Somatostatin receptors in the ventral pallidum/substantia innominata modulate rat locomotor activity.
BACKGROUND
Somatostatin and its receptors (sst(1) and sst(2)) have been localized in brain nuclei implicated in motor control, such as the nucleus accumbens, ventral pallidum (VP) and substantia innominata (SI).


OBJECTIVE
The objective of the study is to investigate the effect of somatostatin and selective sst(1) and sst(2) analogs infused in the VP/SI on the locomotor activity of the rat.


METHODS
Somatostatin (15, 30, 60, 120 and 240 ng/0.5 microl/side), CH275 (sst(1) analog; 60, 180, 240 and 480 ng/0.5 microl/side), MK678 (sst(2) analog; 120, 240 and 480 ng/0.5 microl/side), L-809,087 (sst(4) agonist, 240 ng/0.5 microl/side) or saline (vehicle) were infused bilaterally in the VP/SI of the rat and locomotor activity measured for 60 min. The effect of SRA-880 (sst(1) antagonist) and CYN-154806 (sst(2) antagonist) on somatostatin-, CH275- and MK678-mediated locomotor activity was also ascertained.


RESULTS
Somatostatin decreased locomotor activity in the first 30 min after its infusion in the VP/SI and in a dose-dependent manner. The sst(1) and sst(2) antagonists, SRA-880 and CYN-154806, respectively, reversed the somatostatin effect. The sst(1) and sst(2) agonists CH275 and MK678, respectively, mimicked somatostatin's actions, while the selective sst(4) agonist L-809,087 had no effect. Moreover, SRA-880 and CYN-154806 reversed the respective agonist action on locomotor activity.


CONCLUSIONS
The present study provides functional evidence for the presence of sst(1) and sst(2) receptors in the VP/SI and their implication in motor control. The mechanism via which somatostatin and agonists mediate the attenuation of locomotor activity is presently being investigated.
Marazioti
A
A
Laboratory of Pharmacology, Faculty of Medicine, University of Crete, Heraklion, Greece.
Kastellakis
A
A
Antoniou
K
K
Papasava
D
D
Thermos
K
K
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005917:Globus Pallidus / Q000187:drug effects / Q000502:physiology* / Q000601:surgery; D007276:Injections, Intraventricular; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology*; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017481:Receptors, Somatostatin / Q000037:antagonists & inhibitors / Q000502:physiology*; D013004:Somatostatin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D013238:Stereotaxic Techniques; D013377:Substantia Innominata / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
C488795:1,2,3,4,4a,5,10,10a-octahydro-6-methoxy-1-methylbenz(g)quinoline-3-carboxylic acid 4-(4-nitrophenyl)piperazine amide; C110576:CH 275; C403089:CYN 154806; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010879:Piperazines; D011804:Quinolines; D017481:Receptors, Somatostatin; D013004:Somatostatin; C040968:seglitide