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Electrophysiological investigation of the projections of substance P neurons in the guinea-pig small intestine
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ELECTROPH¥SIOLOGICAL I N V E S T I G A T I O N OF THE P R O J E C T I O N S OF S U B S T A N C E P N E U R O N S IN THE G U I N E A - P I G S M A L L INTESTINE. T.K. 1
Smlth 1, J . B . F u r n e s s 1. M. Costa 2 and J.C.
Centre
Bornsteln 2
for N e u r o s c l e n c e and D e p a r t m e n t of A n a t o m y
&
University, Bedford Park, South A u s t r a l l a ~ llnders Centre for N e u r o s c l e n c e and D e p a r t m e n t of Physiology, University,
Bedford Park,
Histology, Fllnders
South A u s t r a l l a
I n t r a c e l l u l a r m i c r o e l e c t r o d e s were used to e x a m i n e the t r a n s m i s s i o n from excXtatory non-chollnerglc neurons that is blocked by substance P a n t a g o n i s t s in the c l r c u l a r muscle of the g u l n e a - p l g ileum. In order to a n a l y z e the p a t h w a y s of these neurons, nerve fibres in the m y e n t e r l c plexus were severed by c l r c u m f e r e n t l a l cuts and a l l o w e d 3-6 days to degenerate. In all e x p e r i m e n t s c h o l i n e r g l c and_ i n h i b i t o r y j u n c t i o n p Q t e n t l a l s were b l o c k e d with h y o s c l n e (5 x 10-7N) and a p a m i n (2 x 10-7N) r e s p e c t i v e l y ; g a n g l i o n i c t r a n s m i s s i o n was blocked with h e x a m e t h o n l u m (lO-~N) and contractions of the smooth muscle were inhibited with n t c a r d i p l n e (5 x lO-°N). Between lesions 1.5 - 4.5 mm apart, the e x c l t a t o r y junction potentials (EJP's) were of greater than normal a m p l l t u d e (up to 67 ~). As far as 11 mm oral to lesions there was a slight decrease in EJP amplitude (up to 20 ~) and on the anal side amplitudes were increased by up t o 50 • o v e r a b o u t 17 mm. Further experiments showed that the fibres project a b o u t 11 mm i n a circumferential direction, half of the c i r c u m f e r e n c e of the intestine. The o b s e r v a t i o n s s u g g e s t that the EJPs can be m o d i f i e d by transmitters released from other nerve fibres. Nevertheless, the results indicate that the m a j o r i t y of the p r o j e c t i o n s along the intestine of the n o n - c h o l l n e r g l c e x c i t a t o r y m o t o r n e u r o n s m e d i a t i n g these EJPs are short, that is, less than a b o u t 1.5 mm.
ELECTROPH¥SIOLOGICAL I N V E S T I G A T I O N OF THE P R O J E C T I O N S OF S U B S T A N C E P N E U R O N S IN THE G U I N E A - P I G S M A L L INTESTINE. T.K. 1
Smlth 1, J . B . F u r n e s s 1. M. Costa 2 and J.C.
Centre
Bornsteln 2
for N e u r o s c l e n c e and D e p a r t m e n t of A n a t o m y
&
University, Bedford Park, South A u s t r a l l a ~ llnders Centre for N e u r o s c l e n c e and D e p a r t m e n t of Physiology, University,
Bedford Park,
Histology, Fllnders
South A u s t r a l l a
I n t r a c e l l u l a r m i c r o e l e c t r o d e s were used to e x a m i n e the t r a n s m i s s i o n from excXtatory non-chollnerglc neurons that is blocked by substance P a n t a g o n i s t s in the c l r c u l a r muscle of the g u l n e a - p l g ileum. In order to a n a l y z e the p a t h w a y s of these neurons, nerve fibres in the m y e n t e r l c plexus were severed by c l r c u m f e r e n t l a l cuts and a l l o w e d 3-6 days to degenerate. In all e x p e r i m e n t s c h o l i n e r g l c and_ i n h i b i t o r y j u n c t i o n p Q t e n t l a l s were b l o c k e d with h y o s c l n e (5 x 10-7N) and a p a m i n (2 x 10-7N) r e s p e c t i v e l y ; g a n g l i o n i c t r a n s m i s s i o n was blocked with h e x a m e t h o n l u m (lO-~N) and contractions of the smooth muscle were inhibited with n t c a r d i p l n e (5 x lO-°N). Between lesions 1.5 - 4.5 mm apart, the e x c l t a t o r y junction potentials (EJP's) were of greater than normal a m p l l t u d e (up to 67 ~). As far as 11 mm oral to lesions there was a slight decrease in EJP amplitude (up to 20 ~) and on the anal side amplitudes were increased by up t o 50 • o v e r a b o u t 17 mm. Further experiments showed that the fibres project a b o u t 11 mm i n a circumferential direction, half of the c i r c u m f e r e n c e of the intestine. The o b s e r v a t i o n s s u g g e s t that the EJPs can be m o d i f i e d by transmitters released from other nerve fibres. Nevertheless, the results indicate that the m a j o r i t y of the p r o j e c t i o n s along the intestine of the n o n - c h o l l n e r g l c e x c i t a t o r y m o t o r n e u r o n s m e d i a t i n g these EJPs are short, that is, less than a b o u t 1.5 mm.