15. 7. 1971 Specialia 799 concentration of 10 -~ g/m1 (Table II). In the 12- and 13-week-old foetuses, there were no changes in the action potential after carbamytcholine (10-L 10-~, 10-~). In the 14-week-old foetus there was a 21% decrease in the time for 90% repolarization (285 msec to 225 msec) after carbamylcholine (10-5). In the 16-week-old foetus there was no change in the time to 90% repolarisation at 10 -7, a 26.2% decrease at 10 -6 and a 49.6% decrease at 10 -5 (Figure 2). Contractions decreased by 10.5, 26.3 and 42.1% respectively in the preparation. A similar result was found in a 20-week-old foetus. No hyperpolarization was observed, as has been reported for adult human ~ and other species ~0. The adult human atria responds to acetylcholine in vitro by a shortening of the action potentialS, * as does the 7-day-old chick heart n. Ho~t*~_N and SUCKLING x~ suggested that the insensitivity of dog ventricular tissue to acetylcholine was related to the absence of nervous fibers in the ventricle. This hypothesis was supported by the insensitivity of the aneural heart of Myxine to acetylcholine ~3, ~,. In the rat foetus, sensitivity to aeetyl- choline occurs at about the eleventh ~ or thirteenth ~ day of gestation. Since innervation occurs in the rat heart between 14 and 16 days of gestation, sensitivity to acetylcholine appears to precede innervation. Our results show that carbamylcholine decreases the con- tractile response by about 50% with no effect on the action potential of the 12- and 13-week-old human foetal myocardium. This indicates that inotropie responses to exogenous cholinergic agents develop before electro- physiological responses. The contractile mechanism in the foetus is less sensitive to exogenousIy administered cholinergic agents than adult tissue from human a and other species 1°, as the foetal dose-response curve is shifted to the right. In addition, contractile responses were only decreased by 40-50% at 10 -s carbamylcholine in the foetal preparation, whereas contractions of adult atria from other species are abolished by even lower concentrations. Nerve cells and fibers have been found to be abundant in the 12-13-week-old human foetus~L In a t4-week-old foetus we found a limited electrophysio- logical response to carbamylcholine, an increased re- sponse was noted in a 16-week-old foetus with no further change in a foetus of 20 weeks. Hence, we conclude that electrophysiological responses of the human foetal myocardium to eholinergic agents are not developed until after innervation. A similar result has been reported for the effects of acetylcholine in the chick embryo 18,10. Rdsumd. Dons le coeur du foetus humain la r6ponse inotropique de la droge cholinergique ne se manifeste qu'apr~s le d6veloppement des fibres nerveuses. D. J. COLTART 20, B. A. SPILKER and S. J. MELDRUM Departments o/Cardiology and 2VIedical Electronics, St. Bartholomew's Hospital, London E.C. 1 (England), 31 December 1970. Table II. The negative inotropic effect of earbamylcholine on the human foetal atria Concentration Decrease of contraction amplitude (%) Left Right Double atrium • atriunl ~ atria ~ 10 -a 0 0 - 3 X 10-s 0 0 - 10 -v 15.8 16.7 6.0 3 × 10-~ 15.8 33.3 - 10 -6 38.6 41.6 23.5 3 X 10-s 47.4 50.0 - 8 × 10-s 47.4 50.0 - 10 -s 47.4 50.0 41.2 a "~he left atrium was electrically stimulated at 120/rain. ~ The fight atrium was spontaneously beating at 210/rain. No change in heart rate was observed at any concentration. The right and left atria were from different foetuses. ~ The 2 double atrial preparations were electrically driven at 10% above their spontaneous rates. n E. FINGL, L. A. WO09BOR¥ and H. H. HEEHT, J, Pharmac. exp. Ther. 10d, 103 (1952), is B. F. HOFFMASr and E. E. SUCKLinG, Am. J. Physiol. 173, 312 (1953). is E. OSTLOND, Aeta physiol, seand. 31 (Suppl. 112) 1 (1954). ~ K. B. Au~UST~NSSOU, R. FAYGE and A. JoHsELs, J. Physiol., Loud. 131,257 (I956). x~ E. K. HALL, Anat. Rec. ll8, 305 (1954). ** J. PAGER, C. BERNARD and M. GARGOUIL, C. r. SoP. Biol., Paris 159, 2470 (1965). 1~ W. E. GAE~E~ and S. E. TowssE~D, Am. J. Physiol. 152, 219 (1948). 18 j. W. PICKERING, J. Physiol. 20, 165 (1896). x9 Acknowledgments. We are grateful to Mr. D. FRASER and the Department of Obstetrics and Gynaecology for encouragement and supply of the surgical specimens and to Dr. J. HAMER for his guidance. We would also like to thank J. COBB for technical assistance. so Dr. COLTARX iS the Mary Schlarieb Research Scholar of the University of London 1970171 and the Cooper and Coventson Research Scholar of St. Bartholomew's Hospital 1970171. Functional Reinnervation of Cat Sympathetic Ganglia with Splenic Nerve Homografts Synoptic transmission in sympathetic ganglia is me- diated by acetylcholine x. The adrenergic structures in sympathetic ganglia might participate by inhibiting this cholinergic transmission °-. Several findings supporting such a role 3 have led to the theory of an adrenergic modulating system in ganglia 4. Additional support for this theory is the presence of noradrenaline (NA) con- taining nerve terminals in sympathetic ganglia; these have been postulated to be derived from interneurons ~ or to represent adrenergic collaterals, e. This morphological arrangement precludes the possibility of selectively stimulating these fibers outside the ganglion. The intraganglionic effects of the adrenergic axons could be analyzed more directly by surgically providing a sympathetic ganglion with a direct input of NA con- taining fibers. By cutting the sympathetic chain of the cat between the lumbar 3 (L3) and lumbar 4 (L4) ganglion and suturing the splenic nerve to the proximal stump (L,) we have surgically produced such a sympathetic ganglion. This report describes the electrophysiological results obtained by directly stimulating the noradrenaline containing fibers, One year after the surgery the L 4 ganglion together with its splenic nerve attachment and distal segment of