THURSDAY, Oct. 27 (HealthDay News) -- Disrupted temporal coordination of hippocampal and medial prefrontal cortical networks (mPFC) due to systemic activation of the cannabinoid receptor is associated with impaired accuracy during working-memory task performance in rats, according to an experimental study published in the Oct. 26 issue of the Journal of Neuroscience.
Michal T. Kucewicz, from the University of Bristol in the United Kingdom, and colleagues investigated the role of CP55940, a potent agonist of brain cannabinoid receptors, in network oscillations during hippocampal and mPFC interactions in rats. Electrical activity from neurons was measured in rats which were given systemic injections of CP55940.
The investigators found that, during quiet wakefulness and rest, local field potential power in CA1 of the hippocampus and power in mPFC were reduced in a dose-dependent manner by 0.1 to 30 Hz and 30 to 100 Hz, respectively, following administration of CP55940. CP55940 induced deficits in the hippocampal theta and prefrontal gamma oscillations during decision-making phases of a spatial working-memory task, and disrupted theta-frequency coherence was noted between the two structures. The changes in coordinated limbic-cortical network activities were associated with decreased accuracy during task performance, disrupted phase-locking of prefrontal single-unit spiking to the local hippocampal theta and gamma rhythms, and reduced task-dependent activity in certain mPFC units.
"We show that impairments in a spatial working-memory task caused by systemic activation of cannabinoid receptors in rats were accompanied by disrupted temporal coordination of neuronal activity both within and across hippocampal and prefrontal cortical networks," the authors write.