TY - JOUR
T1 - Release of somatostatin-like immunoreactivity from enriched enteric nerve varicosities of rat ileum
AU - Kurjak, Manfred
AU - Schusdziarra, Volker
AU - Allescher, Hans Dieter
N1 - Funding Information:
The authors acknowledge the co-operation of Prof. Dr. Bliimel and his collaborators, Dept. Exp. Surgery, Technical University of Munich. We would like to thank S. Maguire for her expert technical assistance. The study was supported by Deutsche Forschungsge-meinschaft A1 245/2-1 and AI 245/2-2.
PY - 1995/8/15
Y1 - 1995/8/15
N2 - Synaptosomes were isolated from rat ileum by various steps of differential centrifugation. The peptide content for somatostatin-like immunoreactivity was used as marker for neuronal membranes. The enriched synaptosomal fraction (P2) showed a good enrichment of somatostatin content (4-fold) in comparison to the post-nuclear supernatant. The basal release of somatostatin-like immunoreactivity was 26 ± 3 pg/mg tissue protein. KCl-evoked depolarization (65 mM) caused a significant increase of somatostatin-like immunoreactivity release (72 ± 11 pg/mg, n = 12, P < 0.001) compared to basal release. In Ca2+-free medium the evoked release of somatostatin-like immunoreactivity was abolished. A substantial increase of somatostatin-like immunoreactivity release (52 ± 7 pg/mg, n = 12, P < 0.05) was also observed in the presence of the Ca2+ ionophore A-23187. The cholinergic agonist carbachol elicited a dose-dependent release of somatostatin-like immunoreactivity (10-7 M: 54 ± 8 pg/mg, 10-6 M: 63 ± 6 pg/mg, 10-5 M: 53 ± 5 pg/mg, n = 12, P < 0.001), which was blocked by atropine (10-6 M: 35 ± 6 pg/mg, n = 12, P < 0.001), but not by hexamethonium. Other presynaptic modulating substances such as serotonin, the selective neurokinin-B agonist [βAsp4,MePhe7]neurokinin B-(4-10), neurotensin, cholecystokinin-8, caerulein and pentagastrin had no stimulatory effect on release of somatostatin-like immunoreactivity. In summary, somatostatin-like immunoreactivity can be released from enteric synaptosomes by both depolarization with KCl and cholinergic stimulation via a muscarinic mechanism. The synaptosomes of intrinsic nerves offer an approach to study release of neuronal somatostatin on the subcellular level.
AB - Synaptosomes were isolated from rat ileum by various steps of differential centrifugation. The peptide content for somatostatin-like immunoreactivity was used as marker for neuronal membranes. The enriched synaptosomal fraction (P2) showed a good enrichment of somatostatin content (4-fold) in comparison to the post-nuclear supernatant. The basal release of somatostatin-like immunoreactivity was 26 ± 3 pg/mg tissue protein. KCl-evoked depolarization (65 mM) caused a significant increase of somatostatin-like immunoreactivity release (72 ± 11 pg/mg, n = 12, P < 0.001) compared to basal release. In Ca2+-free medium the evoked release of somatostatin-like immunoreactivity was abolished. A substantial increase of somatostatin-like immunoreactivity release (52 ± 7 pg/mg, n = 12, P < 0.05) was also observed in the presence of the Ca2+ ionophore A-23187. The cholinergic agonist carbachol elicited a dose-dependent release of somatostatin-like immunoreactivity (10-7 M: 54 ± 8 pg/mg, 10-6 M: 63 ± 6 pg/mg, 10-5 M: 53 ± 5 pg/mg, n = 12, P < 0.001), which was blocked by atropine (10-6 M: 35 ± 6 pg/mg, n = 12, P < 0.001), but not by hexamethonium. Other presynaptic modulating substances such as serotonin, the selective neurokinin-B agonist [βAsp4,MePhe7]neurokinin B-(4-10), neurotensin, cholecystokinin-8, caerulein and pentagastrin had no stimulatory effect on release of somatostatin-like immunoreactivity. In summary, somatostatin-like immunoreactivity can be released from enteric synaptosomes by both depolarization with KCl and cholinergic stimulation via a muscarinic mechanism. The synaptosomes of intrinsic nerves offer an approach to study release of neuronal somatostatin on the subcellular level.
KW - Acetylcholine
KW - Ileum, rat
KW - Presynaptic mechanism
KW - Somatostatin
KW - Synaptosome
UR - http://www.scopus.com/inward/record.url?scp=0029120751&partnerID=8YFLogxK
U2 - 10.1016/0014-2999(95)00261-I
DO - 10.1016/0014-2999(95)00261-I
M3 - Article
C2 - 8521913
AN - SCOPUS:0029120751
SN - 0014-2999
VL - 281
SP - 295
EP - 301
JO - European Journal of Pharmacology
JF - European Journal of Pharmacology
IS - 3
ER -