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Spreading depression in hippocampus and neocortex of rats induced by ACTH1–24
Neuroscience Letters, 5 (1977) 189--192 © Elsevier/North-Holland Scientific Publishers Ltd.
SPREAD][NG D E P R E S S I O N IN H I P P O C A M P U S RATS INDUCED BY ACTHI-24
189
AND NEOCORTEX
OF
LISANNE J A K O B A R T L and JOSEPH P. H U S T O N *
lnstftute of Pharmacology, University of Ziirich, Gloriastrasse 32, 8006 Ziirich (Switzerland) (Received May 5th, 1977) (Accepted May 11th, 1977)
SUMMARY
Microinjection of synthetic ACTH~_24 solution into the neocortex or hippocampus of anesthetized rats elicitedwaves of spreading depression in both structures.The average effectivedoses for elicitingspreading depression were 6.22 ~g (range 2.5--15.0 ~g) in neocortex and 1.38 ~g (range 0.24--2.88 ~g) in hippocampus. This suggests that some of the behaviors elicited by intracranial injection of ACTH may be d,~e to hippocampal {and possibly also neocortical) spreading depression.
Intracranial injection of various peptides, such as ACTHI_24, elicits behaviors such as penile erections, grooming and the 'stretching and yawning syndrome' (SYS) in various species. Among the peptides with this characterist,ic are ACTH- and MSH-like pepfides [1,2,4--8], and other synthetic neuropeptides, such as lipotropin fragments (LPH61-gr) [6]. These same behaviors (in addition to feeding and drinking} are also induced by neocorfical and hippocampal spreading depression (SD), particularly after repeated waves of SD [9--12]. It is possible, therefore, that either SD mimics the hormonal effects or that these pepfides elicit spreading depression, which, in turn, induces the various behaviors. Accordingly, the present study sought to determine whether ACTHl_24 could elicit SD in the hippocampus and neocortex of rats. Nineteen male Sprague-Dawley rats of the SIV 50 strain (Tierspital Zfrich), weighing 4 5 0 - 5 5 0 g, were tested with freshly prepared solutions of/~ 1-24corticotrophin (Synacthen, Ciba-Geigy). The animals were anesthetized with 50 mg]kg pentobarbital. For cortical DC and EEG recording with calomel electrodes, holes of I mm diameter were bilaterally drilled 3 mm anterior to bregraa and 2 mm lateral from the midline. For cortical ACTH administration *Author to whom reprint requests should be sent.
190
trephine holes (3 mm diameter) were bilaterally placed 3--6 mm posterior to bregma end 2--5 mm lateral from the midline in 7 rats. Two animals were implanted bilaterally (-3.{), 2.0, 0.5) with 16 mm long 22-gauge stainless steel cannula guides (0.71 m m o,d., 0 , 4 1 m m i.d.). The coordinates were referenced to the bregma (antenor-postenor,/!a~ral/ventral) with bregma and lambda being on a horizontal plane. For hippocampal DC and EEG recording 10 animals were implanted bilaterally (-6.0, 4.0, 4.5 o r - 3 . 5 , 2.0~ 3.0) with glass capillaries (3°4 mm o.d., 1.8 m m i.d.) filled with physiological saline. In addition, cortical DC slow potential changes and EEG were recorded as described above. Peptide solutions were injected through cannulae implanted bilaterally into the hippocampus ( - 3 . 5 , 2.0, 3.0 o r - 6 . 0 , 4.0, 4.5) of
I0 animals (Fig. !). Cortical and hippocampal slow potential changes (SPC) and E E G were registered by four differentialamplifiers (Tektronix, types 2 6 A 2 and A M 502), and recorded with a polygraph. After the operation DC and EEG baselines were recorded for 30--60 min prior to administration of peptide. At least 60 rain elapsed between applications of ACTH, which was administered to the right and left hemispheres, in true. For co~!cal peptide administration dissolved ACTH of various concentrations (the volume of injected solution ranging between 0.6 and 2.2 ~1) was either applied onto the exposed durae through the trephine openings in 7 rats, or was injected through the cortical cannulae in 2 animals. For hilc,pocampal injections peptide solutions at various concentrations (volume ranged from 0.1 to 2.5 ~1) were used, and hippocampal and cortical SPCs and EEG were recorded over a period for at least 30 rain pre- and post-injection. After the experiments the brains were perfused, removed, sectioned, stained and examined to ensure correct placement of cannulae and electrodes. Cortical spreading depression. Cortical SD was elicited in all 9 rats injected with ACTH onto or into neocortex (see Fig. I for example). Initial doses were arbitrarily fixed and had to be lowered in 3 cases, whereas in 6 cases the initial dose was too low. A total of 24 positive SD trials were recorded. In 87.5% of the trials only one wave was recorded after administration of ACTH (range 1 to 3 waves). The mean effective dose for generating cortical SD was found to be 6.22/~g (range 2.5 to 15 ~g) (contained in ~ {).6% solution). The mean volume of applied solutions was 1.3 #l (range 0.6 to 2.2 ~l). In all 9 rats application of the individual 'minimum' dose elicited only one wave of SD. Hippoeampal spreading depression. A total of 24 positive hippocampsl SD trials were recorded in the 10 rats tested (see Fig. 1). An injection of ACTH generated, on average; 2.7 waves (range I to 8 waves) within a 30-min testing session. In 4 trialsin 3 animals afterdischargeswere recorded; however, at doses (6.4--1(,~g) that were far above m i n i m u m dose~. Cortical S D after hippocampal injection (due to solution running up cannu][a guide to neocortex) ~,as recorded only once. The mean concentration of 'effective'doses taken from the I0 rats was 1.38 ~g A C T H (range 0.24 to 2.88/~g). A 0.6% solution was most effective.Doses below 1.76 ~g elicited1.6 waves on average (n = 5), whereas doses beyond 1.76 ~g (n = 5) elicited3.8 waves, indicating that the
191
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number of hippocampal SD waves was dose-dependent. The initial doses had to be lowered in 4 cases and increased in 6 cases to reach individual 'minimum' doses for the generation of hippocampal SD. Hence, ACTH~_24 elicRs spreading depression in both hippocampus and neocortex of rats. The-relatively lower threshold for hippocampal compared to neocortical SD covcesponds to the threshold differences (about 5 times higher threshold concentration in neocortex) obtained with KC1 in these structures [3]. Our results indicate that Some of the behaviors, such as SYS, shaking and penile erections, observed after intracranial injections of ACTH~_24 (and other peptides) could be aftereftects of spreading depression. ACKNOWLEDGEMENT
This study was supported by the Swiss National Science Foundation Grant No. 3.6610.75. REFERENCES
1 Bertolini, A., Gessa, G.L. and Ferrari, W., Penile erection and ejaculation: a central effect of ACTH-like peptides in mammals. In M. Sandler and G.L. Gessa (Eds.), Sexual Behavior: Phaimacology and Biochemistry, Raven Press, New York, 1975, pp. 247--257. 2 Bertolini, A., Gessa, G.L., Vergoni, W. and Ferrari, W., Induction of sexual excitement with intraventricular ACTH: permissive role of testosterone in the male rabbit, Life Sci., 7 (1968) 1203--1206. 3 Buret, J., Bure~ov~, O. and K~iv~nek, J., The Mechanism and Application of Le~o'~ Spreading Depression of Electroencephalographic Activity, Academic Press, New York, 1974. 4 F~n'ari, W., Gessa, G.L. and Vargiu, L., Behavioral effects induced b y intracisternally injected ACTH and MSH, Ann. N,Y. Acad. Sci., 104 ~1963) 330--343. 5 Gesr~, G,L,, Vargiu, L. and Ferrari, W., Stretchings and yawnings induced by adrenocorticotrophic h o ~ o n e , Nature (Lond.), 211 (1966) 426--427. 6 Gispen, W.H., Wiegant, V,M., Bradbury, A.F., Hulme, E.C, Smyth, D.G. and Snell, C . R , Induction of excessive grooming in the rat by fragments of lipotropin, Nature (Lond.), 26~ (1976) 794--795. 7 Gispen, W.H., Wiegant, V.M., Greven, H.M. and de Wied, D., The induction of excessive grooming in the rat by intraventricular application of peptides derived from ACTH: structure-activity studies, Life Sci,, 17 (1975~ 645--652. 8 Haun, C.K. and Haltmeyer, G.C., Effects of an intraventricular injection of synthetic ACTH on plasma testosterone, progesterone and LH-~evelsand on sexual behavior in male and female rabbits, NeuroendocrinolGgy, 19 (1975) 201--213. 9 Huston, J.P., Yawning and penile erections induced in rats by cortical spreading depression, Nature (Lond.), 232 (1971) 274--275. 10 Huston, J.P~ and Buret, J,, Drinking and eating elicited by cortical spreading depression, Science, 169 (i970) 702--704. 11 Huston, J.P,, Siegfried, B., Ornstein, K., Waser, P.G. and Borb~ly, A.A., Eating elicited by spreading depression or electrical stimulation in the hippocampus and neocortex: a common cause, Brain Res., 78 (1974) 164--168. 12 Siegfried, B. and Huston, J.P., Properties of spreading depression induced consumatory behavior in rats~ Physiol. Behav., (1977) in press.
SPREAD][NG D E P R E S S I O N IN H I P P O C A M P U S RATS INDUCED BY ACTHI-24
189
AND NEOCORTEX
OF
LISANNE J A K O B A R T L and JOSEPH P. H U S T O N *
lnstftute of Pharmacology, University of Ziirich, Gloriastrasse 32, 8006 Ziirich (Switzerland) (Received May 5th, 1977) (Accepted May 11th, 1977)
SUMMARY
Microinjection of synthetic ACTH~_24 solution into the neocortex or hippocampus of anesthetized rats elicitedwaves of spreading depression in both structures.The average effectivedoses for elicitingspreading depression were 6.22 ~g (range 2.5--15.0 ~g) in neocortex and 1.38 ~g (range 0.24--2.88 ~g) in hippocampus. This suggests that some of the behaviors elicited by intracranial injection of ACTH may be d,~e to hippocampal {and possibly also neocortical) spreading depression.
Intracranial injection of various peptides, such as ACTHI_24, elicits behaviors such as penile erections, grooming and the 'stretching and yawning syndrome' (SYS) in various species. Among the peptides with this characterist,ic are ACTH- and MSH-like pepfides [1,2,4--8], and other synthetic neuropeptides, such as lipotropin fragments (LPH61-gr) [6]. These same behaviors (in addition to feeding and drinking} are also induced by neocorfical and hippocampal spreading depression (SD), particularly after repeated waves of SD [9--12]. It is possible, therefore, that either SD mimics the hormonal effects or that these pepfides elicit spreading depression, which, in turn, induces the various behaviors. Accordingly, the present study sought to determine whether ACTHl_24 could elicit SD in the hippocampus and neocortex of rats. Nineteen male Sprague-Dawley rats of the SIV 50 strain (Tierspital Zfrich), weighing 4 5 0 - 5 5 0 g, were tested with freshly prepared solutions of/~ 1-24corticotrophin (Synacthen, Ciba-Geigy). The animals were anesthetized with 50 mg]kg pentobarbital. For cortical DC and EEG recording with calomel electrodes, holes of I mm diameter were bilaterally drilled 3 mm anterior to bregraa and 2 mm lateral from the midline. For cortical ACTH administration *Author to whom reprint requests should be sent.
190
trephine holes (3 mm diameter) were bilaterally placed 3--6 mm posterior to bregma end 2--5 mm lateral from the midline in 7 rats. Two animals were implanted bilaterally (-3.{), 2.0, 0.5) with 16 mm long 22-gauge stainless steel cannula guides (0.71 m m o,d., 0 , 4 1 m m i.d.). The coordinates were referenced to the bregma (antenor-postenor,/!a~ral/ventral) with bregma and lambda being on a horizontal plane. For hippocampal DC and EEG recording 10 animals were implanted bilaterally (-6.0, 4.0, 4.5 o r - 3 . 5 , 2.0~ 3.0) with glass capillaries (3°4 mm o.d., 1.8 m m i.d.) filled with physiological saline. In addition, cortical DC slow potential changes and EEG were recorded as described above. Peptide solutions were injected through cannulae implanted bilaterally into the hippocampus ( - 3 . 5 , 2.0, 3.0 o r - 6 . 0 , 4.0, 4.5) of
I0 animals (Fig. !). Cortical and hippocampal slow potential changes (SPC) and E E G were registered by four differentialamplifiers (Tektronix, types 2 6 A 2 and A M 502), and recorded with a polygraph. After the operation DC and EEG baselines were recorded for 30--60 min prior to administration of peptide. At least 60 rain elapsed between applications of ACTH, which was administered to the right and left hemispheres, in true. For co~!cal peptide administration dissolved ACTH of various concentrations (the volume of injected solution ranging between 0.6 and 2.2 ~1) was either applied onto the exposed durae through the trephine openings in 7 rats, or was injected through the cortical cannulae in 2 animals. For hilc,pocampal injections peptide solutions at various concentrations (volume ranged from 0.1 to 2.5 ~1) were used, and hippocampal and cortical SPCs and EEG were recorded over a period for at least 30 rain pre- and post-injection. After the experiments the brains were perfused, removed, sectioned, stained and examined to ensure correct placement of cannulae and electrodes. Cortical spreading depression. Cortical SD was elicited in all 9 rats injected with ACTH onto or into neocortex (see Fig. I for example). Initial doses were arbitrarily fixed and had to be lowered in 3 cases, whereas in 6 cases the initial dose was too low. A total of 24 positive SD trials were recorded. In 87.5% of the trials only one wave was recorded after administration of ACTH (range 1 to 3 waves). The mean effective dose for generating cortical SD was found to be 6.22/~g (range 2.5 to 15 ~g) (contained in ~ {).6% solution). The mean volume of applied solutions was 1.3 #l (range 0.6 to 2.2 ~l). In all 9 rats application of the individual 'minimum' dose elicited only one wave of SD. Hippoeampal spreading depression. A total of 24 positive hippocampsl SD trials were recorded in the 10 rats tested (see Fig. 1). An injection of ACTH generated, on average; 2.7 waves (range I to 8 waves) within a 30-min testing session. In 4 trialsin 3 animals afterdischargeswere recorded; however, at doses (6.4--1(,~g) that were far above m i n i m u m dose~. Cortical S D after hippocampal injection (due to solution running up cannu][a guide to neocortex) ~,as recorded only once. The mean concentration of 'effective'doses taken from the I0 rats was 1.38 ~g A C T H (range 0.24 to 2.88/~g). A 0.6% solution was most effective.Doses below 1.76 ~g elicited1.6 waves on average (n = 5), whereas doses beyond 1.76 ~g (n = 5) elicited3.8 waves, indicating that the
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number of hippocampal SD waves was dose-dependent. The initial doses had to be lowered in 4 cases and increased in 6 cases to reach individual 'minimum' doses for the generation of hippocampal SD. Hence, ACTH~_24 elicRs spreading depression in both hippocampus and neocortex of rats. The-relatively lower threshold for hippocampal compared to neocortical SD covcesponds to the threshold differences (about 5 times higher threshold concentration in neocortex) obtained with KC1 in these structures [3]. Our results indicate that Some of the behaviors, such as SYS, shaking and penile erections, observed after intracranial injections of ACTH~_24 (and other peptides) could be aftereftects of spreading depression. ACKNOWLEDGEMENT
This study was supported by the Swiss National Science Foundation Grant No. 3.6610.75. REFERENCES
1 Bertolini, A., Gessa, G.L. and Ferrari, W., Penile erection and ejaculation: a central effect of ACTH-like peptides in mammals. In M. Sandler and G.L. Gessa (Eds.), Sexual Behavior: Phaimacology and Biochemistry, Raven Press, New York, 1975, pp. 247--257. 2 Bertolini, A., Gessa, G.L., Vergoni, W. and Ferrari, W., Induction of sexual excitement with intraventricular ACTH: permissive role of testosterone in the male rabbit, Life Sci., 7 (1968) 1203--1206. 3 Buret, J., Bure~ov~, O. and K~iv~nek, J., The Mechanism and Application of Le~o'~ Spreading Depression of Electroencephalographic Activity, Academic Press, New York, 1974. 4 F~n'ari, W., Gessa, G.L. and Vargiu, L., Behavioral effects induced b y intracisternally injected ACTH and MSH, Ann. N,Y. Acad. Sci., 104 ~1963) 330--343. 5 Gesr~, G,L,, Vargiu, L. and Ferrari, W., Stretchings and yawnings induced by adrenocorticotrophic h o ~ o n e , Nature (Lond.), 211 (1966) 426--427. 6 Gispen, W.H., Wiegant, V,M., Bradbury, A.F., Hulme, E.C, Smyth, D.G. and Snell, C . R , Induction of excessive grooming in the rat by fragments of lipotropin, Nature (Lond.), 26~ (1976) 794--795. 7 Gispen, W.H., Wiegant, V.M., Greven, H.M. and de Wied, D., The induction of excessive grooming in the rat by intraventricular application of peptides derived from ACTH: structure-activity studies, Life Sci,, 17 (1975~ 645--652. 8 Haun, C.K. and Haltmeyer, G.C., Effects of an intraventricular injection of synthetic ACTH on plasma testosterone, progesterone and LH-~evelsand on sexual behavior in male and female rabbits, NeuroendocrinolGgy, 19 (1975) 201--213. 9 Huston, J.P., Yawning and penile erections induced in rats by cortical spreading depression, Nature (Lond.), 232 (1971) 274--275. 10 Huston, J.P~ and Buret, J,, Drinking and eating elicited by cortical spreading depression, Science, 169 (i970) 702--704. 11 Huston, J.P,, Siegfried, B., Ornstein, K., Waser, P.G. and Borb~ly, A.A., Eating elicited by spreading depression or electrical stimulation in the hippocampus and neocortex: a common cause, Brain Res., 78 (1974) 164--168. 12 Siegfried, B. and Huston, J.P., Properties of spreading depression induced consumatory behavior in rats~ Physiol. Behav., (1977) in press.