Effects of acute systemic and intra-cerebral stimulation of cannabinoid receptors on sensorimotor gating, locomotion and spatial memory in rats.
BACKGROUND
Cannabinoid CB(1) receptors in the brain are targets of both endocannabinoid signalling and the psychoactive compounds of the hemp plant. They mediate neuronal effects of their ligands in various corticolimbic and striatal circuits by presynaptic regulation of transmitter release.


OBJECTIVE
This study investigates acute systemic effects of the full CB(1) receptor agonist WIN 55,212-2 (WIN) on prepulse inhibition (PPI) of the acoustic startle response (ASR), locomotor activity and spatial memory retrieval in an eight-arm radial-maze task. Furthermore, we tested the effect of local intra-cerebral micro-infusions of WIN into the nucleus accumbens (NAc), ventral tegmental area (VTA), dorsal (dHIP) and ventral (vHIP) hippocampus and medial prefrontal cortex (mPFC).


RESULTS
Systemic WIN (1.2 mg/kg) reduced PPI without affecting ASR, had no effect on locomotion in the open field, but impaired retrieval of spatial memory. Infusions of 5 microg/0.3 microl WIN into either NAc (core or shell), dHIP or VTA did not affect PPI and locomotion immediately afterwards. However, PPI was significantly reduced after intra-mPFC and intra-vHIP infusion of WIN. Furthermore, WIN infusion into dHIP increased the number of reference memory errors in the maze, suggesting impairment of memory retrieval.


CONCLUSIONS
Our data support the notion that CB(1) receptor stimulation impairs sensorimotor gating most likely by modulation of neurotransmitter release in mPFC and vHIP. The lack of effects of local WIN infusions in NAc and VTA might be due to low receptor abundance in these regions. Additionally, CB(1) receptor activation in dHIP impairs spatial memory retrieval. Taken together, cortico-hippocampal cannabinoid receptors play an essential role in the regulation of cognitive and behavioural processes.
Wegener
Nico
N
Brain Research Institute, Department of Neuropharmacology, University of Bremen, P.O. Box 330440, 28334 Bremen, Germany. nwegener@uni-bremen.de
Kuhnert
Sybille
S
Thüns
Annika
A
Roese
Rasmus
R
Koch
Michael
M
D000818:Animals; D048588:Benzoxazines / Q000008:administration & dosage / Q000494:pharmacology*; D001921:Brain / Q000502:physiology*; D063386:Cannabinoid Receptor Agonists; D004558:Electric Stimulation; D006624:Hippocampus / Q000502:physiology; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008568:Memory / Q000187:drug effects*; D008845:Microinjections; D009025:Morpholines / Q000008:administration & dosage / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D009281:Naphthalenes / Q000008:administration & dosage / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D009714:Nucleus Accumbens / Q000502:physiology; D017397:Prefrontal Cortex / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013216:Reflex, Startle / Q000187:drug effects*; D013028:Space Perception / Q000187:drug effects*
D048588:Benzoxazines; D063386:Cannabinoid Receptor Agonists; D009025:Morpholines; D009281:Naphthalenes; D018377:Neurotransmitter Agents; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone