Effects of RG1068 (Secretin) on Information Processing in Schizophrenia

In a recent placebo-controlled, double-blind, multicenter study of Secretin in refractory schizophrenics, we found that a patient who received Secretin (1.0 g/kg) intravenously, showed a marked improvement in eye blink conditioning following infusion. This subject also showed a clinical improvement of \> 20% on the Total Score and Total Negative Score of the Positive and Negative Syndrome Scale (PANSS). Therefore, the primary objective of this study is to confirm and extend this observation in a larger group of individuals with schizophrenia. In this 24 to 48 hour experiment, the acquisition and extinction of the conditioned blink response will be assessed in participants with schizophrenia who are randomly assigned to one of two double blind treatment groups: (1) subcutaneous saline or (2) subcutaneous Secretin (20 ug/kg). Enrolled participants will remain on their stable medication regime (i.e., psychotropic medications and related treatments will not be manipulated). Furthermore, given evidence that Secretin administration increases the amygdala's activation during experimental presentation of fear-related facial cue stimuli, we wish to also investigate the effects of the experimental agent on psychophysiological processes putatively related to amygdala function. Prepulse inhibition is a widely studied paradigm in the schizophrenia literature, thought to reflect disruption of early sensory-motor gating that is present in both individuals with schizophrenia and their unaffected biological relatives, and can be mediated by various limbic structures including the amygdala. Therefore, as a secondary aim, the effects of Secretin will be tested on affect modulation, pre-pulse inhibition, and pre-pulse facilitation of the acoustic startle response using common psychophysiological research procedures. These procedures are frequently used in our laboratory and are currently approved for our use by the IRBs at both IUPUI and IUB.