15.4. 1977
Specialia
h a d 2 small a p e r t u r e s , one used to a c c o m m o d a t e t h e p o l y v i n y l plastic t u b i n g b y w h i c h t h e gas m i x t u r e s were delivered, t h e o t h e r used to pass t h e E C G leads f r o m t h e a n i m a l to t h e p o l y g r a p h a n d to allow for c o n t i n u o u s flushing a n d e x c h a n g e of gases. Gas was allowed to flow a t 4 l/rain, p e r m i t t i n g c o m p l e t e e q u i l i b r a t i o n of t h e gas in t h e b o x w i t h i n 1 m i n of s w i t c h i n g t o a n e w gas m i x t u r e . Oxyg e n c o n t e n t of t h e gas m i x t u r e , d e l i v e r e d f r o m c y l i n d e r s of O2 a n d N2 b y a n a d j u s t a b l e m u l t i p l e flow meter, was c o n t i n u o u s l y m o n i t o r e d b y a B e c k m a n m o d e l E2 O x y g e n A n a l y z e r , allowing c o n t r o l of t h e 02 c o n c e n t r a t i o n to w i t h i n 0.5%. Initially, c o m p r e s s e d air was allowed to flow for a t l e a s t 15 m i n to p e r m i t a t t a i n m e n t of a steady, b a s a l H R . A t t h e desired time, d e l i v e r y of t h e e x p e r i m e n t a l gas was s t a r t e d a n d m a i n t a i n e d a t 21% (20.6 • 0.5%) 02 for a 15 m i n c o n t r o l period, t h e n c h a n g e d t o 10.0 • 0.5% 02 for 5 min, a n d finally r e t u r n e d to 2 1 % 02 for a 10 m i n r e c o v e r y period. T h r o u g h o u t , H R was s a m p l e d a t i/2m i n - i n t e r v a l s . To t e s t t h e effects of b l o c k i n g drugs, e i t h e r 0.5 m l 0.9% NaC1 alone, or 0.2 m g a t r o p i n e sulfate or 5.0 m g p r o p r a n o l o l h y d r o c h l o r i d e (Inderal, Ayerst) diss o l v e d in 0.5 m l 0.9% NaC1, was i n j e c t e d i.p. A n i m a l s were t h e n placed in t h e boxes and, a f t e r 15 m i n to allow s t a b i l i z a t i o n of H R , t h e 15 m i n c o n t r o l p e r i o d w i t h 2 1 % 02 was b e g u n . (In p r e l i m i n a r y tests, 0.2 m g a t r o p i n e b l o c k e d for a t l e a s t 1 h t h e b r a d y c a r d i a p r o d u c e d in a p e n t o b a r b i t a l - a n e s t h e t i z e d 400 g r a t b y s t i m u l a t i o n of t h e r i g h t v a g u s w i t h s q u a r e w a v e i m p u l s e s a t 15 Hz, 2 msec d u r a t i o n , 8 V. 5.0 m g p r o p r a n o l o l blocked t h e t a c h y c a r d i c effect of 0.125 btg i s o p r o t e r e n o l [Isuprel, W i n t h r o p ] g i v e n i.v.) T h e o r d e r of a d m i n i s t r a t i o n of d r u g s was r a n d o m i z e d a m o n g t h e a n i m a l s , a n d a n i n t e r v a l of a t l e a s t 2 d a y s was allowed b e t w e e n d r u g t r i a l s o n e a c h a n i m a l . 24 trials of h y p o x i a were c o n d u c t e d on t h e u n t r e a t e d rats, i.e. 5 trials on e a c h of 4 animals, 4 t r i a l s on one. I n addition, 5 trials on e a c h of t h e 5 a n i n m l s were c o n d u c t e t w i t h 0.9% NaC1 injection, a n d 4 trials p e r a n i m a l were m a d e w i t h e a c h of t h e b l o c k i n g drugs. A n a l y s i s of v a r i a n c e of t h e d a t a o b t a i n e d d u r i n g c o n t r o l periods i n d i c a t e d t h a t t h e v a r i a n c e s a m o n g a n i m a l s were n o t significant, i.e. p > 0.25. Hence, H R s m e a s u r e d in t h e 20-25 t r i a l s for e a c h s a m p l e p o i n t , i.e. a t e a c h x/2-min-interval, were pooled a n d r e p o r t e d as a m e a n v a l u e for t h a t p o i n t plus or m i n u s t h e s t a n d a r d e r r o r of t h e m e a n . Results (figure). I n t h e u n t r e a t e d rats, H R a v e r a g e d 330 b e a t s p e r m i n (bpm) d u r i n g t h e l a t t e r p a r t of t h e c o n t r o l p e r i o d (21% 02). H R b e g a n to rise w i t h i n 1/2 m i n f r o m t h e o n s e t of a d m i n i s t r a t i o n of 10% 0 2, a n d a t t a i n e d a m a x i -
477
m u m , s t e a d y level a r o u n d 415 b p m a t a b o u t 3 rain. O n res u m p t i o n of 2 1 % 02, H R fell t o its c o n t r o l level w i t h i n 3 min. I n j e c t i o n of saline i n c r e a s e d r e s t i n g H R b y 10-15 b p m , b u t d i d n o t affect t h e p a t t e r n of r e s p o n s e t o h y p o x i a . F r o m a level of 340 b p m , H R rose s t e a d i l y t o a p e a k of 420 b p m a f t e r 3 m i n of e x p o s u r e to 10% 02. W h e n 1 0 % 02 was r e p l a c e d b y 2 1 % 02, H R r e t u r n e d to its r e s t i n g level in a b o u t 3 min. A t r o p i n e raised t h e r e s t i n g H R t o 420-440 b p m . H R i n c r e a s e d s t e a d i l y in r e s p o n s e to 10% 02, p e a k i n g a f t e r 3 m i n a t 470-480 b p m . W h e n 2 1 % 02 was r e s u m e d HIR d e c r e a s e d to its p r e v i o u s r e s t i n g level in a b o u t 2 min. I t t h e n c o n t i n u e d to decrease slightly, s t a b i l i z i n g a t 390-410 b p m . P r o p r a n o l o l lowered r e s t i n g H R to a p p r o x i m a t e l y 300 b p m a n d g r e a t l y m o d i f i e d t h e r e s p o n s e t o 1 0 % 02. H R rose t r a n s i e n t l y b y 15 b p m for t h e first 1 2 m i n of exposure, t h e n decreased g r a d u a l l y to its r e s t i n g level w h e r e it r e m a i n e d . O n r e s u m p t i o n of 2 1 % 02 H R fell to a b o u t 270 b p m in t h e first m i n u t e ; i t t h e n gradually increased and stabilized at the previous resting level. Discussion. T h e f a c t t h a t a t r o p i n e m a r k e d l y raised t h e r e s t i n g h e a r t r a t e (HR) implies a fairly h i g h degree of v a g a l t o n e in t h e n o r m a l r e s t i n g animal. T h e r e d u c t i o n in t h e a b s o l u t e m a g n i t u d e of t a c h y c a r d i a in r e s p o n s e to h y p o x i a ( m a x i m u m m e a n increase of 60 b p m w i t h a t r o pine vs. 80 b p m w i t h saline) p r o b a b l y i n d i c a t e s t h a t , s t a r t i n g f r o m a g r e a t l y e l e v a t e d level, H R was a p p r o a c h ing a n u p p e r l i m i t w h e n it i n c r e a s e d to 480 b p m in response to h y p o x i a . T h e failure of a t r o p i n e to a l t e r q u a l i t a tively the hypoxic tachycardia strongly indicates that i n h i b i t i o n of v a g a l t o n e p l a y s little role in t h e response. T h e decrease in r e s t i n g H R following i n j e c t i o n of prop r a n o l o l suggests some b e t a - a d r e n e r g i c c o n t r o l of t h e h e a r t in t h e n o r m a l r e s t i n g r a t . Since p r o p r a n o l o l essent i a l l y b l o c k e d t h e h y p o x i c t a c h y c a r d i a , t h i s r e s p o n s e is a p p a r e n t l y d u e a l m o s t e n t i r e l y to b e t a - a d r e n e r g i c s t i m u l a t i o n (cardiac s y m p a t h e t i c i n n e r v a t i o n a n d c i r c u l a t i n g c a t e c h o l a m i n e s ) . T h e t r a n s i e n c y of t h e slight t a c h y c a r d i a a t t h e b e g i n n i n g of t h e p e r i o d of h y p o x i a suggests t h a t it differs f r o m t h e n o r m a l t a c h y c a r d i c response. As t h i s slight rise in H R d i s a p p e a r e d d u r i n g c o n t i n u e d e x p o s u r e to 10% 02 , t h e p o s s i b i l i t y of i n c o m p l e t e b l o c k of t h e a d r e n e r g i c r e c e p t o r s b y t h e p r o p r a n o l o l is unlikely. No r e a d y e x p l a n a t i o n for t h e p o s t - h y p o x i c b r a d y c a r d i a in t h e p r o p r a n o l o l - t r e a t e d a n i m a l s is a t h a n d , b u t m e d i a t i o n of t h e b r a d y c a r d i a b y a b a r o r e c e p t o r reflex m a y b e r u l e d o u t since p r e l i m i n a r y u n p u b l i s h e d o b s e r v a t i o n s i n d i c a t e t h a t a r t e r i a l p r e s s u r e does n o t rise in r e s p o n s e t o h y p o x i a in u n t r e a t e d or p r o p r a n o l o l - b l o c k e d rats.
S u s t a i n e d a n d t r a n s i e n t c o r t i c a l n e u r o n e s i n a r e a 18 of t h e c a t S. Y a m a n e , T. N i k a r a l a n d N. Sugie
Bionics Research Section, Electrotechnical Laboratory, Nagatacho, Chiyodaku, Tokyo (Japan), 7 October 7976 Summary. T h e m a j o r i t y of t h e simple cells in a r e a 18 of t h e c a t ' s v i s u a l c o r t e x g a v e p u r e t r a n s i e n t responses to f l a s h i n g slits of light. A few simple cells g a v e s u s t a i n e d r e s p o n s e s to s t a t i o n a r y slits of light. All of t h e c o m p l e x cells e n c o u n t e r e d g a v e t r a n s i e n t responses. N e u r o p h y s i o l o g i c a l i n v e s t i g a t i o n s of t h e r e c e p t i v e field p r o p e r t i e s of t h e r e l a y ceils i n t h e l a t e r a l g e n i c u l a t e n u c l e u s (LGN) of t h e c a t h a v e r e v e a l e d 2 m a j o r g r o u p s of cells, X or ' s u s t a i n e d ' a n d Y or ' t r a n s i e n t ' cells 2-~. I k e d a a n d W r i g h t 6 h a v e classified cells in area 17 of t h e v i s u a l c o r t e x as ' s u s t a i n e d ' or ' t r a n s i e n t ' a n d r e p o r t e d t h a t t h e ' s u s t a i n e d / t r a n s i e n t ' classification is i n d e p e n d e n t of t h e ' s i m p l e / c o m p l e x ' classification.
1 2 3 4 5 6
Present address: Department of Physiology, Iwate Medical University, Morioka, Japan. B.G. Cleland, M. W. Dubin and W. R. Levieck, J. Physiol., Lond. 217, 473 (1971). K.-P. Hoffman and J. Stone, Brain Res. 32, 460 (1971). K.-P. Hoffman, J. Stone and S. M. Sherman, J. Neurophysiol. 35, 518 (1972). J. Stone and B. Dreher, J. Neurophysiol. 36, 551 (1973). H. Ikeda and M. J. Wright, Exp. Brain Res. 22, 363 (1975).
478
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I t is well e s t a b l i s h e d t h a t t h e p e r i s t r i a t e a r e a 18 r e c e i v e s a d i r e c t i n p u t f r o m t h e L G N ~ 14. A t l e a s t t h e m a j o r i t y of t h e s i m p l e a n d c o m p l e x ceils in a r e a 18 w e r e m o n o s y n a p t i c a l l y e x c i t e d b y e l e c t r i c a l s t i m u l a t i o n in t h e L G N 3,15,16. M o r e o v e r , t h e a x o n s r e a c h i n g a r e a 18 f r o m t h e L G ~ b e l o n g e x c l u s i v e l y t o Y-cells 5, 16. T h e r e f o r e , it is e x p e c t e d t h a t t h e m a j o r i t y of t h e s i m p l e a n d c o m p l e x
A
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EXPERIENTIA 33/4
cells in a r e a 18 w o u l d be classified as ' t r a n s i e n t ' cells. T h e a i m of t h e p r e s e n t p a p e r is t o c h e c k t h e a b o v e p r e d i c t i o n . Material and methods. 12 a d u l t c a t s w e i g h i n g 2 . 5 - 3 . 5 k g w e r e u s e d . C a n n u l a t i o n s of t h e t r a c h e a a n d t h e r i g h t c e p h a l i c v e i n a n d c r a n i o t o m y Were p e r f o r m e d u n d e r fluothane (2.5-3.5%) anesthesia. Ears and woundlips w e r e l o c a l l y a n e s t h e t i z e d w i t h 1~ x y l o c a i n e . T o p r e v e n t
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Classification of cortical cells in area 18 into 3 types. Average response histograms were obtained from 'simple-transient' (S-T), 'simple-sustained' (S-S), and 'colnplex-transient' (C-T) cortical cells. Each histogram was obtained using a flashing stationary slit of light, optimally oriented and placed in the position indicated in the receptive field (RF) profile, and was collected over 20 presentations of the slit of light. Horizontal bar below each histogram: presentation of a slit of light for 5 see. Arrows: spontaneous firing rate. Slit dimensions: 15 ~ • 0.6 ~ in A, and 15 ~ • 1.5 ~ in B and C. Receptive field location from the vertical meridian and from the horizontal meridian: 14 ~ lateral and 20 ~ below in A, 20 ~ lateral arid 20 ~ below in B and 10 ~ lateral and 25 ~ below in C. Receptive field profiles were obtained from the responses to a slit of light. Ordinate: peak evoked response (spikes/s). Abscissa: distance across the receptive field at right angles to the prefered orientation. Open circles: on response. Filled circles: off-response.
15.4. 1977
Specialia
eye m o v e m e n t , t h e a n i m a l was p a r a l y z e d w i t h a cont i n u o u s perfusion of gallamine t r i e t h i o d i d e (6 m g / k g per h) a n d d - t u b o c u r a l i n e (1 m g / k g p e r h). T h e a n i m a l was artificially v e n t i l a t e d w i t h 70% N~O a n d 30% O~ w i t h a d d i t i o n a l f l u o t h a n e 0.5%. The b o d y t e m p e r a t u r e was m a i n t a i n e d a t 37-38~ b y a t h e r m o s t a t i c a l l y controlled h e a t i n g b l a n k e t . The a n i m a l was fixed in a B i s h o p t y p e s t e r e o t a x i c app a r a t u s facing a 114 c m t a n g e n t screen w i t h a l u m i n a n c e of a p p r o x i m a t e l y 10 c d / m 2. The pupils were d i l a t e d b y a p p l y i n g t r o p i c a m i d a n d p h e n y l e p h e r i n e chloride (Midorin, S a n t e n Chemical). A pair of c o n t a n t lenses were selected f r o m a f a m i l y of lenses p r e p a r e d in 1/s d i o p t e r steps, so t h a t t h e r e t i n a was focussed on t h e screen using direct p r o j e c t i o n m e t h o d 17. F r o m t h e p o s i t i o n of t h e b l i n d s p o t s p r o j e c t e d b y t h e m e t h o d , t h e area centralis of e a c h eye was m a r k e d on t h e screen using t h e d a t a of V a k k u r et al. is. A slit of light of a d j u s t a b l e d i m e n s i o n s a n d o r i e n t a t i o n was p r o j e c t e d on t h e screen. I t could be m o v e d b a c k a n d f o r t h b y a pair of m i r r o r s a t t a c h e d to m o v i n g coil g a l v a n o m e t e r s . A m e c h a n i c a l s h u t t e r , o p e r a t e d electrically, was e m p l o y e d for flashing t h e slit of light. The i n t e n s i t y of t h e slit of l i g h t w a s a b o u t 60 c d / m ~. Single u n i t s were r e c o r d e d e x t r a c e l l u l a r l y b y a glasscoated tungsten microelectrode inserted through the d u r a m a t t e r . The t r e p h i n e hole in t h e c r a n i u m was sealed w i t h soft b o n e w a x to m i n i m i z e b r a i n m o v e m e n t . Once a u n i t was isolated, its o p t i m a l o r i e n t a t i o n was d e t e r m i n e d using slits of light m o v e d in a d i r e c t i o n p e r p e n d i c u l a r to t h e slit's o r i e n t a t i o n . T h e r e a f t e r , a flashing slit of light, o r i e n t e d parallel to t h e r e c e p t i v e field o r i e n t a t i o n , was used for t h e stimulus. A v e r a g e r e s p o n s e h i s t o g r a m s (bin w i d t h = 10 ms) were o b t a i n e d over 20 p r e s e n t a t i o n s of this stimulus. The s p o n t a n e o u s firing of a u n i t was also collected w i t h b a c k g r o u n d i l l u m i n a t i o n alone. The average r e s p o n s e of t h e u n i t was c o m p a r e d w i t h t h e spont a n e o u s firing, in order to classify t h e u n i t as ' s u s t a i n e d ' or ' t r a n s i e n t ' . R e c e p t i v e fields were also classified as simple or c o m p l e x cells according to t h e criteria set b y H u b e l a n d Wiese119, 20 W e c o n s i d e r e d t h e r e f o r e as simple cells only t h o s e o r i e n t a t i o n specific units w h o s e r e c e p t i v e fields could be s u b d i v i d e d into s p a t i a l l y d i s t i n c t on- a n d off-areas, a n d whose responses were m a x i m a l w i t h stimuli filling an entire on- or off-area. W e c o n s i d e r e d as c o m p l e x cells t h o s e o r i e n t a t i o n specific cells w h i c h e i t h e r did n o t s h o w a s e p a r a t i o n of t h e r e c e p t i v e field into e x c i t a t o r y areas, or w h i c h did n o t s h o w s u m m a t i o n of t h e s t i m u l u s effect over such s e p a r a t e areas. Results a n d discussion. All u n i t s were r e c o r d e d f r o m an area w i t h i n H o r s l e y Clarke c o o r d i n a t e s a n t e r i o r 3-5 a n d lateral 4 5 m m , in o r d e r to a v o i d t h e b o r d e r b e t w e e n area 17 a n d 18. A n d also t o a v o i d recording f r o m t h e u p p e r b a n k of t h e s u p r a - s p l e n i a l sulcus, electrodes were a d v a n c e d up to 2 m m f r o m t h e cortical surface. Most u n i t s of t h e s a m p l e h a d t h e i r r e c e p t i v e fields l o c a t e d 7-20 ~ lateral f r o m t h e v e r t i c a l m e r i d i a n a n d 8-25 ~ below t h e h o r i z o n t a l meridian. W e h a v e always c h e c k e d u p on t h e m a t t e r t h a t r e c e p t i v e fields of u n i t s r e c o r d e d f r o m an area w i t h i n lateral 3 a n d a n t e r i o r 3-5 m m were l o c a t e d n e a r e r t o t h e v e r t i c a l m e r i d i a n t h a n t h o s e of t h e s a m p l e d units. The cells of the s a m p l e were a c t u a l l y r e g i s t r a t e d in area 18. W e o b s e r v e d 3 c h a r a c t e r i s t i c t y p e s of responses to flashing slits of light w i t h i n r e c e p t i v e fields. T h e s e are s h o w n in average r e s p o n s e h i s t o g r a m s of t h e figure, w i t h arrows to i n d i c a t e t h e m e a n s p o n t a n e o u s firing r a t e of t h e unit. The first t y p e of t h e u n i t is i l l u s t r a t e d b y t h e h i s t o g r a m s in t h e figure A. I t gave a t r a n s i e n t r e s p o n s e to a flashing slit of light. A f t e r t h e t r a n s i e n t response, t h e firing r a t e
479
i m m e d i a t e l y fell to t h e s p o n t a n e o u s level. T h e r e c e p t i v e field was s u b d i v i d e d into s p a t i a l l y d i s t i n c t on- a n d offareas. The second t y p e of t h e u n i t is i l l u s t r a t e d b y t h e histo-, g r a m s in t h e figure B. I t h a d a r e c e p t i v e field profile similar to t h e first t y p e . I t gave a s u s t a i n e d r e s p o n s e t o a slit of light w i t h i n on-area. The r e s p o n s e r e m a i n e d m o r e t h a n t 0 spikes/sec a b o v e t h e s p o n t a n e o u s r a t e a f t e r 5 sec. W i t h i n off-area, t h i s u n i t gave a t r a n s i e n t r e s p o n s e to off-stimulus of t h e slit of light. T h e t h i r d t y p e of t h e u n i t is i l i u s t r a t e d b y t h e h i s t o g r a m s in t h e figure, C. I t gave a t r a n s i e n t r e s p o n s e to b o t h ona n d o f f - s t i m u l i of a slit of l i g h t w i t h i n its r e c e p t i v e field. T h e first a n d second t y p e s were classified as simple ceils, a n d t h e t h i r d as c o m p l e x cells. Of 137 u n i t s e n c o u n t e r e d , 42 were simple cells, 73 were c o m p l e x cells, a n d t h e rem a i n i n g 22 cells were n o t classified in t h e s i m p l e / c o m p l e x s c h e m e either. Of 42 simple cells, 34 gave p u r e t r a n s i e n t r e s p o n s e s to f l a s h i n g slits of light, a n d o n l y 8 gave s u s t a i n e d r e s p o n s e s t o s t a t i o n a r y slits of light w i t h i n onarea. All of t h e c o m p l e x cells e n c o u n t e r e d gave t r a n s i e n t responses. Therefore, of simple a n d c o m p l e x cells in area 18, 93% were of t r a n s i e n t t y p e . I n c o n t r a s t to area 18, in area 17, 61% o u t of simple a n d c o m p l e x cells were t r a n s i e n t t y p e a n d s u s t a i n e d r e s p o n s e s were o b s e r v e d b o t h in t h e simple a n d c o m p l e x cells 21. Therefore, ' t r a n s i e n t ' cells were m u c h m o r e f r e q u e n t in area 18 t h a n in area 17. A n o t h e r difference was t h a t s u s t a i n e d r e s p o n s e s were n o t o b s e r v e d in t h e c o m p l e x cells e n c o u n t e r e d in area 18. The g r e a t m a j o r i t y of area 18 cells g a v e p u r e t r a n s i e n t responses. This is c o n s i s t e n t w i t h tile f a c t t h a t Y-cells c o n s t i t u t e t h e only i n p u t f r o m t h e L G N t o area 18. H o w ever, our d a t a h a v e s h o w n t h a t a few simple cells in a r e a 18 give s u s t a i n e d responses, w h i c h X-cells are likely t o give.
7 8 9 10 ll 12 13 14 15 16 17 18 19 20 21
L.J. Garey and T. P. S. Powell, Proc. R. Soc. 13 169, 107 (1967). L.J. Garey and T. P. S. Powell, Proe. R. Soc. B 179, 41 (1971). M. Glieekstein, R. A. King, J. A. Muller and M. Berkley, J. comp. Neurol. 130, 55 (1967). S.K. Niimi and J. M. Sprague, J. eomp. Neurol. 138, 219 (1970). A.C. Rosenquist, S. B. Edwards and L. A. Palmar, Brain Res. 80, 71 (1974). S. Rossignoll and M. Colonnier, Vision Res., suppl. 3, 329 (1971). K. Toyama, K. Matsunami, T. Ohno and S. Takashiki, Exp. Brain Res. 21, 45 (1974). M.S. Wilson and B. G. Cragg, J. Anat., Lond., 101,679 (1967). K. Toyama, K. Maekawa and T. Takeda, Brain Res. 61, 395 (1973). F. Tretter, M. Cynader and W. Singer, j. Neurophysiol. 38, 1099 (1975). S. Yamane, S. Kaji and N. Sugie, J. physiol. Soe. Japan 33, (1971>. G . J . Vakkur, P. O. Bishop and W. Kozak, Vision Res. 3, 289 (1963). D.H. Hubel and T. N. Wiesel, J. Physiol., Lond. 160, 106 (1962). D.H. Hubel and T. N. Wiesel, J. Neurophysiol. 28, 229 (1965). H. Ikeda and M. J. Wright, Exp. Brain Res. 22, 385 (1975).
Specialia
h a d 2 small a p e r t u r e s , one used to a c c o m m o d a t e t h e p o l y v i n y l plastic t u b i n g b y w h i c h t h e gas m i x t u r e s were delivered, t h e o t h e r used to pass t h e E C G leads f r o m t h e a n i m a l to t h e p o l y g r a p h a n d to allow for c o n t i n u o u s flushing a n d e x c h a n g e of gases. Gas was allowed to flow a t 4 l/rain, p e r m i t t i n g c o m p l e t e e q u i l i b r a t i o n of t h e gas in t h e b o x w i t h i n 1 m i n of s w i t c h i n g t o a n e w gas m i x t u r e . Oxyg e n c o n t e n t of t h e gas m i x t u r e , d e l i v e r e d f r o m c y l i n d e r s of O2 a n d N2 b y a n a d j u s t a b l e m u l t i p l e flow meter, was c o n t i n u o u s l y m o n i t o r e d b y a B e c k m a n m o d e l E2 O x y g e n A n a l y z e r , allowing c o n t r o l of t h e 02 c o n c e n t r a t i o n to w i t h i n 0.5%. Initially, c o m p r e s s e d air was allowed to flow for a t l e a s t 15 m i n to p e r m i t a t t a i n m e n t of a steady, b a s a l H R . A t t h e desired time, d e l i v e r y of t h e e x p e r i m e n t a l gas was s t a r t e d a n d m a i n t a i n e d a t 21% (20.6 • 0.5%) 02 for a 15 m i n c o n t r o l period, t h e n c h a n g e d t o 10.0 • 0.5% 02 for 5 min, a n d finally r e t u r n e d to 2 1 % 02 for a 10 m i n r e c o v e r y period. T h r o u g h o u t , H R was s a m p l e d a t i/2m i n - i n t e r v a l s . To t e s t t h e effects of b l o c k i n g drugs, e i t h e r 0.5 m l 0.9% NaC1 alone, or 0.2 m g a t r o p i n e sulfate or 5.0 m g p r o p r a n o l o l h y d r o c h l o r i d e (Inderal, Ayerst) diss o l v e d in 0.5 m l 0.9% NaC1, was i n j e c t e d i.p. A n i m a l s were t h e n placed in t h e boxes and, a f t e r 15 m i n to allow s t a b i l i z a t i o n of H R , t h e 15 m i n c o n t r o l p e r i o d w i t h 2 1 % 02 was b e g u n . (In p r e l i m i n a r y tests, 0.2 m g a t r o p i n e b l o c k e d for a t l e a s t 1 h t h e b r a d y c a r d i a p r o d u c e d in a p e n t o b a r b i t a l - a n e s t h e t i z e d 400 g r a t b y s t i m u l a t i o n of t h e r i g h t v a g u s w i t h s q u a r e w a v e i m p u l s e s a t 15 Hz, 2 msec d u r a t i o n , 8 V. 5.0 m g p r o p r a n o l o l blocked t h e t a c h y c a r d i c effect of 0.125 btg i s o p r o t e r e n o l [Isuprel, W i n t h r o p ] g i v e n i.v.) T h e o r d e r of a d m i n i s t r a t i o n of d r u g s was r a n d o m i z e d a m o n g t h e a n i m a l s , a n d a n i n t e r v a l of a t l e a s t 2 d a y s was allowed b e t w e e n d r u g t r i a l s o n e a c h a n i m a l . 24 trials of h y p o x i a were c o n d u c t e d on t h e u n t r e a t e d rats, i.e. 5 trials on e a c h of 4 animals, 4 t r i a l s on one. I n addition, 5 trials on e a c h of t h e 5 a n i n m l s were c o n d u c t e t w i t h 0.9% NaC1 injection, a n d 4 trials p e r a n i m a l were m a d e w i t h e a c h of t h e b l o c k i n g drugs. A n a l y s i s of v a r i a n c e of t h e d a t a o b t a i n e d d u r i n g c o n t r o l periods i n d i c a t e d t h a t t h e v a r i a n c e s a m o n g a n i m a l s were n o t significant, i.e. p > 0.25. Hence, H R s m e a s u r e d in t h e 20-25 t r i a l s for e a c h s a m p l e p o i n t , i.e. a t e a c h x/2-min-interval, were pooled a n d r e p o r t e d as a m e a n v a l u e for t h a t p o i n t plus or m i n u s t h e s t a n d a r d e r r o r of t h e m e a n . Results (figure). I n t h e u n t r e a t e d rats, H R a v e r a g e d 330 b e a t s p e r m i n (bpm) d u r i n g t h e l a t t e r p a r t of t h e c o n t r o l p e r i o d (21% 02). H R b e g a n to rise w i t h i n 1/2 m i n f r o m t h e o n s e t of a d m i n i s t r a t i o n of 10% 0 2, a n d a t t a i n e d a m a x i -
477
m u m , s t e a d y level a r o u n d 415 b p m a t a b o u t 3 rain. O n res u m p t i o n of 2 1 % 02, H R fell t o its c o n t r o l level w i t h i n 3 min. I n j e c t i o n of saline i n c r e a s e d r e s t i n g H R b y 10-15 b p m , b u t d i d n o t affect t h e p a t t e r n of r e s p o n s e t o h y p o x i a . F r o m a level of 340 b p m , H R rose s t e a d i l y t o a p e a k of 420 b p m a f t e r 3 m i n of e x p o s u r e to 10% 02. W h e n 1 0 % 02 was r e p l a c e d b y 2 1 % 02, H R r e t u r n e d to its r e s t i n g level in a b o u t 3 min. A t r o p i n e raised t h e r e s t i n g H R t o 420-440 b p m . H R i n c r e a s e d s t e a d i l y in r e s p o n s e to 10% 02, p e a k i n g a f t e r 3 m i n a t 470-480 b p m . W h e n 2 1 % 02 was r e s u m e d HIR d e c r e a s e d to its p r e v i o u s r e s t i n g level in a b o u t 2 min. I t t h e n c o n t i n u e d to decrease slightly, s t a b i l i z i n g a t 390-410 b p m . P r o p r a n o l o l lowered r e s t i n g H R to a p p r o x i m a t e l y 300 b p m a n d g r e a t l y m o d i f i e d t h e r e s p o n s e t o 1 0 % 02. H R rose t r a n s i e n t l y b y 15 b p m for t h e first 1 2 m i n of exposure, t h e n decreased g r a d u a l l y to its r e s t i n g level w h e r e it r e m a i n e d . O n r e s u m p t i o n of 2 1 % 02 H R fell to a b o u t 270 b p m in t h e first m i n u t e ; i t t h e n gradually increased and stabilized at the previous resting level. Discussion. T h e f a c t t h a t a t r o p i n e m a r k e d l y raised t h e r e s t i n g h e a r t r a t e (HR) implies a fairly h i g h degree of v a g a l t o n e in t h e n o r m a l r e s t i n g animal. T h e r e d u c t i o n in t h e a b s o l u t e m a g n i t u d e of t a c h y c a r d i a in r e s p o n s e to h y p o x i a ( m a x i m u m m e a n increase of 60 b p m w i t h a t r o pine vs. 80 b p m w i t h saline) p r o b a b l y i n d i c a t e s t h a t , s t a r t i n g f r o m a g r e a t l y e l e v a t e d level, H R was a p p r o a c h ing a n u p p e r l i m i t w h e n it i n c r e a s e d to 480 b p m in response to h y p o x i a . T h e failure of a t r o p i n e to a l t e r q u a l i t a tively the hypoxic tachycardia strongly indicates that i n h i b i t i o n of v a g a l t o n e p l a y s little role in t h e response. T h e decrease in r e s t i n g H R following i n j e c t i o n of prop r a n o l o l suggests some b e t a - a d r e n e r g i c c o n t r o l of t h e h e a r t in t h e n o r m a l r e s t i n g r a t . Since p r o p r a n o l o l essent i a l l y b l o c k e d t h e h y p o x i c t a c h y c a r d i a , t h i s r e s p o n s e is a p p a r e n t l y d u e a l m o s t e n t i r e l y to b e t a - a d r e n e r g i c s t i m u l a t i o n (cardiac s y m p a t h e t i c i n n e r v a t i o n a n d c i r c u l a t i n g c a t e c h o l a m i n e s ) . T h e t r a n s i e n c y of t h e slight t a c h y c a r d i a a t t h e b e g i n n i n g of t h e p e r i o d of h y p o x i a suggests t h a t it differs f r o m t h e n o r m a l t a c h y c a r d i c response. As t h i s slight rise in H R d i s a p p e a r e d d u r i n g c o n t i n u e d e x p o s u r e to 10% 02 , t h e p o s s i b i l i t y of i n c o m p l e t e b l o c k of t h e a d r e n e r g i c r e c e p t o r s b y t h e p r o p r a n o l o l is unlikely. No r e a d y e x p l a n a t i o n for t h e p o s t - h y p o x i c b r a d y c a r d i a in t h e p r o p r a n o l o l - t r e a t e d a n i m a l s is a t h a n d , b u t m e d i a t i o n of t h e b r a d y c a r d i a b y a b a r o r e c e p t o r reflex m a y b e r u l e d o u t since p r e l i m i n a r y u n p u b l i s h e d o b s e r v a t i o n s i n d i c a t e t h a t a r t e r i a l p r e s s u r e does n o t rise in r e s p o n s e t o h y p o x i a in u n t r e a t e d or p r o p r a n o l o l - b l o c k e d rats.
S u s t a i n e d a n d t r a n s i e n t c o r t i c a l n e u r o n e s i n a r e a 18 of t h e c a t S. Y a m a n e , T. N i k a r a l a n d N. Sugie
Bionics Research Section, Electrotechnical Laboratory, Nagatacho, Chiyodaku, Tokyo (Japan), 7 October 7976 Summary. T h e m a j o r i t y of t h e simple cells in a r e a 18 of t h e c a t ' s v i s u a l c o r t e x g a v e p u r e t r a n s i e n t responses to f l a s h i n g slits of light. A few simple cells g a v e s u s t a i n e d r e s p o n s e s to s t a t i o n a r y slits of light. All of t h e c o m p l e x cells e n c o u n t e r e d g a v e t r a n s i e n t responses. N e u r o p h y s i o l o g i c a l i n v e s t i g a t i o n s of t h e r e c e p t i v e field p r o p e r t i e s of t h e r e l a y ceils i n t h e l a t e r a l g e n i c u l a t e n u c l e u s (LGN) of t h e c a t h a v e r e v e a l e d 2 m a j o r g r o u p s of cells, X or ' s u s t a i n e d ' a n d Y or ' t r a n s i e n t ' cells 2-~. I k e d a a n d W r i g h t 6 h a v e classified cells in area 17 of t h e v i s u a l c o r t e x as ' s u s t a i n e d ' or ' t r a n s i e n t ' a n d r e p o r t e d t h a t t h e ' s u s t a i n e d / t r a n s i e n t ' classification is i n d e p e n d e n t of t h e ' s i m p l e / c o m p l e x ' classification.
1 2 3 4 5 6
Present address: Department of Physiology, Iwate Medical University, Morioka, Japan. B.G. Cleland, M. W. Dubin and W. R. Levieck, J. Physiol., Lond. 217, 473 (1971). K.-P. Hoffman and J. Stone, Brain Res. 32, 460 (1971). K.-P. Hoffman, J. Stone and S. M. Sherman, J. Neurophysiol. 35, 518 (1972). J. Stone and B. Dreher, J. Neurophysiol. 36, 551 (1973). H. Ikeda and M. J. Wright, Exp. Brain Res. 22, 363 (1975).
478
Specialia
I t is well e s t a b l i s h e d t h a t t h e p e r i s t r i a t e a r e a 18 r e c e i v e s a d i r e c t i n p u t f r o m t h e L G N ~ 14. A t l e a s t t h e m a j o r i t y of t h e s i m p l e a n d c o m p l e x ceils in a r e a 18 w e r e m o n o s y n a p t i c a l l y e x c i t e d b y e l e c t r i c a l s t i m u l a t i o n in t h e L G N 3,15,16. M o r e o v e r , t h e a x o n s r e a c h i n g a r e a 18 f r o m t h e L G ~ b e l o n g e x c l u s i v e l y t o Y-cells 5, 16. T h e r e f o r e , it is e x p e c t e d t h a t t h e m a j o r i t y of t h e s i m p l e a n d c o m p l e x
A
RF ]~ PROFILE /
S-T
EXPERIENTIA 33/4
cells in a r e a 18 w o u l d be classified as ' t r a n s i e n t ' cells. T h e a i m of t h e p r e s e n t p a p e r is t o c h e c k t h e a b o v e p r e d i c t i o n . Material and methods. 12 a d u l t c a t s w e i g h i n g 2 . 5 - 3 . 5 k g w e r e u s e d . C a n n u l a t i o n s of t h e t r a c h e a a n d t h e r i g h t c e p h a l i c v e i n a n d c r a n i o t o m y Were p e r f o r m e d u n d e r fluothane (2.5-3.5%) anesthesia. Ears and woundlips w e r e l o c a l l y a n e s t h e t i z e d w i t h 1~ x y l o c a i n e . T o p r e v e n t
3, " "~
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Classification of cortical cells in area 18 into 3 types. Average response histograms were obtained from 'simple-transient' (S-T), 'simple-sustained' (S-S), and 'colnplex-transient' (C-T) cortical cells. Each histogram was obtained using a flashing stationary slit of light, optimally oriented and placed in the position indicated in the receptive field (RF) profile, and was collected over 20 presentations of the slit of light. Horizontal bar below each histogram: presentation of a slit of light for 5 see. Arrows: spontaneous firing rate. Slit dimensions: 15 ~ • 0.6 ~ in A, and 15 ~ • 1.5 ~ in B and C. Receptive field location from the vertical meridian and from the horizontal meridian: 14 ~ lateral and 20 ~ below in A, 20 ~ lateral arid 20 ~ below in B and 10 ~ lateral and 25 ~ below in C. Receptive field profiles were obtained from the responses to a slit of light. Ordinate: peak evoked response (spikes/s). Abscissa: distance across the receptive field at right angles to the prefered orientation. Open circles: on response. Filled circles: off-response.
15.4. 1977
Specialia
eye m o v e m e n t , t h e a n i m a l was p a r a l y z e d w i t h a cont i n u o u s perfusion of gallamine t r i e t h i o d i d e (6 m g / k g per h) a n d d - t u b o c u r a l i n e (1 m g / k g p e r h). T h e a n i m a l was artificially v e n t i l a t e d w i t h 70% N~O a n d 30% O~ w i t h a d d i t i o n a l f l u o t h a n e 0.5%. The b o d y t e m p e r a t u r e was m a i n t a i n e d a t 37-38~ b y a t h e r m o s t a t i c a l l y controlled h e a t i n g b l a n k e t . The a n i m a l was fixed in a B i s h o p t y p e s t e r e o t a x i c app a r a t u s facing a 114 c m t a n g e n t screen w i t h a l u m i n a n c e of a p p r o x i m a t e l y 10 c d / m 2. The pupils were d i l a t e d b y a p p l y i n g t r o p i c a m i d a n d p h e n y l e p h e r i n e chloride (Midorin, S a n t e n Chemical). A pair of c o n t a n t lenses were selected f r o m a f a m i l y of lenses p r e p a r e d in 1/s d i o p t e r steps, so t h a t t h e r e t i n a was focussed on t h e screen using direct p r o j e c t i o n m e t h o d 17. F r o m t h e p o s i t i o n of t h e b l i n d s p o t s p r o j e c t e d b y t h e m e t h o d , t h e area centralis of e a c h eye was m a r k e d on t h e screen using t h e d a t a of V a k k u r et al. is. A slit of light of a d j u s t a b l e d i m e n s i o n s a n d o r i e n t a t i o n was p r o j e c t e d on t h e screen. I t could be m o v e d b a c k a n d f o r t h b y a pair of m i r r o r s a t t a c h e d to m o v i n g coil g a l v a n o m e t e r s . A m e c h a n i c a l s h u t t e r , o p e r a t e d electrically, was e m p l o y e d for flashing t h e slit of light. The i n t e n s i t y of t h e slit of l i g h t w a s a b o u t 60 c d / m ~. Single u n i t s were r e c o r d e d e x t r a c e l l u l a r l y b y a glasscoated tungsten microelectrode inserted through the d u r a m a t t e r . The t r e p h i n e hole in t h e c r a n i u m was sealed w i t h soft b o n e w a x to m i n i m i z e b r a i n m o v e m e n t . Once a u n i t was isolated, its o p t i m a l o r i e n t a t i o n was d e t e r m i n e d using slits of light m o v e d in a d i r e c t i o n p e r p e n d i c u l a r to t h e slit's o r i e n t a t i o n . T h e r e a f t e r , a flashing slit of light, o r i e n t e d parallel to t h e r e c e p t i v e field o r i e n t a t i o n , was used for t h e stimulus. A v e r a g e r e s p o n s e h i s t o g r a m s (bin w i d t h = 10 ms) were o b t a i n e d over 20 p r e s e n t a t i o n s of this stimulus. The s p o n t a n e o u s firing of a u n i t was also collected w i t h b a c k g r o u n d i l l u m i n a t i o n alone. The average r e s p o n s e of t h e u n i t was c o m p a r e d w i t h t h e spont a n e o u s firing, in order to classify t h e u n i t as ' s u s t a i n e d ' or ' t r a n s i e n t ' . R e c e p t i v e fields were also classified as simple or c o m p l e x cells according to t h e criteria set b y H u b e l a n d Wiese119, 20 W e c o n s i d e r e d t h e r e f o r e as simple cells only t h o s e o r i e n t a t i o n specific units w h o s e r e c e p t i v e fields could be s u b d i v i d e d into s p a t i a l l y d i s t i n c t on- a n d off-areas, a n d whose responses were m a x i m a l w i t h stimuli filling an entire on- or off-area. W e c o n s i d e r e d as c o m p l e x cells t h o s e o r i e n t a t i o n specific cells w h i c h e i t h e r did n o t s h o w a s e p a r a t i o n of t h e r e c e p t i v e field into e x c i t a t o r y areas, or w h i c h did n o t s h o w s u m m a t i o n of t h e s t i m u l u s effect over such s e p a r a t e areas. Results a n d discussion. All u n i t s were r e c o r d e d f r o m an area w i t h i n H o r s l e y Clarke c o o r d i n a t e s a n t e r i o r 3-5 a n d lateral 4 5 m m , in o r d e r to a v o i d t h e b o r d e r b e t w e e n area 17 a n d 18. A n d also t o a v o i d recording f r o m t h e u p p e r b a n k of t h e s u p r a - s p l e n i a l sulcus, electrodes were a d v a n c e d up to 2 m m f r o m t h e cortical surface. Most u n i t s of t h e s a m p l e h a d t h e i r r e c e p t i v e fields l o c a t e d 7-20 ~ lateral f r o m t h e v e r t i c a l m e r i d i a n a n d 8-25 ~ below t h e h o r i z o n t a l meridian. W e h a v e always c h e c k e d u p on t h e m a t t e r t h a t r e c e p t i v e fields of u n i t s r e c o r d e d f r o m an area w i t h i n lateral 3 a n d a n t e r i o r 3-5 m m were l o c a t e d n e a r e r t o t h e v e r t i c a l m e r i d i a n t h a n t h o s e of t h e s a m p l e d units. The cells of the s a m p l e were a c t u a l l y r e g i s t r a t e d in area 18. W e o b s e r v e d 3 c h a r a c t e r i s t i c t y p e s of responses to flashing slits of light w i t h i n r e c e p t i v e fields. T h e s e are s h o w n in average r e s p o n s e h i s t o g r a m s of t h e figure, w i t h arrows to i n d i c a t e t h e m e a n s p o n t a n e o u s firing r a t e of t h e unit. The first t y p e of t h e u n i t is i l l u s t r a t e d b y t h e h i s t o g r a m s in t h e figure A. I t gave a t r a n s i e n t r e s p o n s e to a flashing slit of light. A f t e r t h e t r a n s i e n t response, t h e firing r a t e
479
i m m e d i a t e l y fell to t h e s p o n t a n e o u s level. T h e r e c e p t i v e field was s u b d i v i d e d into s p a t i a l l y d i s t i n c t on- a n d offareas. The second t y p e of t h e u n i t is i l l u s t r a t e d b y t h e histo-, g r a m s in t h e figure B. I t h a d a r e c e p t i v e field profile similar to t h e first t y p e . I t gave a s u s t a i n e d r e s p o n s e t o a slit of light w i t h i n on-area. The r e s p o n s e r e m a i n e d m o r e t h a n t 0 spikes/sec a b o v e t h e s p o n t a n e o u s r a t e a f t e r 5 sec. W i t h i n off-area, t h i s u n i t gave a t r a n s i e n t r e s p o n s e to off-stimulus of t h e slit of light. T h e t h i r d t y p e of t h e u n i t is i l i u s t r a t e d b y t h e h i s t o g r a m s in t h e figure, C. I t gave a t r a n s i e n t r e s p o n s e to b o t h ona n d o f f - s t i m u l i of a slit of l i g h t w i t h i n its r e c e p t i v e field. T h e first a n d second t y p e s were classified as simple ceils, a n d t h e t h i r d as c o m p l e x cells. Of 137 u n i t s e n c o u n t e r e d , 42 were simple cells, 73 were c o m p l e x cells, a n d t h e rem a i n i n g 22 cells were n o t classified in t h e s i m p l e / c o m p l e x s c h e m e either. Of 42 simple cells, 34 gave p u r e t r a n s i e n t r e s p o n s e s to f l a s h i n g slits of light, a n d o n l y 8 gave s u s t a i n e d r e s p o n s e s t o s t a t i o n a r y slits of light w i t h i n onarea. All of t h e c o m p l e x cells e n c o u n t e r e d gave t r a n s i e n t responses. Therefore, of simple a n d c o m p l e x cells in area 18, 93% were of t r a n s i e n t t y p e . I n c o n t r a s t to area 18, in area 17, 61% o u t of simple a n d c o m p l e x cells were t r a n s i e n t t y p e a n d s u s t a i n e d r e s p o n s e s were o b s e r v e d b o t h in t h e simple a n d c o m p l e x cells 21. Therefore, ' t r a n s i e n t ' cells were m u c h m o r e f r e q u e n t in area 18 t h a n in area 17. A n o t h e r difference was t h a t s u s t a i n e d r e s p o n s e s were n o t o b s e r v e d in t h e c o m p l e x cells e n c o u n t e r e d in area 18. The g r e a t m a j o r i t y of area 18 cells g a v e p u r e t r a n s i e n t responses. This is c o n s i s t e n t w i t h tile f a c t t h a t Y-cells c o n s t i t u t e t h e only i n p u t f r o m t h e L G N t o area 18. H o w ever, our d a t a h a v e s h o w n t h a t a few simple cells in a r e a 18 give s u s t a i n e d responses, w h i c h X-cells are likely t o give.
7 8 9 10 ll 12 13 14 15 16 17 18 19 20 21
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