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The peripheral pathway for extracranial vasodilatition in the cat
Journal of the Autonomic Nervous System, 10 (1984) 145-155 Elsevier
145
JAN 00337
The peripheral pathway for extracranial vasodilatation in the cat P.J. Goadsby, G.A. L a m b e r t a n d J.W. L a n c e Department of Neurology, The Prince Henry Hospital and School of Medicine, University of New South Wales, Sydney (Australia) (Received October 18th, 1983) (Revised version received December 29th, 1983) (Accepted January 20th, 1984)
Key words: cat - facial nerve - vasodilation - pterygopalatine ganglion - otic ganglion
Abstract The locus coeruleus was electrically stimulated in 27 cats with high spinal cord sections. C o m m o n carotid blood flow was measured using electromagnetic flow probes, and arterial resistance calculated from mean arterial blood pressure and flow. Activation of the locus coeruleus caused an ipsilateral decrease in common carotid resistance, an effect previously demonstrated to depend on the integrity of the facial nerve. This vasodilator response is now shown to be mediated approximately equally by the pterygopalatine (sphenopalatine) and otic ganglia.
Introduction It is now nearly 140 years since Pieschel [13] described an anatomical connection between the greater superficial petrosal (GSP) nerve and the internal carotid artery. Nearly a century passed before the significance of this connection was to be systematically explored. In their classical work Chorobski and Penfield [3] stimulated the facial nerve, observing (with the pial window technique) dilatation of the pial vessels. This response was mediated via the GSP nerve which runs with the Correspondence: P.J. Goadsby, Department of Neurology, Clinical Sciences Building, The Prince Henry Hospital, Little Bay, N.S.W., Australia 2036. 0165-1838/84/$03.00 © 1984 Elsevier Science Publishers B.V.
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nervus intermedius in both monkey and cat, with a synaptic relay in small ganglia contained in the tract which joins the GSP and pericarotid plexus. Cobb and Finesinger [4] showed that pial vessel dilatation in response to vagal stimulation was also mediated via the facial nerve. Whether or not the second order neurone in the GSP vasodilator pathway extends to the cerebral parenchymal vasculature, and whether any such connections may mediate physiologically significant roles is not clear. Neurosurgical observations of facial flushing with irritative lesions of the Gasserian ganglion ([12]-- thermocoagulation; [14]-- alcohol injections) have led to the suggestion that the facial nerve may be involved in this response. Gonzales et al. [10] stimulated the Gasserian ganglion in the cat and observed increases in the facial temperature which they attributed to stimulation of GSP fibres distributed with the trigeminal nerve, although no direct anatomical connections between the trigeminal and GSP nerves was demonstrated. Unpublished observations from our laboratory have shown that volume of common carotid flow increases during trigeminal ganglion stimulation in the cat, and that this response is mediated mainly (80%) through a reflex pathway entering the brainstem in the trigeminal root and emerging with the facial nerve. Stimulation of the locus coeruleus in the monkey produces a differential resistance response in cerebral and extracerebral vascular beds, with constriction in the internal carotid circulation and dilatation in the external carotid circulation [7]. A similar extracranial vasodilator response obtained from the locus coeruleus in the cat is mediated by the facial nerve [8]. The GSP nerve thus appears to play an important role in extracranial vasodilatation in cat and man. The present experiments were undertaken to determine which ganglion or ganglia contain the synaptic relay of the vasodilator pathway.
Methods
27 adult male and female cats, average weight 3.17 _+ 0.94 kg (mean + S.D.), were anesthetized with a mixture of a-chlorolose (20 m g - k g -1) and urethane (500 m g . kg 1). Polyethylene catheters were inserted into a femoral artery for the purpose of monitoring systemic blood pressure, and into the femoral vein for the injection of drugs. The animals were intubated, paralyzed with gallamine, and artifical ventilation was adjusted to maintain a constant end-expiratory CO 2 level. Body temperature was kept constant by use of a heating blanket. The animals were first subjected to spinal cord section at the C 1 / C 2 level to eliminate any possible peripheral effects of locus coeruleus stimulation.
Flow monitoring The carotid arteries were exposed bilaterally and fitted with appropriately-sized electromagnetic flow probes. Blood pressure and common carotid flow were monitored bilaterally and values registered continuously during the experiment by a N A R C O Biosystems pen recorder. C o m m o n carotid vascular resistance was calcu-
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lated as the ratio blood pressure/flow by an analogue divider circuit and also displayed continuously on the recorder. Response to stimulation were likewise monitored on-line by a Z80-based microprocessor using a F O R T R A N programme. Viewing and plotting of data was subsequently performed with a programme written in the C programming language, and an X - Y plotter. The details of the calibration of the systems have been presented elsewhere [8].
Stimulus site and modes of stimulation The cats were mounted in stereotaxic frame, a skin flap turned, a burr hole placed in the calvarium and the dura reflected for the introduction of the electrode. The locus coeruleus was stimulated at AP - 2.0, H - 3.0 and L 2.5 [2] with the electrode angled at 40 o in the AP plane. A bipolar stainless steel electrode (Rhodes NEX-100), insulated except for 0.5 m m at the tip, was used to deliver paired opposite-polarity pulses (0.2-200 s -1, 500 gA, 250 gs, 500/~s separation) from two Grass constantcurrent units driven by two Grass stimulus-isolation units which were in turn driven by a Grass $88 stimulator. Each period of stimulation lasted for 15 s.
Surgical approaches to the ganglia The pterygopalatine ganglion was removed via a superior approach. The eye was mobilized and reflected antero-laterally, revealing the fascial covering of the ganglion lying in the floor of the orbit. This covering was removed carefully, and the ganglion and its accompanying vein and artery identified. If required, the medial aspect of the orbit was drilled away to uncover completely the anterior pole of the ganglion. The pterygopalatine ganglion was then removed and subsequently examined histologically to confirm its structural integrity. The otic ganglion of the cat lies deep to the trigeminal ganglion in a bone-covered fossa. It was approached from the postero-lateral aspect. Overlying skin and fascia were reflected, and bone drilled away with a high speed drill fitted with a dental burr. With some practice it was possible to approach directly the intact ganglion, control stimuli were then performed before the ganglion was removed. The ganglion was later examined histologically to confirm this (Fig. 1).
Histology Placement of the stimulating electrode in the locus coeruleus was verified as previously described using a Pearl's reaction [8]. Ganglion structure was examined, after staining with haematoxylin and eosin, to check that the ganglia had been removed.
Statistics Means and standard errors of the means were calculated for each of the frequencies of stimulation using a HP-41C programmable calculator. Raw data were analyzed under the following model: Y = u + X t + X f -4- X c --t--Xft + Xfc --[--Xct + Xft c -~- E R R O R where Y = observed response; u = mean response; X t = variation due to treatments;
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L
Fig. 1. Sketches of the anatomy of the pterygopalatine and otic ganglia in the cat. A: the eye has been lifted superiorly to reveal the contents of the floor of the orbit which includes the pterygopalatine ganglion. Abbreviations: A = pterygopalatine ganglion; B = infraorbital n.; C = minor palatine n.; D = maxillary branch of V; E = pterygopalatine n.: F = nerve of the pterygoid canal; G = medial pterygoid muscle; H = lateral pterygoid muscle; I = eye. B: the bony covering over the otic ganglion has been removed to demonstrate its relationship to the trigeminal ganglion. Abbreviations: A = otic ganglion: B = mandibular branch of V; C = auriculotemporal n.
X F = v a r i a t i o n d u e to f r e q u e n c y ; X c = v a r i a t i o n d u e to cat; Xfc = i n t e r a c t i o n frequency/cat; Xr, = i n t e r a c t i o n - f r e q u e n c y / t r e a t m e n t ; Xct = i n t e r a c t i o n c a t / t r e a t m e n t ; X ftc = i n t e r a c t i o n - f r e q u e n c y / t r e a t m e n t / c a t ; E R R O R = residual. A t h r e e - w a y analysis o f v a r i a n c e p r o c e d u r e [15] was c a r r i e d o u t o n the U n i v e r s i t y o f N . S . W . C Y B E R - 1 7 2 c o m p u t e r e m p l o y i n g statistics p r o g r a m s w r i t t e n in A P L (A P r o g r a m m i n g L a n g u a g e ) . F r e q u e n c y - r e s p o n s e c u r v e s w e r e t h e n fitted, u s i n g the m e a n s of t h e d a t a across cats, to a q u a d r a t i c p o l y n o m i a l regression. T h e s e c u r v e s c o u l d t h e n b e tested for d i f f e r e n c e s in their p a r a m e t e r s u s i n g a S t u d e n t ' s t-test. All tests w e r e c a r r i e d o u t at the P < 0.05 level of s i g n i f i c a n c e unless o t h e r w i s e i n d i c a t e d .
Results In 27 spinal cats, m e a n arterial b l o o d p r e s s u r e was 94.2 + 20.4 m m Hg, right c o m m o n c a r o t i d b l o o d f l o w 28.7 + 9.93 ml m i n - 1 a n d left c o m m o n c a r o t i d b o o d f l o w 27.7 + 13.36 ml m i n -1. R i g h t a n d left c o m m o n c a r o t i d v a s c u l a r resistances w e r e 3.97 + 1.22 a n d 4.48 + 1.89 m m H g . m l - 1. m i n l, r e s p e c t i v e l y ( m e a n + S.D.).
Control T h e m e a n m a x i m a l d e c r e a s e in v a s c u l a r r e s i s t a n c e in the spinal cat d u r i n g locus c o e r u l e u s s t i m u a t i o n was 24.0 + 2.0% on the ipsilateral side, w h i l e on the c o n t r a l a t e r a l side it was 11 + 2.0% (Fig. 2). T h i s r e s p o n s e was f r e q u e n c y - d e p e n d e n t o v e r t h e r a n g e 0 . 2 - 2 0 0 sec l (Fig. 3; Fig. 4).
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Fig. 2. Computer-processed plot for control responses to locus coeruleus stimulation from 15 spinalized cats. Mean response (solid line) and standard errors of the means (broken lines) are shown for percentage changes in blood pressure (BP), ipsilateral common carotid flow (lpsi-CCF), contralateral common carotid flow (Contra-CCF), ipsilateral common carotid resistance (Ipsi-CCR) and contralateral common carotid resistance (Contra-CCR) during and after stimulation of the locus coeruleus at 20 s-]. The common carotid resistance changes are mediated by the facial nerve, and the response seen here after high spinal cord section is the control response for the experimental group. The stimulus lasted for 15 s (solid line).
Pterygopalatine ganglion R e m o v a l of the pterygopalatine ganglion ipsilateral to the site of s t i m u l a t i o n resulted in a decrease in the dilator response to a little more than half that of control, a decrement which was significant for the whole cohort of a n i m a l s (F0.0t ( 1 , 4 5 ) = 28.1; Fig. 5). The m e a n m a x i m u m decrease i n resistance after ipsilateral g a n g l i o n removal was 16.5 + 3.7% ipsilaterally a n d 14.9 + 5.2% contralaterally, at a s t i m u l a t i o n frequency of 20 s - t . C o m p a r i s o n with the control curve for ipsilateral resistance showed that the coefficients of the regressions were n o t equal (T12 = 4.96, P < 0.001), while the contralateral resistance was u n c h a n g e d (T12 = 0.70). Con-
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Ipsilateral PTYG/OTIC ganglia removed T
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Fig. 3. Computer-processed data for the response of the facial nerve dilator pathway after removal of the ipsilateral pterygopalatine and otic ganglia, showing the contralateral response intact after ipsilateral ganglion removal. Abbreviations as for Fig. 2.
tralateral pterygopalatine ganglion removal resulted in a small but significant increase in the ipsilateral dilator response (Fo0~ (1,27)= 11.01), with the mean m a x i m u m decrease in resistance being 31.3_+ 10.1 at 20 s ~ although the f r e q u e n c y - r e s p o n s e curve itself was identical for all coefficients of the regressions (Tl2 = 0.35, 0.60, 0 . 4 6 ; Fig. 6). The contralateral resistance change was blocked after contralateral ganglion removal. The effect of ipsilateral ganglion removal on the dilator response was significantly different from the effect of contralateral ganglion removal (T12 = 2.87, P < 0.02). Bilateral removal of the pterygopalatine ganglion resulted in a decrease in the facial nerve dilator response (Fo.01 (1,81)= 21.5), with a mean m a x i m u m decrease in ipsilateral vascular resistance of 17.3 + 6.0% at 20 s ~. The f r e q u e n c y - r e s p o n s e curve was again significantly different from the control curve (T~2 = 2.79, P < 0.02).
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LOCUS COERULEUS STIMULATION:
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FREQUENCY (sec1) Fig. 4. Frequency-response curves showing the percentage decrease in ipsilateral c o m m o n carotid resistance mediated by the facial nerve during locus coeruleus stimulation. The 3 curves show the control response in an animal after high spinal cord section and the effect of pterygopalatine (Ipsi-Ptyg) or otic (lpsi-Otic) ganglion removal on this control response. Each point represents the mean of between 7 and 15 animals. The points were fitted to a quadratic polynomial regression as outlined. The difference between both the ganglion removal curves and the control curve was significant; however, the difference between the two ganglion removal curves was not.
Otic ganglion Removal of the otic ganglion ipsilateral to stimulation decreased the ipsilateral dilator response to a little more than half of control (F0.01 (1,45)= 15.7), the mean maximum decrease in ipsilateral resistance after ganglion removal being 18.1 + 3.9% at 100 s- 1. There was, however, no change in the resistance response contralateral to ganglion removal with the mean maximum response remaining at 10.5 ___3.0% (T12 = 0.14). Subsequent removal of the ipsilateral pterygopalatine ganglion blocked the ipsilateral response entirely but did not affect the contralateral response at all (T12 = 0.19). The effect of either ipsilateral pterygopalatine or otic ganglion removal on the facial dilator response was not significantly different (F0.05 (1,45)= 3.97).
Discussion
This paper represents the first attempt to investigate quantitatively the peripheral component of the facial (GSP) nerve vasodilator pathway. Although it may seem
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EXTRACRANIAL VASODILATATION -25
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Fig. 5. Effect of removal of the pterygopalatine and otic ganglia on the dilator response to locus coeruleus stimulation. The ordinate represenls the percentage decrease in common carotid vascular resistance (CCR) with activation of the locus coeruleus. The abscissa contains the control response (CTRL) both ipsilaterally (Ipsi-) and contralaterally (Contra-) and the effect on both these resistances of the removal of one or both of the pterygopalatine (PTYG) and otic (OTIC) ganglia. logical to assume the involvement of both p t e r y g o p a l a t i n e and otic ganglia, the extent of this involvement could not have been predicted. Certainly the large p a r t of the response m e d i a t e d b y the otic ganglion was surprising.
Controls T h e spinal cat was selected for these investigations for several reasons. Since we have d e v e l o p e d a reliable a n d stable model of facial nerve m e d i a t e d extracranial v a s o d i l a t a t i o n b y s t i m u l a t i n g the locus coeruleus, the u n w a n t e d p e r i p h e r a l effects of locus coeruleus activation h a d to be eliminated. The pressor response to locus coeruleus s t i m u l a t i o n would have confused the study of c r a n i o v a s c u l a r resistance changes, not to m e n t i o n its adverse effects on the surgical m a n o e u v r e s required to isolate the ganglia. S t i m u l a t i o n of the locus coeruleus in the m o n k e y m o d e l h a d also previously shown that, at a p p r o p r i a t e frequencies, the response was entirely extracerebral a n d therefore a n a l a g o u s to that seen with trigeminal ganglion stimulation. In a previous investigation it had also been shown that elicitation of the v a s o d i l a t o r response is well localized to the locus coeruleus [8]. In addition, chemical s t i m u l a t i o n of the locus coeruleus with L-glutamate r e p r o d u c e s the response seen
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EXTRACRANIAL VASODILATATION: CONTRALATERAL RESISTANCE -20
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Fig. 6. Effect of various maneuvers on activation on the facial nerve dilator pathway contralateral to the side of stimulation. The ordinate represents the percentage decrease in contralateral common carotid resistance (Contra-CCR). The abscissa represents the effect of removal of either the pyterygopalatine or otic ganglia both ipsilateral and contralateral to the side of stimulation. Abbreviations as for Fig. 5.
with electrical stimulation, a n d is equally well localized [9], d e m o n s t r a t i n g that the r e s p o n s e investigated here arises from activation of cell b o d i e s in the central nervous system, n o t fibers o f passage. Finally, we h a d shown that the response is entirely m e d i a t e d b y the facial nerve in that section of nerve c o m p l e t e l y abolishes the d i l a t o r r e s p o n s e to locus coeruleus s t i m u l a t i o n [8]. W e are thus a b l e to confine o u r c o n c l u s i o n s exclusively to the e x t r a c e r e b r a l facial d i l a t o r p a t h w a y , with no o t h e r p e r i p h e r a l nerve being involved.
lpsilateral dilatation R e m o v a l of the p t e r y g o p a l a t i n e ganglion ipsilateral to s t i m u l a t i o n led to a significant r e d u c t i o n in the facial d i l a t o r r e s p o n s e to a b o u t half that of control. C o n t r a l a t e r a l p t e r y g o p a l a t i n e ganglion r e m o v a l caused a small increase in the i p s i l a t e r a l d i l a t o r response, since the f r e q u e n c y - r e s p o n s e curves were indentical, the significance of these small increases is uncertain. It was c o n c l u d e d that the p t e r y g o p a l a t i n e ganglion was r e s p o n s i b l e for the p e r i p h e r a l d i s t r i b u t i o n of a p p r o x i m a t e l y h a l f the facial d i l a t o r p a t h w a y . Likewise, ipsilateral otic ganglion r e m o v a l halved the facial d i l a t o r response. T h e
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reduction caused by either ipsilateral pterygopalatine or otic ganglion removal was not different quantitatively, nor in its frequency responsiveness. This further suggests that the peripheral pathway is somewhat homogenous, and equally distributed to the pterygopalatine and otic ganglia. Section of both the ganglia in either order results in complete abolition of the ipsilateral dilator response. It therefore appears that the response is entirely mediated via these ganglia. Contralateral dilatation Removal of the pterygopalatine ganglion ipsilateral to stimulation did not alter the contralateral response, while removal of the ganglion contralateral to stimulation blocked the contralateral response completely. Similarly, ipsilateral otic ganglion removal had no effect on the contralateral response. Removal of both pterygopalatine and otic ganglia ipsilaterally, while completely blocking the ipsilateral resistance response, had no effect on the contralateral response. It is concluded that the contralateral response traverses the pterygopalatine ganglion probably exclusively. It must, however, be noted that the relatively small response (10% decrease in resistance) occurring contralaterally, if halved to 5% by pterygopalatine ganglion removal, would be difficult to quantitate reliably with our present experimental technique. The question of the contralateral response may require further examination in a species in which it is initially larger. Anatomical considerations Anatomically, the distribution of the GSP nerve to both the pterygopalatine [6,11] and otic ganglia [16] is wel~ established. The results therefore are consistent with known anatomical facts, although there seems little literature on the physiological role of the connections between the GSP and the otic ganglion. The outflow from the pterygopalatine ganglion is well known to cause vasodilatation in certain areas such as the nasal mucosa [1]. Clinical implications The division of the facial dilator pathway suggests some interesting prospects. Observations in this laboratory, as yet unpublished, have shown that stimulation of the trigeminal ganglion increases carotid blood flow and skin temperature mainly by a reflex pathway entering the brainstem by the trigeminal root and leaving by the facial nerve. Trigeminal ganglion stimulation in the cat increases local "anial blood flow selectively, for example, mandibular branch stimulation has b .,1 shown to increase temperature in the skin overlying the lower jaw [10]. Thermocoagulation of the Gasserian (trigeminal) ganglion, employed for the relief of trigeminal neuralgia in man, causes flushing of the face in the approximate skin area supplied by the trigeminal division stimulated [5]. It is possible that trigeminal pathways may have a topographical reflex projection via the GSP nerve to either the pterygopalatine or otic ganglion to produce the localized response that has been observed in cat and man.
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Acknowledgements The authors wish to thank Mr. J.W. Duckworth for help in the execution of these experiments. We would also like to thank Ms. Kathy Mulligan, Dept. Anatomy U.N.S.W., and Professor B. Warren, Dept. Pathology P.H.H., for the sectioning and staining of some of the ganglia removed during the experiments, and Professor C.R.R. Watson, Dept. Anatomy U.N.S.W., for advice on the anatomy of the pterygopalatine ganglion. Statistical advice was kindly rendered to us (P.J.G.) by Dr. J.C. Eccleston, U.N.S.W. Dept. Statistics. The authors also thank the Department of Medical Illustration for photographing all figures. This programme has been supported by the National Health and Medical Research Council of Australia and by grants from the J.A. Perini Family Trust, the Basset Trust and the Australian Brain Foundation.
References 1 Anggard, A., The effects of parasympathetic nerve stimulation on the microcirculation and secretion in the nasal mucosa of the cat, Acta Otolaryngol., 78 (1974) 98-105. 2 Berman, A.L., The Brain Stem of the Cat. A Cytoarchitectonic Atlas with Stereotaxic Coordinates, University of Wisconsin Press, London, 1968. 3 Chorobski, J. and Penfield, W., Cerebral vasodilator nerves and their pathway from the medulla oblongata, Arch. Neurol. Psychiat., 28 (1932) 1257-1289. 4 Cobb, S. and Finesinger, J.E., Cerebral circulation XIX. The vagal pathway of the vasodilator impulses, Arch. Neurol. Psychiat., 28 (1932) 1243-1256. 5 Drummond, P.D., Gonski, A. and Lance, J.W., Facial flushing after thermocoagulation of the gasserian ganglion, J. Neurol. Neurosurg. Psychiat., (1983) in press. 6 Gardner, E., Gray, D.J. and O'Rahilly, R., Anatomy, W.B. Saunders, London, 1975. 7 Goadsby, P.J., Lambert, G.A. and Lance, J.W., Differential effect on internal and external carotid blood flow in the monkey evoked by locus coeruleus stimulation, Brain Res., 249 (1982) 247-254. 8 Goadsby, P.J., Lambert, G.A. and Lance, J.W., Effects of locus coeruleus stimulation on carotid vascular resistance in the cat, Brain Res., 278 (1983) 173-185. 9 Goadsby, P.J., Lambert, G.A. and Lance, J.W., Dilatation in the carotid vascular territory of the cat in response to activation of cell bodies in the locus coeruleus, Clin. exp. Neurol., (1983) in press. 10 Gonzales, G., Onofrio, B.M. and Kerr, F.W.L., Vasodilator system for the face, J. Neurosurg., 42 (1975) 696-703. 11 Mitchell, G.A.G. and Learmonth, J., Anatomy of the Autonomic Nervous System, E. and S. Livingstone London, 1953, pp. 160-175. 12 Onofrio, B.M., Radio frequency percutaneous Gasserian ganglion lesions, Neurosurgery, 42 (1975) 132-143. 13 Pieschel, e., De parte cephalica nervi sympathici in equo prodrumus, Leipzig, E. Stange, 1844; quoted by Chorobski and Penfield, 1932. 14 Sweet, W.M. and Wepsic J.G., Controlled thermocoagulation of V ganglion and rootlets for differential destruction of pain fibres. Part I. V. Neuralgia, J. Neurosurg., 40 (1974) 143-156. 15 Wetherill, G.B., Intermediate Statistical Methods, Chapman and Hall, New York, 1981. 16 Williams, P.L. and Warwick, R., Grays Anatomy, 36th, Edn., Churchill-Livingston, Melbourne, 1980.
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JAN 00337
The peripheral pathway for extracranial vasodilatation in the cat P.J. Goadsby, G.A. L a m b e r t a n d J.W. L a n c e Department of Neurology, The Prince Henry Hospital and School of Medicine, University of New South Wales, Sydney (Australia) (Received October 18th, 1983) (Revised version received December 29th, 1983) (Accepted January 20th, 1984)
Key words: cat - facial nerve - vasodilation - pterygopalatine ganglion - otic ganglion
Abstract The locus coeruleus was electrically stimulated in 27 cats with high spinal cord sections. C o m m o n carotid blood flow was measured using electromagnetic flow probes, and arterial resistance calculated from mean arterial blood pressure and flow. Activation of the locus coeruleus caused an ipsilateral decrease in common carotid resistance, an effect previously demonstrated to depend on the integrity of the facial nerve. This vasodilator response is now shown to be mediated approximately equally by the pterygopalatine (sphenopalatine) and otic ganglia.
Introduction It is now nearly 140 years since Pieschel [13] described an anatomical connection between the greater superficial petrosal (GSP) nerve and the internal carotid artery. Nearly a century passed before the significance of this connection was to be systematically explored. In their classical work Chorobski and Penfield [3] stimulated the facial nerve, observing (with the pial window technique) dilatation of the pial vessels. This response was mediated via the GSP nerve which runs with the Correspondence: P.J. Goadsby, Department of Neurology, Clinical Sciences Building, The Prince Henry Hospital, Little Bay, N.S.W., Australia 2036. 0165-1838/84/$03.00 © 1984 Elsevier Science Publishers B.V.
146
nervus intermedius in both monkey and cat, with a synaptic relay in small ganglia contained in the tract which joins the GSP and pericarotid plexus. Cobb and Finesinger [4] showed that pial vessel dilatation in response to vagal stimulation was also mediated via the facial nerve. Whether or not the second order neurone in the GSP vasodilator pathway extends to the cerebral parenchymal vasculature, and whether any such connections may mediate physiologically significant roles is not clear. Neurosurgical observations of facial flushing with irritative lesions of the Gasserian ganglion ([12]-- thermocoagulation; [14]-- alcohol injections) have led to the suggestion that the facial nerve may be involved in this response. Gonzales et al. [10] stimulated the Gasserian ganglion in the cat and observed increases in the facial temperature which they attributed to stimulation of GSP fibres distributed with the trigeminal nerve, although no direct anatomical connections between the trigeminal and GSP nerves was demonstrated. Unpublished observations from our laboratory have shown that volume of common carotid flow increases during trigeminal ganglion stimulation in the cat, and that this response is mediated mainly (80%) through a reflex pathway entering the brainstem in the trigeminal root and emerging with the facial nerve. Stimulation of the locus coeruleus in the monkey produces a differential resistance response in cerebral and extracerebral vascular beds, with constriction in the internal carotid circulation and dilatation in the external carotid circulation [7]. A similar extracranial vasodilator response obtained from the locus coeruleus in the cat is mediated by the facial nerve [8]. The GSP nerve thus appears to play an important role in extracranial vasodilatation in cat and man. The present experiments were undertaken to determine which ganglion or ganglia contain the synaptic relay of the vasodilator pathway.
Methods
27 adult male and female cats, average weight 3.17 _+ 0.94 kg (mean + S.D.), were anesthetized with a mixture of a-chlorolose (20 m g - k g -1) and urethane (500 m g . kg 1). Polyethylene catheters were inserted into a femoral artery for the purpose of monitoring systemic blood pressure, and into the femoral vein for the injection of drugs. The animals were intubated, paralyzed with gallamine, and artifical ventilation was adjusted to maintain a constant end-expiratory CO 2 level. Body temperature was kept constant by use of a heating blanket. The animals were first subjected to spinal cord section at the C 1 / C 2 level to eliminate any possible peripheral effects of locus coeruleus stimulation.
Flow monitoring The carotid arteries were exposed bilaterally and fitted with appropriately-sized electromagnetic flow probes. Blood pressure and common carotid flow were monitored bilaterally and values registered continuously during the experiment by a N A R C O Biosystems pen recorder. C o m m o n carotid vascular resistance was calcu-
147
lated as the ratio blood pressure/flow by an analogue divider circuit and also displayed continuously on the recorder. Response to stimulation were likewise monitored on-line by a Z80-based microprocessor using a F O R T R A N programme. Viewing and plotting of data was subsequently performed with a programme written in the C programming language, and an X - Y plotter. The details of the calibration of the systems have been presented elsewhere [8].
Stimulus site and modes of stimulation The cats were mounted in stereotaxic frame, a skin flap turned, a burr hole placed in the calvarium and the dura reflected for the introduction of the electrode. The locus coeruleus was stimulated at AP - 2.0, H - 3.0 and L 2.5 [2] with the electrode angled at 40 o in the AP plane. A bipolar stainless steel electrode (Rhodes NEX-100), insulated except for 0.5 m m at the tip, was used to deliver paired opposite-polarity pulses (0.2-200 s -1, 500 gA, 250 gs, 500/~s separation) from two Grass constantcurrent units driven by two Grass stimulus-isolation units which were in turn driven by a Grass $88 stimulator. Each period of stimulation lasted for 15 s.
Surgical approaches to the ganglia The pterygopalatine ganglion was removed via a superior approach. The eye was mobilized and reflected antero-laterally, revealing the fascial covering of the ganglion lying in the floor of the orbit. This covering was removed carefully, and the ganglion and its accompanying vein and artery identified. If required, the medial aspect of the orbit was drilled away to uncover completely the anterior pole of the ganglion. The pterygopalatine ganglion was then removed and subsequently examined histologically to confirm its structural integrity. The otic ganglion of the cat lies deep to the trigeminal ganglion in a bone-covered fossa. It was approached from the postero-lateral aspect. Overlying skin and fascia were reflected, and bone drilled away with a high speed drill fitted with a dental burr. With some practice it was possible to approach directly the intact ganglion, control stimuli were then performed before the ganglion was removed. The ganglion was later examined histologically to confirm this (Fig. 1).
Histology Placement of the stimulating electrode in the locus coeruleus was verified as previously described using a Pearl's reaction [8]. Ganglion structure was examined, after staining with haematoxylin and eosin, to check that the ganglia had been removed.
Statistics Means and standard errors of the means were calculated for each of the frequencies of stimulation using a HP-41C programmable calculator. Raw data were analyzed under the following model: Y = u + X t + X f -4- X c --t--Xft + Xfc --[--Xct + Xft c -~- E R R O R where Y = observed response; u = mean response; X t = variation due to treatments;
148
L
Fig. 1. Sketches of the anatomy of the pterygopalatine and otic ganglia in the cat. A: the eye has been lifted superiorly to reveal the contents of the floor of the orbit which includes the pterygopalatine ganglion. Abbreviations: A = pterygopalatine ganglion; B = infraorbital n.; C = minor palatine n.; D = maxillary branch of V; E = pterygopalatine n.: F = nerve of the pterygoid canal; G = medial pterygoid muscle; H = lateral pterygoid muscle; I = eye. B: the bony covering over the otic ganglion has been removed to demonstrate its relationship to the trigeminal ganglion. Abbreviations: A = otic ganglion: B = mandibular branch of V; C = auriculotemporal n.
X F = v a r i a t i o n d u e to f r e q u e n c y ; X c = v a r i a t i o n d u e to cat; Xfc = i n t e r a c t i o n frequency/cat; Xr, = i n t e r a c t i o n - f r e q u e n c y / t r e a t m e n t ; Xct = i n t e r a c t i o n c a t / t r e a t m e n t ; X ftc = i n t e r a c t i o n - f r e q u e n c y / t r e a t m e n t / c a t ; E R R O R = residual. A t h r e e - w a y analysis o f v a r i a n c e p r o c e d u r e [15] was c a r r i e d o u t o n the U n i v e r s i t y o f N . S . W . C Y B E R - 1 7 2 c o m p u t e r e m p l o y i n g statistics p r o g r a m s w r i t t e n in A P L (A P r o g r a m m i n g L a n g u a g e ) . F r e q u e n c y - r e s p o n s e c u r v e s w e r e t h e n fitted, u s i n g the m e a n s of t h e d a t a across cats, to a q u a d r a t i c p o l y n o m i a l regression. T h e s e c u r v e s c o u l d t h e n b e tested for d i f f e r e n c e s in their p a r a m e t e r s u s i n g a S t u d e n t ' s t-test. All tests w e r e c a r r i e d o u t at the P < 0.05 level of s i g n i f i c a n c e unless o t h e r w i s e i n d i c a t e d .
Results In 27 spinal cats, m e a n arterial b l o o d p r e s s u r e was 94.2 + 20.4 m m Hg, right c o m m o n c a r o t i d b l o o d f l o w 28.7 + 9.93 ml m i n - 1 a n d left c o m m o n c a r o t i d b o o d f l o w 27.7 + 13.36 ml m i n -1. R i g h t a n d left c o m m o n c a r o t i d v a s c u l a r resistances w e r e 3.97 + 1.22 a n d 4.48 + 1.89 m m H g . m l - 1. m i n l, r e s p e c t i v e l y ( m e a n + S.D.).
Control T h e m e a n m a x i m a l d e c r e a s e in v a s c u l a r r e s i s t a n c e in the spinal cat d u r i n g locus c o e r u l e u s s t i m u a t i o n was 24.0 + 2.0% on the ipsilateral side, w h i l e on the c o n t r a l a t e r a l side it was 11 + 2.0% (Fig. 2). T h i s r e s p o n s e was f r e q u e n c y - d e p e n d e n t o v e r t h e r a n g e 0 . 2 - 2 0 0 sec l (Fig. 3; Fig. 4).
149
T
SPINAL CORD SECTION (control)
i %L~BP
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Fig. 2. Computer-processed plot for control responses to locus coeruleus stimulation from 15 spinalized cats. Mean response (solid line) and standard errors of the means (broken lines) are shown for percentage changes in blood pressure (BP), ipsilateral common carotid flow (lpsi-CCF), contralateral common carotid flow (Contra-CCF), ipsilateral common carotid resistance (Ipsi-CCR) and contralateral common carotid resistance (Contra-CCR) during and after stimulation of the locus coeruleus at 20 s-]. The common carotid resistance changes are mediated by the facial nerve, and the response seen here after high spinal cord section is the control response for the experimental group. The stimulus lasted for 15 s (solid line).
Pterygopalatine ganglion R e m o v a l of the pterygopalatine ganglion ipsilateral to the site of s t i m u l a t i o n resulted in a decrease in the dilator response to a little more than half that of control, a decrement which was significant for the whole cohort of a n i m a l s (F0.0t ( 1 , 4 5 ) = 28.1; Fig. 5). The m e a n m a x i m u m decrease i n resistance after ipsilateral g a n g l i o n removal was 16.5 + 3.7% ipsilaterally a n d 14.9 + 5.2% contralaterally, at a s t i m u l a t i o n frequency of 20 s - t . C o m p a r i s o n with the control curve for ipsilateral resistance showed that the coefficients of the regressions were n o t equal (T12 = 4.96, P < 0.001), while the contralateral resistance was u n c h a n g e d (T12 = 0.70). Con-
150
Ipsilateral PTYG/OTIC ganglia removed T
20 i
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,
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Fig. 3. Computer-processed data for the response of the facial nerve dilator pathway after removal of the ipsilateral pterygopalatine and otic ganglia, showing the contralateral response intact after ipsilateral ganglion removal. Abbreviations as for Fig. 2.
tralateral pterygopalatine ganglion removal resulted in a small but significant increase in the ipsilateral dilator response (Fo0~ (1,27)= 11.01), with the mean m a x i m u m decrease in resistance being 31.3_+ 10.1 at 20 s ~ although the f r e q u e n c y - r e s p o n s e curve itself was identical for all coefficients of the regressions (Tl2 = 0.35, 0.60, 0 . 4 6 ; Fig. 6). The contralateral resistance change was blocked after contralateral ganglion removal. The effect of ipsilateral ganglion removal on the dilator response was significantly different from the effect of contralateral ganglion removal (T12 = 2.87, P < 0.02). Bilateral removal of the pterygopalatine ganglion resulted in a decrease in the facial nerve dilator response (Fo.01 (1,81)= 21.5), with a mean m a x i m u m decrease in ipsilateral vascular resistance of 17.3 + 6.0% at 20 s ~. The f r e q u e n c y - r e s p o n s e curve was again significantly different from the control curve (T~2 = 2.79, P < 0.02).
151
LOCUS COERULEUS STIMULATION:
-40
-
Extracranial Vasodilatation • control • Ipsi-Ptyg • Ipsi-Otic
-30
°,,ZMpsi-CCR -20
-10
I
I
I
I
0
50
100
200
FREQUENCY (sec1) Fig. 4. Frequency-response curves showing the percentage decrease in ipsilateral c o m m o n carotid resistance mediated by the facial nerve during locus coeruleus stimulation. The 3 curves show the control response in an animal after high spinal cord section and the effect of pterygopalatine (Ipsi-Ptyg) or otic (lpsi-Otic) ganglion removal on this control response. Each point represents the mean of between 7 and 15 animals. The points were fitted to a quadratic polynomial regression as outlined. The difference between both the ganglion removal curves and the control curve was significant; however, the difference between the two ganglion removal curves was not.
Otic ganglion Removal of the otic ganglion ipsilateral to stimulation decreased the ipsilateral dilator response to a little more than half of control (F0.01 (1,45)= 15.7), the mean maximum decrease in ipsilateral resistance after ganglion removal being 18.1 + 3.9% at 100 s- 1. There was, however, no change in the resistance response contralateral to ganglion removal with the mean maximum response remaining at 10.5 ___3.0% (T12 = 0.14). Subsequent removal of the ipsilateral pterygopalatine ganglion blocked the ipsilateral response entirely but did not affect the contralateral response at all (T12 = 0.19). The effect of either ipsilateral pterygopalatine or otic ganglion removal on the facial dilator response was not significantly different (F0.05 (1,45)= 3.97).
Discussion
This paper represents the first attempt to investigate quantitatively the peripheral component of the facial (GSP) nerve vasodilator pathway. Although it may seem
152
EXTRACRANIAL VASODILATATION -25
-15
%~CCR
-5
0 0
CTRL
0
0
0
Ipsi-PTYG Ipsi.OTIC Ipsi-PTYG/OTIC
Fig. 5. Effect of removal of the pterygopalatine and otic ganglia on the dilator response to locus coeruleus stimulation. The ordinate represenls the percentage decrease in common carotid vascular resistance (CCR) with activation of the locus coeruleus. The abscissa contains the control response (CTRL) both ipsilaterally (Ipsi-) and contralaterally (Contra-) and the effect on both these resistances of the removal of one or both of the pterygopalatine (PTYG) and otic (OTIC) ganglia. logical to assume the involvement of both p t e r y g o p a l a t i n e and otic ganglia, the extent of this involvement could not have been predicted. Certainly the large p a r t of the response m e d i a t e d b y the otic ganglion was surprising.
Controls T h e spinal cat was selected for these investigations for several reasons. Since we have d e v e l o p e d a reliable a n d stable model of facial nerve m e d i a t e d extracranial v a s o d i l a t a t i o n b y s t i m u l a t i n g the locus coeruleus, the u n w a n t e d p e r i p h e r a l effects of locus coeruleus activation h a d to be eliminated. The pressor response to locus coeruleus s t i m u l a t i o n would have confused the study of c r a n i o v a s c u l a r resistance changes, not to m e n t i o n its adverse effects on the surgical m a n o e u v r e s required to isolate the ganglia. S t i m u l a t i o n of the locus coeruleus in the m o n k e y m o d e l h a d also previously shown that, at a p p r o p r i a t e frequencies, the response was entirely extracerebral a n d therefore a n a l a g o u s to that seen with trigeminal ganglion stimulation. In a previous investigation it had also been shown that elicitation of the v a s o d i l a t o r response is well localized to the locus coeruleus [8]. In addition, chemical s t i m u l a t i o n of the locus coeruleus with L-glutamate r e p r o d u c e s the response seen
153
EXTRACRANIAL VASODILATATION: CONTRALATERAL RESISTANCE -20
T
n.. ¢.J i
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-10
O
tw
i-to
>. I--. gg
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>-
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es m
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Fig. 6. Effect of various maneuvers on activation on the facial nerve dilator pathway contralateral to the side of stimulation. The ordinate represents the percentage decrease in contralateral common carotid resistance (Contra-CCR). The abscissa represents the effect of removal of either the pyterygopalatine or otic ganglia both ipsilateral and contralateral to the side of stimulation. Abbreviations as for Fig. 5.
with electrical stimulation, a n d is equally well localized [9], d e m o n s t r a t i n g that the r e s p o n s e investigated here arises from activation of cell b o d i e s in the central nervous system, n o t fibers o f passage. Finally, we h a d shown that the response is entirely m e d i a t e d b y the facial nerve in that section of nerve c o m p l e t e l y abolishes the d i l a t o r r e s p o n s e to locus coeruleus s t i m u l a t i o n [8]. W e are thus a b l e to confine o u r c o n c l u s i o n s exclusively to the e x t r a c e r e b r a l facial d i l a t o r p a t h w a y , with no o t h e r p e r i p h e r a l nerve being involved.
lpsilateral dilatation R e m o v a l of the p t e r y g o p a l a t i n e ganglion ipsilateral to s t i m u l a t i o n led to a significant r e d u c t i o n in the facial d i l a t o r r e s p o n s e to a b o u t half that of control. C o n t r a l a t e r a l p t e r y g o p a l a t i n e ganglion r e m o v a l caused a small increase in the i p s i l a t e r a l d i l a t o r response, since the f r e q u e n c y - r e s p o n s e curves were indentical, the significance of these small increases is uncertain. It was c o n c l u d e d that the p t e r y g o p a l a t i n e ganglion was r e s p o n s i b l e for the p e r i p h e r a l d i s t r i b u t i o n of a p p r o x i m a t e l y h a l f the facial d i l a t o r p a t h w a y . Likewise, ipsilateral otic ganglion r e m o v a l halved the facial d i l a t o r response. T h e
154
reduction caused by either ipsilateral pterygopalatine or otic ganglion removal was not different quantitatively, nor in its frequency responsiveness. This further suggests that the peripheral pathway is somewhat homogenous, and equally distributed to the pterygopalatine and otic ganglia. Section of both the ganglia in either order results in complete abolition of the ipsilateral dilator response. It therefore appears that the response is entirely mediated via these ganglia. Contralateral dilatation Removal of the pterygopalatine ganglion ipsilateral to stimulation did not alter the contralateral response, while removal of the ganglion contralateral to stimulation blocked the contralateral response completely. Similarly, ipsilateral otic ganglion removal had no effect on the contralateral response. Removal of both pterygopalatine and otic ganglia ipsilaterally, while completely blocking the ipsilateral resistance response, had no effect on the contralateral response. It is concluded that the contralateral response traverses the pterygopalatine ganglion probably exclusively. It must, however, be noted that the relatively small response (10% decrease in resistance) occurring contralaterally, if halved to 5% by pterygopalatine ganglion removal, would be difficult to quantitate reliably with our present experimental technique. The question of the contralateral response may require further examination in a species in which it is initially larger. Anatomical considerations Anatomically, the distribution of the GSP nerve to both the pterygopalatine [6,11] and otic ganglia [16] is wel~ established. The results therefore are consistent with known anatomical facts, although there seems little literature on the physiological role of the connections between the GSP and the otic ganglion. The outflow from the pterygopalatine ganglion is well known to cause vasodilatation in certain areas such as the nasal mucosa [1]. Clinical implications The division of the facial dilator pathway suggests some interesting prospects. Observations in this laboratory, as yet unpublished, have shown that stimulation of the trigeminal ganglion increases carotid blood flow and skin temperature mainly by a reflex pathway entering the brainstem by the trigeminal root and leaving by the facial nerve. Trigeminal ganglion stimulation in the cat increases local "anial blood flow selectively, for example, mandibular branch stimulation has b .,1 shown to increase temperature in the skin overlying the lower jaw [10]. Thermocoagulation of the Gasserian (trigeminal) ganglion, employed for the relief of trigeminal neuralgia in man, causes flushing of the face in the approximate skin area supplied by the trigeminal division stimulated [5]. It is possible that trigeminal pathways may have a topographical reflex projection via the GSP nerve to either the pterygopalatine or otic ganglion to produce the localized response that has been observed in cat and man.
155
Acknowledgements The authors wish to thank Mr. J.W. Duckworth for help in the execution of these experiments. We would also like to thank Ms. Kathy Mulligan, Dept. Anatomy U.N.S.W., and Professor B. Warren, Dept. Pathology P.H.H., for the sectioning and staining of some of the ganglia removed during the experiments, and Professor C.R.R. Watson, Dept. Anatomy U.N.S.W., for advice on the anatomy of the pterygopalatine ganglion. Statistical advice was kindly rendered to us (P.J.G.) by Dr. J.C. Eccleston, U.N.S.W. Dept. Statistics. The authors also thank the Department of Medical Illustration for photographing all figures. This programme has been supported by the National Health and Medical Research Council of Australia and by grants from the J.A. Perini Family Trust, the Basset Trust and the Australian Brain Foundation.
References 1 Anggard, A., The effects of parasympathetic nerve stimulation on the microcirculation and secretion in the nasal mucosa of the cat, Acta Otolaryngol., 78 (1974) 98-105. 2 Berman, A.L., The Brain Stem of the Cat. A Cytoarchitectonic Atlas with Stereotaxic Coordinates, University of Wisconsin Press, London, 1968. 3 Chorobski, J. and Penfield, W., Cerebral vasodilator nerves and their pathway from the medulla oblongata, Arch. Neurol. Psychiat., 28 (1932) 1257-1289. 4 Cobb, S. and Finesinger, J.E., Cerebral circulation XIX. The vagal pathway of the vasodilator impulses, Arch. Neurol. Psychiat., 28 (1932) 1243-1256. 5 Drummond, P.D., Gonski, A. and Lance, J.W., Facial flushing after thermocoagulation of the gasserian ganglion, J. Neurol. Neurosurg. Psychiat., (1983) in press. 6 Gardner, E., Gray, D.J. and O'Rahilly, R., Anatomy, W.B. Saunders, London, 1975. 7 Goadsby, P.J., Lambert, G.A. and Lance, J.W., Differential effect on internal and external carotid blood flow in the monkey evoked by locus coeruleus stimulation, Brain Res., 249 (1982) 247-254. 8 Goadsby, P.J., Lambert, G.A. and Lance, J.W., Effects of locus coeruleus stimulation on carotid vascular resistance in the cat, Brain Res., 278 (1983) 173-185. 9 Goadsby, P.J., Lambert, G.A. and Lance, J.W., Dilatation in the carotid vascular territory of the cat in response to activation of cell bodies in the locus coeruleus, Clin. exp. Neurol., (1983) in press. 10 Gonzales, G., Onofrio, B.M. and Kerr, F.W.L., Vasodilator system for the face, J. Neurosurg., 42 (1975) 696-703. 11 Mitchell, G.A.G. and Learmonth, J., Anatomy of the Autonomic Nervous System, E. and S. Livingstone London, 1953, pp. 160-175. 12 Onofrio, B.M., Radio frequency percutaneous Gasserian ganglion lesions, Neurosurgery, 42 (1975) 132-143. 13 Pieschel, e., De parte cephalica nervi sympathici in equo prodrumus, Leipzig, E. Stange, 1844; quoted by Chorobski and Penfield, 1932. 14 Sweet, W.M. and Wepsic J.G., Controlled thermocoagulation of V ganglion and rootlets for differential destruction of pain fibres. Part I. V. Neuralgia, J. Neurosurg., 40 (1974) 143-156. 15 Wetherill, G.B., Intermediate Statistical Methods, Chapman and Hall, New York, 1981. 16 Williams, P.L. and Warwick, R., Grays Anatomy, 36th, Edn., Churchill-Livingston, Melbourne, 1980.