No changes in densities of cannabinoid receptors in the superior temporal gyrus in schizophrenia

Objective In recent years,abnormal changes in the endocannabinoid system have been found in schizophrenia. The superior temporal gyrus（STG）is strongly implicated in the pathophysiology of schizophrenia,particularly with regards to auditory hallucinations.In this study,we investigated the binding density of cannabinoid CB1 receptors in the STG of schizophrenia patients compared to control subjects.Methods Quantitative autoradiography was used to investigate the binding densities of[^3H]SR141716A（a selective antagonist）and[^3H]CP-55940（an agonist）to the CB1 receptors in the STG.Post-mortem brain tissue was obtained from the NSW Tissue Resource Centre（Australia）.Results Contrasting to previous findings in the alterations of CB1 receptor densities in the prefrontal,anterior and posterior cingulate cortex of schizophrenia,which were suggested to be associated to impairment of cognition function,no significant difference was found between the schizophrenia and control cases in both[^3H]SR141716A and[^3H]CP-55940 binding. Conclusion We suggest that CB1 receptors in the STG are not involved in the pathology of schizophrenia and the auditory hallucination symptom of this disease.

Prepulse Inhibition of Auditory Cortical Responses in the Caudolateral Superior Temporal Gyrus in Macaca mulatta

Prepulse inhibition(PPI) refers to a decreased response to a startling stimulus when another weaker stimulus precedes it. Most PPI studies have focused on the physiological startle reflex and fewer have reported the PPI of cortical responses. We recorded local field potentials(LFPs) in four monkeys and investigated whether the PPI of auditory cortical responses(alpha, beta, and gamma oscillations and evoked potentials) can be demonstrated in the caudolateral belt of the superior temporal gyrus(STGcb). We also investigated whether the presence of a conspecific, which draws attention away from the auditory stimuli, affects the PPI of auditory cortical responses. The PPI paradigm consisted of Pulse-only and Prepulse + Pulse trials that were presented randomly while the monkey was alone(ALONE) and while another monkey was present in the same room(ACCOMP). The LFPs to the Pulse were significantly suppressed by the Prepulse thus, demonstrating PPI of cortical responses in the STGcb. The PPI-related inhibition of the N1 amplitude of the evoked responses and cortical oscillations to the Pulse were not affected by the presence of a conspecific. In contrast, gamma oscillations and the amplitude of the N1 response to Pulse-only were suppressed in the ACCOMP condition compared to the ALONE condition. Thesefindings demonstrate PPI in the monkey STGcb and suggest that the PPI of auditory cortical responses in the monkey STGcb is a pre-attentive inhibitory process that is independent of attentional modulation.