Cardiovascular interactions of nonivamide, glyceryl nonivamide, capsaicin analogues, and substance P antagonist in rats

Brain Research Bulkfin, Vol. 30, pp. 641-648,

1993 Copyright

Printed in the USA. All rights reserved.

0361-9230/93 $6.00 + .OO 0 1993 Pergamon Press Ltd.

Cardiovascular Interactions of Nonivamide, Glyceryl Nonivamide, Capsaicin Analogues, and Substance P Antagonist in Rats JWU-LA1

YEH,

YI-CHING

LO, YUN

WANG*

AND

ING-JUN

CHEN’

Department of Pharmacology, Medicine Institute of Postgraduate, Kaohsiung Medical College, Kaohsiung, Taiwan, 80708 R.O.C. *Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan, R.O.C. Received

20 November

199 1; Accepted

3 June

1992

YEH, J. L., Y. C. LO, Y. WANG AND 1. J. CHEN. Cardiovascular interactions of nonivamide, glyceryl nonivamide, capsaicin analogues, and substance P antagonist in rats. BRAIN RES BULL 30(5/6) 641-648, 1993.-Nonanoyl vanillylamide-4-o-glycerol (glyceryl nonivamide, GLNVA) a nonpungent ether-linked derivative of nonanoyl vanillylamide (nonivamide, NVA) was compared to capsaicin (CAP) and NVA with regard to its depressor response in rats. IV injection of CAP and NVA (IO-’ to lo-’ mg/kg) in Wistar rats elicit a triphasic blood pressure response, bradycardia, and aponea. However, IV injection of GLNVA results in a monophasic reduction in blood pressure, with little effect on heart rate and respiration. The depressor response to GLNVA was not diminished by bilateral vagotomy or by systemic pretreatment with atropine. Following the CAP pretreatment, the delayed hypotension induced by CAP, NVA, and the hypotension of GLNVA was almost abolished. Injection of CAP, NVA (10 &kg), or GLNVA (100 fig/kg) into one femoral artery elicited a fall in blood pressure in the rat. This effect was abolished following intrathecal injection of substance P antagonist [D-Pro2, D-Trp7,9]- SP. Microejections of CAP, NVA, or GLNVA into the nucleus tractus solitarii (NTS) evoked hypotension, the bradycardia following microejection of CAP and NVA into the NTS occurred only at higher doses of GLNVA. From these results it is suggested that GLNVA appears to act more exclusively than CAP by stimulating peripheral perivascular small diameter C-fiber sensory nerves. Substance P antagonist Cardiovascular actions Capsaicin Intrathecal injection Arterial pressure

Nucleus tractus solitari

Vagus reflex

CAP have not been found to exceed potency of CAP. Today NVA is synthesized commercially on a large scale and provided as an ingredient in skin irritant preparations used to alleviate symptoms arising from rheumatic disorders. NVA has a pharmacological profile similar to that of CAP (1,9,22,23) and has been used as a substitute for CAP in neuropharmacological studies (7,20). NVA produces a triphasic blood pressure response similar to that of CAP, as well as bradycardia and aponea (20,3 I). In an attempt to attenuate the -strong pungent and irritating activities of CAP and NVA, as well as to eliminate the vasoconstriction and other untoward effects accompanying their use, glyceryl nonivamide (GLNVA, Fig. 1) was synthesized by this laboratory. GLNVA is a relatively nonpungent analogue of CAP in which the phenolic hydroxyl group is masked. The antinociceptive properties of GLNVA were described in an earlier report from this laboratory (4). In this study, the effects of GLNVA on the cardiovascular system are more comprehensively examined.

CAPSAICIN (CAP, 8-methyl-N-vanillyl-6-nonenamide; Fig. 1) is a pungent constituent of red pepper with a wide spectrum of

biological activities (2,17,28). The cardiovascular effects following central and peripheral administration of CAP have been extensively studied (26,27,30). IV injection of CAP in SpragueDawley rats elicits a triphasic blood pressure response, typified by an initial sharp reduction (effect A), which is followed by an increase to slightly higher than normal levels (effect B), and is concluded by a gradual fall in blood pressure (effect C) (5). The clinical applications of CAP as an antinociceptive agent are sharply limited by the vagus reflex that induces effect A, as well as the untoward bradycardia and aponea accompanying its use. Several analogues of CAP have been synthesized, and their biochemical and pharmacological activities have been evaluated with respect to those of CAP (1,l I ,22,23). Of all the synthetic derivatives, nonivamide (NVA, nonanoyl vanillylamide; see Fig. 1) had a high activity in several test systems. Nevertheless, even though resiniferatoxin has been found to be the most potent, natural pungent principle (21) NVA and other analogues of ’ To whom requests for reprints should be sent.

641

642

YEH

ii

HO

.CH,

CH,NHC- (CH2)4-CH’CH-CH.CH

3

Capsaicin ; 8-methyl-N-~niIlyl-nonenam~de (CAP)

ET

AL.

Capsaicin pretreatment was carried out 7 days prior to the experiment. The rats were anesthetized and initially injected SC in the neck with either 50 mg/kg of CAP (10% Tween 80, 10% ethanol, 80% saline) or an equal amount of solvent for control rats. To prevent fatality from CAP-induced bronchospasm, the rats were placed in a chamber with an atmosphere of 95% OZ. 5% C02, and a mist of 0.75% isoproterenol. On the day of the experiment, bilateral cervical vagotomies were performed 1 h prior to, and atropine pretreatments (1 .O mg/kg, IP) were performed 15 min prior to the experiment.

0 CH,NH&- (Cl-4 ),-=43

No&amide

; nonanoyl-vanillylamide (NVA)

0

“3W

RO

\-,

CH,Nl&

(C&z I,-%

43

R= -CH,-FH-CH,-OH OH

Glyceryl nonivam~de (GLNVA) FIG.

I.

Chemical structures of capsaicin and its analogues.

METHOD

General Preparations Male Wistar rats weighing 250-350 g (provided by the Experimental Animal Center, Cheng-Kung National University Medical College, Tainan, Taiwan) were anesthetized with sodium pentobarbital (Nembutal, 50 mgfkg IP). Following tracheal cannulation, systemic arterial blood pressure, mean systemic arterial pressure, and heart rate were taken from a cannulated femoral artery. Then they were recorded by a pressure transducer (Gould, Model P50) connected to a pressure processor amplifier (Gould, Model 13-46 15-52) and displayed on a recorder (Gould, 8 1884402). The femoral vein was cannulated for IV injections and a retrograde cannulation was performed on a superficial epigastric artery for IA injections into the hind leg via the femoral artery. Body temperature was maintained at a rectal temperature of 37°C (f 1°C). The injection solutions of CAP and NVA were prepared using 1% ethanol and 1% Tween 80, and appropriate dilutions were made with saline. GLNVA was dissolved in 1% Tween 80 and 7% propylene glycol and diluted with normal saline. All other reagents, were prepared in normal saline immediately prior to use.

For intrathecal injection (IT), pairs of male Wistar rats weighing 250-350 g were anesthetized with urethane (1.25 g/ kg) administrated intraperitoneally. Each animal was placed in a stereotaxic head holder with the head flexed slightly forward. 1T injection of the substance P (SP) antagonist [D-Pro2, D-TQJ’.~]SP was made with a polyethylene catheter (8 cm, PE- IO) inserted into the suba~chnoid space of the spinal cord using an electric gear-driven syringe pump. The catheter was inserted through an incision in the cisterna magna, to the rostra1 edge of the lumbar enlargement at L5/L6. A SP antagonist (I 5 ~1) was delivered and followed by the administration of saline (10 ~1) at 15 pl/ min. CAP, NVA, or GLNVA was administered (IA) 7 min after delivery of the SP antagonist (6).

Each rat was immobilized in a David-Kopf stereotaxic instrument. The cerebellum was exposed after removing the skin and the occipital bone. The NTS coordinates were (reference to lamdar) P 5-6 mm, L/R 0.5-l mm, depth 6-7.5 mm. The injection sites in the NTS were conlirmed by responsiveness to Lglutamate. Decreases in blood pressure and heart rate were observed following microejection of 1% of L-glutamate into the NTS. All drugs were locally applied by pressure ejection from multibarreled micropipettes. This method of drug administration has previously been shown to be reproducible and linearly related to the duration and pressure of the drug ejection ( 18). In effect, the local pressure ejection dose can be expressed as the product of the ejection pressure (in psi) multiplied by the duration of the drug ejection (in seconds) or psi-s (8). Because of the relatively low barrel concentration of drug, there is little leakage of drug between ejection trials (! 8). The released volume of drug in a 50 psi.s dose is approximately 1O-J ~1 (29). At the end of expe~ment, the animal was sacrificed. The brain was removed and sectioned for histological confirmation of the area of drug application. Statistical Ana/,ysis Student’s t test for unpaired data, using significance levels of 0.05 and 0.01 for probability values (p) were applied to all the results. Litchfield and Wilcoxon method for evaluating doseeffect experiments (13) was implemented to estimate EC&‘s for CAP, NVA, and GLNVA doses as found in Table 1 and used throughout the text, Reagents Drugs used were: capsaicin, atropine, L-glutamate, and [DPro’, D-Trp7*9]-SP(Sigma, St. Louis, MO), nonivamide (T.C.1.).

CARDIOVASCULAR

EFFECTS

TABLE

OF GLYCERYL

1

BLOOD PRESSURE RESPONSES TO IV INJECTIONS OF CAPSAICIN, NONIVAMIDE, AND GLYCERYL NONIVAMIDE IN ANAESTHETIZED RATS

Effect A

Effect B

Efht C

120.7 -t 3.9 121.4 * 4.0 116.8 * 4.1 122.1 +_2.4

106.6 & S.O* 100.7 -C4.4* 57.4 -t- 4.61: 48.3 i: 7.1 f

(or effect C)$ (or effect C)$ 103.5 + 2.8* 125.2 t 6.7

70.2 * 1.8.f 56.2 k 4.0.f

130.6 -t 130.5 ? 120.5 + 115.2 +

123.7 rt 2.7 118.3 I: 3.O* 60.2 rt 2.6t 52.1 -t- 5.9 f

(or effect C)# (or effect C)# 107.2 * 6.7 127.3 * 4.8

78.0 + 4.3f 61.8 ? 3.5.f

CAP 0.1

I.o 10.0 100.0 NVA 0.1 1.0 10.0 100.0 GLNVA 0.i

1.0 10.0 loo.0

2.6 1.7 5.7 2.1

127.5 t 113.6 -t 101.7 -t 91.6 -t

135.0 r 1.9 130.4 c 3.1 135.0 * 4.8 138.2 _+4.9

After vagotomy, the vagus reflex response (effect A) following injection of CAP or NVA was not observed, but effects B and C were still present (Fig. 3). Vagotomy did not affect GLNVA (0.1 mg/kg) induced blood pressure and heart rate changes (Fig. 4). Following

Blood Pressure (mm Hgj COIIWOI

643

NONIVAMIDE

2-l 3.7* 5.2-l6.37

Values are expressed as means c SE (n = 8). *(p < 0.05) and -f(P r 0.0 1I asterisks indicate significant differences compared COcontrol, $ EA‘ectA and effect C were unditl&enriated from each other at lower

desensitization

pretreatment

with CAP prior to

administration of CAP and NVA (0. I m&kg), effect A was still observed but attenuated, however, both effect C of CAP as well as the monophasic hypotensive effect of GLNVA (0.1 mg/kg) disappeared entirely (Fig. 4). Peripheral Arterial Vasodi!ation Eflects

ofGLNVA

After retrograde epigastric injection of NVA ( LOrg/kg) into the femoral artery of male Wistar rats was found to induce only a single phase hypotensive effect (to 1LO.0+ 2.4 mm Hg from 138.3 t- 3.6 mm Hg) and a slight decrease in heart rate (to 346.7 & 13.0 beats/min from 360.0 -+ 9.1 beats/min). The triphasic blood pressure response to NVA, with its concurrent biphasic bradycardia, was only found to occur at a relatively high IA dosage (50 gg/kg). The triphasic blood pressure response to CAP was found to occur at a dosage more than 25 gg/kg. Equally an IA injection of GLNVA (0. I mg/kg) induced a monophasic hypotension (from 12 I .7 -+ 3.5 mm Hg to 8 1.7 f 4.8 mm Hg) similar to that induced by an IV injection, but the heart rate increased slightIy to 340.0 * 11.8 beats/min from 330.0 -(_I 1.0 beats/min (Fig. 5).

doses.

Glyceryl nonivamide (N-(4-o-glycerol-3-methoxy-benzyl)ivamide) was synthesized in our laboratory (4).

non-

RESULTS

Injection of CAP or NVA (10 rc.g/kgand 100 &kg) into the left femoral vein of male Wistar rats induced a triad of blood pressure changes, referred to as effects A, B, and C (Fig. 2 Table I). An initial reduction in blood pressure (effect A) was seen about 11 s after the injection. At 32 s after the injection, this reduction was followed by a rise in blood pressure to the original level or a level slightly higher than original bIood pressure (effect B). Finally, a second reduction in blood pressure (effect C) developed about 86 s after the injection. The reduction, however, was much more gradual and prolonged than the first. This triphasic blood pressure response was accompanied by a sharp decrease in heart rate, fast and slow bradycardia occurring concurrently with hypotensive effects A and C, respectively (Fig. 2). However, in contrast to CAP and NVA, injections of GLNVA (0.1, 1, 10, and 100 pg/kg) induced only a single phase hypotensive effect, emerging approximately 20 s after injection. For GLNVA, the decrease in heart rate was very moderate and no significant effect on respiration was observed (Fig. 2 and Table 1). The delayed fall in blood pressure (effect C) was analyzed to determine relative potency (20). The relative potency of NVA versus CAP is 0.36 and GLNVA versus CAP is 0.07. The hypotensive effects of those three compounds could be placed in the following order: CAP r NVA > GLNVA. Following pretreatment with an IP injection of atropine (1 .O mgfkg), the initial fall in biood pressure induced by CAP or NVA (0. I m&kg) was significantly inhibited (Fig, 3). However, neither effect C nor the monophasic hypotension induced by GLNVA (0.1 mg/kgf were affected (Fig. 4).

After pretreatment with an IT injection of [D-Pro’, D-TIJJ~*~]SP ( 1 nmol), hypotension resulting from CAP and NVA (10 pg/ kg, IA) was completely eliminated (Fig. 5). Retrograde epigastric IA injection of GLNVA (0.1 mg/kg) following IT pretreatment with SF antagonist resulted in a similar inhibition of its hypotensive effect, heart rate (10.2 t 6.9 beats/min against 7.5 & 4.5 beats/min) was found to decrease slightly and insignificantly (Fig. 5). The effect of pretreatment with the SP antagonist was found to be reversible as described by Bury and Mashford (3).

Unitateral micruejection ofCAP or NVA into the NTS produced a dose-dependent decrease in blood pressure and heart rate (Fig. 6). Simiiariy, when the solvent (1% Tween 80, 7% propylene glycol in normal saline) alone did not alter blood pressure and heart rate. The effects were almost immediate, peaking about 13 s after administration and persisting for about I min (Fig. 7). The hypotensive reaction to CAP and NVA were both reversible and reproducible. The maximal hypotensive effect and ECso of NVA (400 psi * s) are 30.3 4 12.3 mm Hg and 250 psi - s (Fig. 6).

FIG. 2. Elect ofW injection of0. I mg/kg capsaicin (CAP), noaivamide (WA), and glyceryi nonivamide (GLNVA) on blood pressure and heart rate with typical recordings.

644

YEH ET AL.

l

*

88 48 28 8 -2% -48 -66 -86

-68

E

0

: control

Lx9 : umgotom~

m:rtropino prrtrertinent !ZU:crprricin pretreatment

FIG. 3. Effect of IV injection of 0.1 mg/kg capsaicin and nonivamide on blood pressure

in control and in rats after various treatments. For exnlanation of different oretreatments see text. (A) injection of capsaicin. (B) injection of nonivamide. Middle traces show that original records of blood pressure and heart rate during IV injection of nonivamide. Vertical lines reoresent SE (n = 8). SineJe (D c 0.05) and double (P < 0.01) asterisks indicate signifi&t differences comparedto control

Hypotension from microejection of GLNVA into the NTS was also dose-dependent (Fig. 6). The potency and power of GLNVA were found to equal that of NVA and less than CAP. However, in contrast to CAP and NVA, GLNVA microejected at the NTS did not induce changes in heart rate. The maximum dose of GLNVA (400 psi * s) evoked a slight bradycardia, but it was not significantly different from the control (Fig. 7). DISCIJSSION

The blood pressure changes induced by IV administration of CAP and NVA were triphasic: (a) an initial fall with brady-

cardia and aponea; (b) an intermediate rise, and (c) a second, more gradual, fall of the rat’s blood pressure. A detailed analysis of the mechanisms underlying these effects of CAP has been carried out by Donnerer and Lembeck (5). They concluded that effect A was absent after bilateral vagotomy, that effect C remained unchanged after v~otomy but was absent after neonatal CAP pretreatment, and that effect B was not diminished after vagotomy or despinalization and was augmented in rats treated neonatally with CAP. Thus, it is proposed that both effect A and C caused by a reflex response of CAP-sensitive small diameter afferent fibers, and effect B resulted mainly from a direct short

CARDIOVASCULAR

EFFECTS OF GLYCERYL

0 m

: control : UrQotomy

645

NONIVAMIDE

N : rtrcpinm 9:crprricin

pr-tr=otm=nt prltrrrtmrnt

FIG. 4. Effect of IV injectionof0. I mgjkg glyceryl nonivamide on blood pressure in control and in rats after various treatments. For explanation of different pretreatments see text. Vertical lines represent SE (n = 8). Single (p < 0.05) and double (p -=z0.0 1)asterisks indicate significant differences compared to control.

vasoconstriction by CAP. The responses to CAP and NVA by rats pretreated with CAP and bilateral cervical vagotomies were almost identical to the responses elicited in Donnerer’s study on CAP (5). However, in the present experiments the initial fall in blood pressure (effect A) following injection of either NVA

or CAP was found to be diminished by atropine and CAP pretreatment. An efferent cholinergic mechanism would thus seem to be involved in effect A. This is contrary to the findings of Donnerer et al. (5) for CAP, in which effect A was found to remain unchanged after treatment with atropine and a cholinergic mechanism was therefore excluded. Therefore, it is possible that the effect A was mediated by vagal reflex, choline& mechanisms and CAP-sensitive nerves. An increase of effect B by IV CAP in rats pretreated with SC CAP may be due to the degeneration of their sensory nerve or the depletion of SP and then the relief of parasympathetic stimulation. So we also suggest that the peripheral vasocontraction of CAP facilitates this increase and contributes to effect B of CAP. The results of the present study confirms that the cardiovascular response to peripherally administered GLNVA is different from that to CAP and NVA. First, both IV and IA injection of GLNVA resulted in a monophasic blood pressure response but did not significantly affect heart rate. Second, this depressor response remained the same following pretreatment with bilateral

vagotomy or IP injection of atropine. However, pretreatment with CAP in order to degenerate sensory-c fibers led to the disappearance of the hypotensive effect of GLNVA. Fourth, IT pretreatment with SP antagonist was found to inhibit the depressor response to GLNVA and only marginally affected heart rate. Because CAP and NVA release SP from the upper dorsal horn of the rat spinal cord (I), neonatal treatment with CAP and NVA reduce the content of SP-like immunoreactivity in the dorsal spinal cord (20). The fall in blood pressure (effect C) caused by IV injection of CAP and NVA has been shown to reflect the stimulation of peripheral afferent neurons containing SP (20). Furthermore, acute administration of CAP or NVA into the thoracic aorta of guinea pig in vitro produced both transient smooth muscle relaxation and then contraction, but administration of GLNVA produced only relaxation (Chen et al., unpublished data). It is suggested that GLNVA induces its vasodilatory effects by the same mechanism that CAP and NVA produce effect C, that is, by selectively stimulating peripheral sensory C-fibers to release SP (5). Recent reviews summarized the evidence indicating that CAP is a selective agent affecting primary afferent neurons (10,15). CAP-sensitive primary sensory neurons are capable of releasing transmitters from their peripheral endings, thus conferring them with ‘efferent’ functions (16). Several neuropeptides, including

646

YEH

NW

CAP

ET AL.

GLNUA

FIG. 5. Effect of IT injection of I nmol of substance P antagonist-[D-Pro’. D-Trp’,‘]-SP on the blood pressure responses to IA injections of capsaicin (CAP. 10 &kg), nonivamide (NVA, 10 pg/kg) and glyceryl nonivamide (GLNVA, 0.1 mg/kg). All values after pretreatment SP antagonist differ significantly (’ p < 0.05; ‘*p < 0.01) from NVA or GLNVA alone. Each bar represents the means + SE (n = 8).

tachykinins and calcitonin gene-related peptide (CGRP), are released in the peripheral and central nervous system in this way. In this study, pretreatment with a SP antagonist inhibited the hypotension resulting from CAP, NVA, and GLNVA and reversed the changes in heart rate associated with each. [D-Pro’, D-TQJ~,~]-SP specifically blocks the effect of exogenously applied SP as well as SP which is endogenously released from within the central nervous system. This suggests that antidromic hypotension might be induced by a peripheral release of the SP that

50

40

30

20 10

0

I

A-A: O-O: 0-O:

CAP

NVA GLNVA

mediates centripetal transmission of impulses from sensory neurons ( 12). SP has been immunohistochemically localized in a distinct population of unmyelinated primary sensory neurons, and it has been considered the primary sensory transmitter involved in the stimulation of CAP-sensitive primary afferents ( 19). In the retrograde epigastric injections of CAP, NVA, and GLNVA in this study, the depressor reflex response to GLNVA was eliminated and converted to a minor pressor reflex in SPantagonist-pretreated rats. Therefore, GLNVA sensitive nerves seem to be involved in some way with CAP-containing afferent nerves. Unilateral microejection of CAP and NVA into the NTS evoked a dose-dependent hypotension and bradycardia. GLNVA applied to the same sites produced similar changes in blood pressure but failed to affect the heart rate. The cardiovascular responses produced by the administration of CAP, NVA, or GLNVA were drug-specific, because no cardiovascular changes were induced by the solvent alone. Furthermore, because the responses are both reversible and reproducible, they are unlikely

t

I 0

CAP

100

NVA

GLNVA

? 200

300

400

5 00

Dose (psi. set)

6. Dose-response curve of CAP. NVA, and GLNVA-induced changes of blood pressure. CAP, NVA, and GLNVA were applied locally into the NTS. NVA-induced response is not different from that of GLNVA. CAP-induced response is different from that of GLNVA ‘11 < 0.05: **p < 0.0 I. Data were expressed as means + SE (n = 8).

FIG. 7. Different cardiovascular reactions induced by CAP, NVA, and GLNVA (400 psi.s). CAP and NVA locally applied to NTS produced hypotension and bradycardia; GLNVA only elicited hypotension.

CARDIOVASCULAR

EFFECTS OF GLYCERYL

641

NONIVAMIDE

to arise from tissue damage. The NTS plays a major role in regulating blood pressure. It receives direct input, via the vagus and glossopharyngeal nerves, from baroreceptors in the carotid sinus and aortic arch, activation of which lead to a decrease in blood pressure (19). GLNVA, like NVA and CAP, caused a marked effect on blood pressure when applied locally to the NTS but without any significant heart rate changes. The hypotensive reaction induced by CAP or its analogues may be related to SP. Immunohistochemical studies have revealed dense SP-positive nerve terminals in the NTS (24). Because CAP releases SP from primary afferent fibers (25) neonatal treatment with CAP reduces the content of SP-like immunoreactivity in the area of the NTS in rats (24). Local application of SP into the NTS has been found to produce hypotension and bradycardia (14). It is known that replacement or chemical modification of the free phenolic hydroxyl group of CAP leads to a marked decrease or loss of pungency in CAP and its analogues (1,22,23). The results of the present study indicate that the potency of the hypotensive effect of GLNVA is also decreased and that the initial vagus reflex and effect B are abolished. The structural modification of NVA or CAP, leading to the absence of these untoward effects, encourages us to look at the application of NVA or CAP analogues such as GLNVA in the therapy of human diseases. The development of drugs capable of controlling the sensory-

efferent functions of the CAP-sensitive sensory neurons represents a new and very promising area of research for pharmacological treatment of cardiovascular diseases and hyperalgesia (4). NVA was previously found to produce a triphasic hypotensive response (3 I), however, in the present study, GLNVA only produced a only monophasic blood pressure change when administered intravenously. Peripheral artery vasodilation after epigastric retrograde IA injection of GLNVA (0.1 mg/kg) reveal more hypotensive effects than NVA (10 wg/kg) were inhibited by SP antagonist. Furthermore, microejection of CAP and NVA into the NTS elicited hypotension and bradycardia, while GLNVA evoked only a decrease in blood pressure and not in heart rate. These findings suggest that the cardiovascular changes induced by GLNVA are different from those induced by NVA or CAP. It is concluded that (a) GLNVA caused only a monophasic depressor response and does not produce the untoward vagus reflex and vasocontractile activity that are associated with CAP or NVA, and (b) GLNVA may selectively activate peripheral perivascular small diameter C-fiber sensory nerves, as also in the case with CAP and NVA. ACKNOWLEDGEMENTS

This work was supported by research grants from National Science Council of R.O.C. (NSC 79-0412-B037-5 I and NSC 80-0115 -C-O 16-03).

REFERENCES 1. Bucsics, A.; Lembeck, F. In vitro release of substance P from spinal cord slices by capsaicin congeners. Eur. J. Pharmacol. 71: 71-77; 1981. 2. Buck, S. H.; Burks, T. F. The neuropharmacology of capsaicin: Review of some recent observations. Pharmacol. Rev. 38: 179- 226; 1986. 3. Bury, R. W.; Mashford, M. L. Cardiovascular effect of synthetic substance P in several species. Eur. J. Pharmacol. 45: 335-340: 1977. 4. Chen, I. J.; Yang, J. M.; Yeh, J. L.; Wu, B. N.; Lo, Y. C.; &en, S. J. Hypotensive and antinociceptive effects of ether-linked and relatively nonpungent analogues of N-nonanoyl vanillylamide. Eur. J. Med. Chem. 27: 187-192; 1992. 5. Donnerer, J.; Lembeck, F. Analysis of the effects of intravenously injected capsaicin in the rat. Naunyn-Schmiedeberg’s Arch Pharmacol. 320: 54-57; 1982. 6. Donnerer, J.; Lembeck, F. Capsaicin-induced reflex fall in rat blood pressure is mediated by afferent substance P-containing neurones via a reflex center in the brain stem. Naunyn-Schmiedeberg’s Arch Pharmacol. 324: 293-295; 1983. 7. Fuiii. T.: Ohbuchi. Y.: Takahashi. S.: Sakurada. T.: Sakurada. S.: Ando, R.; Kisara, K. Studies on the hypothermic response of cap: saicin and its analogue in mice. Arch. Int. Pharmacodyn. 280: 165176; 1986. 8. Gerhardt, G. A.; Palmer, M. R. Characterization of the techniques of pressure ejection and microiontophoresis using in vivo electrochemistry. J. Neurosci. Meth. 22: 147-159; 1987. 9. Hayes, A. G.; Oxford, A.; Reynolds, M.; Shingler, A. H.; Skingle, M.; Smith, C.; Tyers, M. B. The effects of a series of capsaicin analogues on noniception and body temperature in the rat. Life Sci. 34: 1241-1248; 1984. 10. Holzer, P. Capsaicin: Cellular targets, mechanisms of action, and selectivity for thin sensory neurons. Pharmacol. Rev. 43: 143-201; 1991. I I. Jan&, G.; Hokfelt, T.; Lundberg, J. M.; Kiraly, E.; Hal&z, N.; Nillson, G.; Terenius, L.; Rehfeld, J.; Steinbusch, H.; Verhofstad, A.; Elde, R.; Said, S.; Brown, M. Immunohistochemical studies on effect of capsaicin on spinal and medullary peptide and monoamine neurons using antisera to substance P, gastrin, CCK, somatostatin,

12.

13. 14. 15. 16.

17. 18. 19. 20.

21.

22.

23.

VIP, enkephalin, neurotensin and 5-hydroxytryptamine. J. Neurocytol. IO: 963-980; 1981. Lembeck, F.; Donnerer, J. Time course of cap&in-induced functional impairements in comparison with changes in neuronal substance P content. Naunnyn-Schmiedeberg’s Arch Pharmacol. 3 16: 240-243; 198 1. Litchfield, J. L.; Wilcoxon, F. A simplified method evaluating doseeffect experiments. J. Pharmacol. Exp. Ther. 96: 99-113; 1949. Lukovic, L.; de Jong, W.; de Wied, D. Cardiovascular effects of substance P and capsaicin microinjected into the nucleus tractus solitarii of the rat. Brain Res. 422: 3 12-3 18; 1987. Maggi, C. A. Capsaicin and primary afferent neurons: From basic science to human therapy? J. Auton. Nerv. Syst. 33: I- 14; 1991. Ma&, C. A.; Patacchini, R.; Santicioli, P.; Giuliani, S.; Bianco, E. D.; Geppetti P.; Meli, A. The ‘efferent’ function of capsaicin-sensitive nerves: Ruthenium Red discriminates between different mechanisms of activation. Eur. J. Pharmacol. 170: 167-177; 1989. Monsereenusom, Y.; Kongsamut, S.; Pezalla, P.D. Capsaicin DD A literature survey. CRC Crit. Rev. Toxicol. 10: 321-339; 1982. Palmer, M. R.; Wuerthele, S. M.; Hoffer, B. J. Physical and physiological characteristics of micropressure ejection of drugs from multibarreled pipettes. Neuropharmacol. 19: 93 l-938; 1980. Pernow, B. Substance P. Pharmacol. Rev. 35: 85-141; 1983. Skotitsch, G.; Donnerer, J.; Lembeck, F. Comparison of nonivamide and capsaicin with regard to their pharmacokinetics and effects on sensory neurons. Arzneim.-Forsch./Drug Res. 34: 154- 156; 1984. Szallasi, A.; Blumberg, P. M. Resiniferatoxin, a phorbol-related diterpene, acts as an ultrapotent analog of capsaicin, the irritant constituent in red pepper. Neuroscience 30: 5 15-520; 1989. Szolcdnyi, J.; Jancs&ocaute;-Gabor, A. Sensory effects of capsaicin congeners. I. Relationship between chemical structure and painproducing potency of pungent agents. Arzneim.-Forsch./Drug Res. 25: 1877-1881; 1975. Szolcsanyi, J.; Jancs&Gabor, A. Sensory effects of capsaicin congeners. II. Importance of chemical structure and pungency in desensitizing activity of capsaicin-type compounds, Anneim.-Forsch./ Drug Res. 26: 33-37; 1976.

648

24. Takano, Y.; Nagashima, A.; Kamiya, H.; Kurosawa, M.; Sato, A. Well-maintained reflex responses of sympathetic nerve activity to stimulation of baroreceptor, chemoreceptor and cutaneous mechanoreceptors in neonatal capsaicin-treated rats. Brain Res. 445: 188192; 1988. 25. Theriault, E.; Otsuka, M.; Jessell, T. Capsaicin-evoked release of substance P from primary sensory neurons. Brain Res. 170: 209213; 1979. 26. Toda, N.; Usui, H.; Nishino, N.; Fujiwara, M. Cardiovascular effects of capsaicin in dogs and rabbits. J. Pharmacol. Exp. Ther. I8 1:5 12521; 1972. 27. Toh, C. C.; Lee, T. S.; Kiang, A. K. The pharmacological actions of capsaicin and analogues. Br. J. Pharmacol. IO: 175-182; 1955.

YEH

ET AL

28. Virus, R. M.; Gebhart, G. F. Pharmacologic actions of capsaicin Apparent involvement of substance P and serotonin. Life Sci. 25: 127331284: 1979. 29. Wang, Y.; Kim, M. B.; Palmer, M. R. Interactions of metaphit with phencyclidine and sigma agonist actions in rat cerebellum: Determination of specificity and selectivity. J. Pharmacol. Exp. Ther. 24 I : 321-327: 1986. 30. Winning, A. J.; Hamilton, R. D.; Shea. S. A.: Guz, A. Respiratory and cardiovascular effects of central and peripheral intravenous injections of capsaicin in man: Evidence for pulmonary chemo-sensitivity. Chn. Sci. 7 I: 5 19-526; 1986. 3 I, Yeh, J. L.; Chen. 1. J. Cardiovascular effect of nonivamide succinate. Kaohsiung J. Med. Sci. 6: 10-20: 199 1.