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CRF stimulation of synaptosomal tyrosine hydroxylase activity in mouse striatum: possible role of phospholipid hydrolysis
-I there was a global decrease in 2-DG uptake from 2.16 f 0.03 (n = 6) in n = 5) in animals injected with ET-l (P -z 0.0001; F = 21.8; ANOVA). Of the 53 effects of ET-1 (Scheffe test P -z 0.05) were seen in only 4 regions (Table 1).
in brain regions following the i.c.v. administration of saline or ET-1 ( * P < 0.05 values are
1.9Of0.06 2.13*0.07 1.79kO.02 1.82f0.08
2.16f0.08 2.46*0.04 2.34 + 0.04 2.16f0.01
* * * *
n conclusion, i.c.v. ET-I m fied 2-DG uptake in distinct brain regions. The dissociation of the effects of i.v. and stration of ET-I for direct rather than vascular effects of ET-1 on neuronal activity and support a i.c.v. aa ulator of neuronal function. roIe for
hxx.
_ (1989) P.N.NA.S. In press. CR et al. (1989) Newosci. Let. 97, 276-279. ff, L et al. (1977) J. Neurachem.28,8%-916.
Qlianas
MC.
and On&
P.
Department of Neurosciences, Universiv of Cagliari, via Porcell4, 09124 Cagliari, Italy Corticotropin-releasing factor
(CRF) is considered to function as a neurotransmitter/neuromodulator in different tbalamic pathways of the CNS (Aguilera et al., 1987) We have observed that this peptide is a potent f tyrosine hydroxylase (TII) activity of rat and mouse striatal synaptosomes (Olianas and Onali, 1988; activity was assayed in extracts prepared by centrifugation and sonication of mouse striatal synaptosomes ed with the peptide. In mouse striatum, CRF maximally increases the enzyme activity by 60 (p < 0.001). as a function of low concentrations of the pterin cofactor D,L-dmethyl-5,6,7,8-tetrato 0.4 mM), the stimulatory effect of CRF consisted in an increase of the app. V,,,, of the enzyme form with high affinity for the cofactor. The CRF response occurred at nanomolar concentrations of the ), was significantly antagonized by the CRF receptor antagonist a-helical CRF 9-41 (Ki 120 eked by sauvagine (EC 50 5 nM) and urotensin I (EC 50 10 nM), two peptides homologous to CRF. n of synaptosomal TH activity displayed a marked dependence on extracellular Ca*+ concentrain a Ca+-free medium and maximal at about 0.5 mM extracellular free Ca*+. Moreover, the CRF d by polymyxin B, a protein kinase C inhibitor. Neomycin, an aminoglycoside which binds to ysis of phoshoinositides, maximally reduced the CRF-stimulated TH activity by 60% with an IC ue of about 0.15 mM. Under similar experimental conditions, neomycin (0.3 mM) failed to affect the 45Ca2+ e into striatal synaptosomes. Moreover, the aminoglycoside did not interfere with the ability of CRF to bind and activate its own receptor. ese results suggest that one of the mechanisms by which CRF stimulates synaptosomal TH activity may involve a receptor triggered phosphoinositides hydrolysis and the combined actions of Ca*+ and protein Kinase C.
495
Aguilera, G.. M.A. Millan, R.L. Hauger and K.J. Catt, 1987, Annals of the New York Academy of Sciences, 512.48. Olianas, M.C. and P. Onali. 1988, Eur. J. Phannacol. 150. 389. Olialfas, M.C. and P. Onali, 1989, Eur. J. Pharmacol. 166, 165.
Diamant, M. and de Wied, D. RudorfMagnu Institute, Medical Faculty, University of Utrecht. Vondellaan 6. 3521 GD Utrecht. The Netherkmdr Corticotropin-releasing factor (CRF), in addition to the regulation of pituitary ACTH secretion, elicits changes in autonomic nervous system (ANS) activity that are similar to those produced by a variety of stressful stimuli.
Accordingly, when administered into the lateral ventricle (icv), CRF has been shown to enhance novelty-induced behavioral activation in rats (Veldhuis and De Wied, 1984). elevate plasma concentrations of epinephrine. norepinephrine and glucose and raise heart rate and blood pressure (Brown and Fisher, 1985). Inasmuch as the above mentioned neuroendocrine-induced changes have been studied separately under widely different conditions, the underlying mechanism of action by which CRF may coordinate this generalized adaptive response to various types of stress, has not yet been elucidated. In order to examine the physiological role of brain CRF in mediating stress-induced autonomic and behavioral changes, we have simultaneously monitored changes in heart rate (HR), body temperature (BT) and behavioral responses after icv administration of CRF in rats in their home cages. HR and BT were measured by a computerized telemetry system (Mini-mitter Co., Sunriver, OR) consisting of an implantable transmitter, a receiver and a data acquisition system. Recording of behavior was performed by the I5th set sampling procedure, by which the observer determined grooming behavior and locomotion every 15th set during 50 min. Both behavioral recording and HR and BT measurements began IO min after icv administration of either CRF (300 ng or 1000 ng per rat) or artificial cerebrospinal fluid (ACSF control). Icv CRF raised both HR and BT significantly in a dose-dependent fashion during the 50 min registration period when compared to ACSF and basal (i.e. unstimulated) values. Both 300 ng and 1000 ng were shown to increase grooming behavior and locomotion in rats whereas ACSF did not affect any of these behavioral responses. It was concluded that icv administeraJ CRF induces changes in HR and BT and causes behavioral activation in rats in their home cages. The differential involvement of the sympathetic and the parasympathetic nervous system in the autonomic responses to icv CRF and the possible role of the accompanying CRF-induced behavioral activation in the autonomic changes will be discussed. Table 1 The effect of icv CRF on heart rate in rats in the home cage. Mean heart rate [BPMJf SEM
ACSF 3OOngCRF 1000 ng CRF
10-30 min
30-60 min
lo-60 min after icv injection
346f 6.2 373f15.7 * 417* 6.2 +
345i 5.7 380 f 8.2 * 407* 11.1 *
346& 5.5 378&11.5 * 410f 7.9 *
’ p -z 0.05 CRF vs. ACSF controls
ferences Brown, M.R. and L.A. Fisher, 1985, Fed. Proc. 44,243. Veldhuis, H.D. and De Wied, D., 1984. Pharmacol. B&hem. Behav. 21, 707.
in brain regions following the i.c.v. administration of saline or ET-1 ( * P < 0.05 values are
1.9Of0.06 2.13*0.07 1.79kO.02 1.82f0.08
2.16f0.08 2.46*0.04 2.34 + 0.04 2.16f0.01
* * * *
n conclusion, i.c.v. ET-I m fied 2-DG uptake in distinct brain regions. The dissociation of the effects of i.v. and stration of ET-I for direct rather than vascular effects of ET-1 on neuronal activity and support a i.c.v. aa ulator of neuronal function. roIe for
hxx.
_ (1989) P.N.NA.S. In press. CR et al. (1989) Newosci. Let. 97, 276-279. ff, L et al. (1977) J. Neurachem.28,8%-916.
Qlianas
MC.
and On&
P.
Department of Neurosciences, Universiv of Cagliari, via Porcell4, 09124 Cagliari, Italy Corticotropin-releasing factor
(CRF) is considered to function as a neurotransmitter/neuromodulator in different tbalamic pathways of the CNS (Aguilera et al., 1987) We have observed that this peptide is a potent f tyrosine hydroxylase (TII) activity of rat and mouse striatal synaptosomes (Olianas and Onali, 1988; activity was assayed in extracts prepared by centrifugation and sonication of mouse striatal synaptosomes ed with the peptide. In mouse striatum, CRF maximally increases the enzyme activity by 60 (p < 0.001). as a function of low concentrations of the pterin cofactor D,L-dmethyl-5,6,7,8-tetrato 0.4 mM), the stimulatory effect of CRF consisted in an increase of the app. V,,,, of the enzyme form with high affinity for the cofactor. The CRF response occurred at nanomolar concentrations of the ), was significantly antagonized by the CRF receptor antagonist a-helical CRF 9-41 (Ki 120 eked by sauvagine (EC 50 5 nM) and urotensin I (EC 50 10 nM), two peptides homologous to CRF. n of synaptosomal TH activity displayed a marked dependence on extracellular Ca*+ concentrain a Ca+-free medium and maximal at about 0.5 mM extracellular free Ca*+. Moreover, the CRF d by polymyxin B, a protein kinase C inhibitor. Neomycin, an aminoglycoside which binds to ysis of phoshoinositides, maximally reduced the CRF-stimulated TH activity by 60% with an IC ue of about 0.15 mM. Under similar experimental conditions, neomycin (0.3 mM) failed to affect the 45Ca2+ e into striatal synaptosomes. Moreover, the aminoglycoside did not interfere with the ability of CRF to bind and activate its own receptor. ese results suggest that one of the mechanisms by which CRF stimulates synaptosomal TH activity may involve a receptor triggered phosphoinositides hydrolysis and the combined actions of Ca*+ and protein Kinase C.
495
Aguilera, G.. M.A. Millan, R.L. Hauger and K.J. Catt, 1987, Annals of the New York Academy of Sciences, 512.48. Olianas, M.C. and P. Onali. 1988, Eur. J. Phannacol. 150. 389. Olialfas, M.C. and P. Onali, 1989, Eur. J. Pharmacol. 166, 165.
Diamant, M. and de Wied, D. RudorfMagnu Institute, Medical Faculty, University of Utrecht. Vondellaan 6. 3521 GD Utrecht. The Netherkmdr Corticotropin-releasing factor (CRF), in addition to the regulation of pituitary ACTH secretion, elicits changes in autonomic nervous system (ANS) activity that are similar to those produced by a variety of stressful stimuli.
Accordingly, when administered into the lateral ventricle (icv), CRF has been shown to enhance novelty-induced behavioral activation in rats (Veldhuis and De Wied, 1984). elevate plasma concentrations of epinephrine. norepinephrine and glucose and raise heart rate and blood pressure (Brown and Fisher, 1985). Inasmuch as the above mentioned neuroendocrine-induced changes have been studied separately under widely different conditions, the underlying mechanism of action by which CRF may coordinate this generalized adaptive response to various types of stress, has not yet been elucidated. In order to examine the physiological role of brain CRF in mediating stress-induced autonomic and behavioral changes, we have simultaneously monitored changes in heart rate (HR), body temperature (BT) and behavioral responses after icv administration of CRF in rats in their home cages. HR and BT were measured by a computerized telemetry system (Mini-mitter Co., Sunriver, OR) consisting of an implantable transmitter, a receiver and a data acquisition system. Recording of behavior was performed by the I5th set sampling procedure, by which the observer determined grooming behavior and locomotion every 15th set during 50 min. Both behavioral recording and HR and BT measurements began IO min after icv administration of either CRF (300 ng or 1000 ng per rat) or artificial cerebrospinal fluid (ACSF control). Icv CRF raised both HR and BT significantly in a dose-dependent fashion during the 50 min registration period when compared to ACSF and basal (i.e. unstimulated) values. Both 300 ng and 1000 ng were shown to increase grooming behavior and locomotion in rats whereas ACSF did not affect any of these behavioral responses. It was concluded that icv administeraJ CRF induces changes in HR and BT and causes behavioral activation in rats in their home cages. The differential involvement of the sympathetic and the parasympathetic nervous system in the autonomic responses to icv CRF and the possible role of the accompanying CRF-induced behavioral activation in the autonomic changes will be discussed. Table 1 The effect of icv CRF on heart rate in rats in the home cage. Mean heart rate [BPMJf SEM
ACSF 3OOngCRF 1000 ng CRF
10-30 min
30-60 min
lo-60 min after icv injection
346f 6.2 373f15.7 * 417* 6.2 +
345i 5.7 380 f 8.2 * 407* 11.1 *
346& 5.5 378&11.5 * 410f 7.9 *
’ p -z 0.05 CRF vs. ACSF controls
ferences Brown, M.R. and L.A. Fisher, 1985, Fed. Proc. 44,243. Veldhuis, H.D. and De Wied, D., 1984. Pharmacol. B&hem. Behav. 21, 707.