVE CYCLE 



525 



was aceomi)lished with cither Dibonamine 

 or atropine. Neither agent, however, pre- 

 vented ovulation after injection of sheep 

 liypophyseal LH. A report by Hansel and 

 Trimberger (1951) stated that in cattle a 

 significant delay of ovulation (as great as 

 72 hours) followed atropine administration. 

 In control experiments the simultaneous 

 injection of atropine and human chorionic 

 gonadotrophin was followed by ovulation 

 slightly earlier than the normally expected 

 time. Treatments were begun 1 to 5 hours 

 after the onset of estrus. This work was con- 

 firmed and extended by Hough, Beardon 

 and Hansel (1955). In the hen, blockade of 

 ovulation, normal or induced by proges- 

 terone, has been reported after administra- 

 tion of Dibenamine, Dibenzyline, SKF-501 

 or atropine (Zarrow and Bastian, 1953; 

 van Tienhoven, 1955). According to van 

 Tienhoven, the drugs did not interfere with 

 the ovulating action of extrinsic gonado- 

 trophin. 



It is important that the same drugs will 

 block ovulation in lioth rabbits and rats 

 (Table 8.2) . Of ec^ual significance is the fact 

 that several agents that are ineffective in 

 rabbits are also ineffective in rats (notably 

 2-dibenzylaminoethanol, the imidazoline 

 adrenolytic drugs, and the ganglion blocking 

 agents). These considerations are inter- 

 jireted to mean that spontaneous ovulation 

 is invoked by neurohumoral mechanisms 

 that are very like those in the reflex ovula- 

 tion of rabbits. 



The suggestion that the l)locking effects 

 might result from nonspecific stress, causing 

 the hypophysis to be so actively secreting 

 ACTH that gonadotroiihin secretion is in- 

 terfered with (Dordoni and Timiras, 1952), 

 is clearly denied by several facts. ( 1 ) In 

 the rabbit studies, none of the various 

 agents prevented ovulation when injected 

 more than a minute post coitum. (2) In one 

 study (Sawyer, Markee and Everett, 1950b) 

 ovulation was actually induced by the intra- 

 venous injection of "lethal" doses of epi- 

 nephrine when the animals WTre protected 

 by atropine. (3) In rats ovulation is un- 

 affected by massive intravenous doses of 

 either the imidazoline drugs or 2-dibenzyl- 

 amionethanol in amounts known to be 

 stressing (Sawyer and Parkerson, 1953). 



TABLE 8.2 

 Pharmacologic Agents and Blockade of Ovulation 



Antiadrenergics 



/3-Haloalkylamines 



Dibenamine 



SKF-501 



Dibenzyline 



ImidazoHnes 



Priscoline 



Regitine 



Yohimbine 



Anticholinergics 



Atropine 



Banthine 



Antihistaminics 



Neo-antergan 



Ganglion blockers 



Tetraethvlammonium. . 



SC-1950/ 



Barbiturates 



Nembutal 



Dial 



Ipral 



Amvtal 



Barbital 



Phenobarl)ital 



Prominal 



Others 



Morphine 



Procaine, locally near 

 tuber 



Procaine, systemically . 



Chlorpromazine 



Reserpine 



Ether 



2,4-Dimtrophenol 



B3 



I Sawyer and associates, 1947-1951; Everett 

 and associates, 1949-1950; Christian, 1956; and see 

 present text. 



^ van Tienhoven, 1955; van Tienhoven, Nal- 

 bandov and Norton, 1954. 



3 Zarrow and Bastian, 1953. 



•• Fugo and Gross, 1942. 



5 Sulman and Black, 1945. 



^Hansel and Triml)erger, 1951; Hough, Bear- 

 don and Hansel, 1955. 



' Fraps and Case, 1953. 



* Doring and Goz, 1952. 



» Westman, 1947. 



1" Barraclough and Sawyer, 1955. 



II Westman and Jacol)8ohn, 1942. 

 1- Barraclough, 1956. 



13 Barraclough, 1955. 



" Unpublished. Temporary, during deep anes- 

 thesia. 



1^ Unpublished. EDso : 25 mg. per kg. subcu- 

 taneously. 



Key: B = Blockade. 



= No blockade. 



1 = Ovulation induced by the drug. 



