Effects of CCK-4 infusion on the acoustic eye-blink startle and psychophysiological measures in healthy volunteers

Variants Near CCK Receptors are Associated With Electrophysiological Responses to Pre-pulse Startle Stimuli in a Mexican American Cohort

Neurophysiological measurements of the response to pre-pulse and startle stimuli have been suggested to represent an important endophenotype for both substance dependence and other select psychiatric disorders. We have previously shown, in young adult Mexican Americans (MA), that presentation of a short delay acoustic pre-pulse, prior to the startle stimuli can elicit a late negative component at about 400 msec (N4S), in the event-related potential (ERP), recorded from frontal cortical areas. In the present study, we investigated whether genetic factors associated with this endophenotype could be identified. The study included 420 (age 18-30 years) MA men (n = 170), and women (n = 250). DNA was genotyped using an Affymetrix Axiom Exome1A chip. An association analysis revealed that the CCKAR and CCKBR (cholecystokinin A and B receptor) genes each had a nearby variant that showed suggestive significance with the amplitude of the N4S component to pre-pulse stimuli. The neurotransmitter cholecystokinin (CCK), along with its receptors, CCKAR and CCKBR, have been previously associated with psychiatric disorders, suggesting that variants near these genes may play a role in the pre-pulse/startle response in this cohort.

Induced fear reduces the effectiveness of a placebo intervention on pain

Fear was induced by the anticipation of electric shock in order to investigate whether fear reduced the effectiveness of a placebo intervention on reported pain and the acoustic startle reflex. Thirty-three subjects participated in a 3 Condition (Natural History [NH], Placebo [P], Placebo+Fear [PF])×3 Test (Pretest, Posttest 1, Posttest 2) within-subject design, tested on 3 separate days. Measures of fear were fear of pain (FOP), measured by the Fear of Pain Questionnaire (FPQ-III); fear-potentiated startle; and a self-report measure that assessed the effectiveness of the fear induction procedure. In the pain intensity data, there was a trend towards a placebo effect. This trend was abolished by induced fear, and was most pronounced in subjects who were highest in measures of fear. The placebo manipulation also caused a reduction in startle reflex amplitude. This effect was abolished by induced fear, and was strongest amongst high FOP subjects. In conclusion, induced fear abolished placebo analgesia, and this effect was strongest in subjects who had high scores on measures of fear.

The relation of emotions to placebo responses

The hypothesis put forth is that expectations of treatment effects reduce negative emotions and thereby reduce symptoms, e.g. pain. Negative emotions increase pain, and it is hypothesized that placebos reduce pain by reducing negative emotions, i.e. feelings of nervousness, fear and anxiety. Placebo analgesia has been shown to be mediated via opioid activity, and relaxation increases opioid activity. The placebo acquires its relaxing effect due to verbal information that pain will be reduced, or due to associations between the placebo and the reduction in pain after effective treatment. Thus, the placebo signals that unpleasantness will be less after administration of the placebo. This involves negative reinforcement which is due to activation of a dopaminergic system that has been found to be activated during placebo analgesia and is involved in positive emotions. The nocebo effect of increased pain is, consistent with this model, because of increased fear and anxiety. The new aspect of the presented model is the hypothesis that expectations reduce negative emotions, and that negative reinforcement that involves the dopaminergic reinforcement system should be a contributor to placebo responses.

Is fear of pain related to placebo analgesia?

OBJECTIVE

Verbal information that a painkiller has been administered generates an expectation of pain relief which in turn decreases pain. This expectation-based pain reduction is termed placebo analgesia. We hypothesized that fear of pain would be related to higher stress and pain intensity and to reduced placebo analgesia.

METHODS

Sixty-three students (30 females) participated in a Two-Condition (placebo, natural history)xFive-Test (one pretest, four post-tests) within-subjects design. Heat pain was induced by a 30x30-mm contact thermode to the medial volar forearm. Each pain test lasted for 4 min at a temperature of 46 degrees C. Stress, arousal, and pain intensity and pain unpleasantness were rated on 100-mm visual analogue scales.

RESULTS

Fear of pain was related to higher anticipatory stress and to higher stress and pain intensity during pain. Fear of pain was also related to reduced placebo analgesic responding.

CONCLUSION

Fear of pain was positively related to stress both during pain and in the anticipation of pain, and negatively related to placebo analgesia. Previous research has indicated a role for increased stress in the nocebo response, and the present findings suggest that decreased stress may strengthen the placebo response.

Protective and therapeutic effects of glyprolines in psychoemotional stress induced by cholecystokinin-4 injection

Experiments on outbred albino male rats showed that psychoemotional stress induced by intraperitoneal injection of cholecystokinin-4 (100 microg/kg) increased anxiety, impaired orientation and exploration activities in the elevated plus-maze and hole-board tests, and increased the level of depression of Porsolt test. Preliminary intranasal administration of glyprolines (15 min before cholecystokinin) in a dose of 3.7 micromol/kg prevented the development of stress-induced behavioral disturbances. Administration of peptides 30 min after cholecystokinin-4, i.e., to rats with developed behavioral disturbances, almost completely abolished these disturbances.

Effects of background noise on the human startle reflex and prepulse inhibition

Three experiments investigated whether background noise modified the startle blink reflex and prepulse inhibition (PPI). In Experiment 1 background noise was about 28 (ambient), 40, and 60 dB; in Experiments 2 and 3 background noise was ambient and 60 dB. Prepulses were 70-dB tones (Experiments 1 and 3) or a tactile stimulus (Experiment 2). Startle-eliciting stimuli were 94-dB noise (Experiments 1 and 2) or an airpuff to the face (Experiment 3). Prepulses were presented at stimulus onset asynchronies of 30, 60, 120, 240, and 2000 ms relative to the startle-eliciting stimulus. Background noise of 60 dB had no effect on control reflexes, whereas 40-dB background noise increased control reflexes. Background noise decreased PPI, but only when an acoustic stimulus was used as prepulse. In sum, the findings show that background noise reduces the signal-to-noise ratio of acoustic prepulses and decreases their modulatory effect on the startle reflex.

Psychopharmacological possibilities in the acute disaster setting

This article focuses on possible psychopharmacological interventions in the immediate post disaster setting. As there is little evidence for the efficacy or effectiveness of such interventions-given the difficulty in performing randomized, double-blind, placebo controlled studies with these populations-the article will delineate the neurobiological basis for pathological sequelae and theoretical drug interventions targeting putative disease mechanisms.

A review of the modulation of the startle reflex by affective states and its application in psychiatry

OBJECTIVE

To provide an overview of startle reflex methodologies applied to the examination of emotional and motivational states in humans and to review the findings in different forms of psychopathology.

METHODS

Pertinent articles were searched mostly via MEDLINE and PsycINFO.

RESULTS

The startle reflex is a non-invasive translational tool of research that bridges the gap between animal and human investigations. Startle is used to study fear and anxiety, affective disturbances, sensitization, motivational states, and homeostasis.

CONCLUSIONS

The startle reflex is highly sensitive to various factors that are of interest in the studies of emotional disorders and has promoted new areas of investigations in psychiatry. However, research in psychiatry is still in its infancy and most findings await replication. Future progress will benefit from the development of innovative and powerful designs tailored to investigate specific disorders.

SIGNIFICANCE

The startle reflex has utility as a research tool to examine trauma-related disorders, fear learning, drug addiction, and to contrast affective states and emotional processing across diagnostic groups, but its usefulness as a diagnostic tool is limited.

Differential startle reactivity following central CCK-8S and systemic Boc CCK-4 administration in mice: antecedent stressor history and testing condition

The influence of intraventricular cholecystokinin-8S (CCK-8S) and systemic N-t-Boc-Trp-Met-Asp-Phe-amide (Boc CCK-4) was evaluated in the acoustic and fear-potentiated startle paradigms in CD-1 mice. In the light + tone startle condition. CCK-8S increased startle 168 hr after administration, compared with saline. In the tone startle condition, CCK-8S decreased startle immediately and 24 hr after administration, compared with saline. Among nonshocked mice, CCK-8S increased startle at 48 and 168 hr, compared with saline. In the light + tone condition, 5 microg Boc-CCK-4 did not influence startle, whereas 15 microg Boc CCK-4 decreased startle immediately, 24 hr, and 48 hr following administration. Results demonstrate that antecedent environmental experiences interact with subsequent pharmacological challenges in provoking the temporal expression of alterations in startle magnitude.

Effects of acute cholecystokinin infusion on hemispheric EEG asymmetry and coherence in healthy volunteers

This study investigated the effects of continuous slow infusion of cholecystokinin tetrapeptide (CCK-4), a neuropeptide with panicogenic properties, on functional hemispheric differences, as indexed by quantitative electroencephalographic (EEG) asymmetry and coherence measures. Twenty-four adult volunteers (15 females and 9 males) were assigned to infusion with either placebo or CCK-4 in a randomized, double-blind, parallel-group design, with EEG being recorded before and during (10 and 40 min) a 60-min infusion period. No significant treatment differences were observed for absolute EEG power but, compared to placebo, CCK-4 infusion increased asymmetry and reduced coherence of slow-wave activity at midtemporal recording sites. These findings support the contention that functional imbalance of the temporal cortex, perhaps mediated by CCK-4, is involved in panic disorder (PD).

Human models as tools in the development of psychotropic drugs

Despite the growing means devoted to research and development (R α D) and refinements in the preclinical stages, the efficiency of central nervous system (CMS) drug development is disappointing. Many drugs reach patient studies with an erroneous therapeutic indication andlor in incorrect doses. Apart from the first clinical studies, which are conducted in healthy volunteers and focus only on safety, iolerability, and pharmacokinetics, drug development mostly relies on patient studies. Psychiatric disorders are characterized by heterogeneity and a high rate of comorbidity. It is becoming increasingly difficult to recruit patients for clinical trials and there are many confounding factors in this population, for example, those related to treatments. In order to keep patient exposure and financial expenditure to a minimum, it is important to avoid ill-designed and inconclusive studies. This risk could be minimized by gathering pharmacodynamic data earlier in development and considering that the goal of a phase 1 plan is to reach patient studies with clear ideas about the compound's pharmacodynamic profile, its efficacy in the putative indication (proof of concept), and pharmacokinetic/pharmacodynamic relationships, in addition to safety, tolerability, and pharmacokinetics. Human models in healthy volunteers may be useful tools for this purpose, but their use necessitates a global adaptation of the phase scheme, favoring pharmacodynamic assessments without neglecting safety. We are engaged in an R α D program aimed to adapt existing models and develop new paradigms suitable for early proof of concept substantiation.

Blink rate variability in patients with panic disorder: new trial using audiovisual stimulation

Several lines of evidence have implicated central dopaminergic pathways in the modulation of spontaneous blink rate (BR). Furthermore, previous studies have indicated a relationship between spontaneous BR and anxiety and/or depression. However, to our knowledge, there is no report on the examination of BR in a group of patients with panic disorder (PD). During the conditions of rest and with audiovisual stimulation, exposed to a video of imaginary experiences, such as driving a motor vehicle or diving into the sea, BR was examined in 11 male patients with PD and compared with the BR of 16 age-matched normal controls. The BR was significantly higher in PD patients relative to normal controls under both conditions. In particular, the PD group had a higher BR score during the sea scene as relaxation compared with the normal controls. In conclusion, although the sample size was small the present preliminary study, these findings suggest that BR may have potential for application in the assessment of anxiety state, which is consistent with previous studies.

Acute cholecystokinin effects on event-related potentials in healthy volunteers

This study investigated the effects of a continuous slow infusion of cholecystokinin tetrapeptide (CCK-4), a neuropeptide with panicogenic properties, on brain event-related potentials (ERPs) in healthy adults. Twenty-four volunteers, 15 females and 9 males, were assigned to infusion with either placebo or CCK-4 in a randomized, double-blind, parallel group design. ERPs, elicited within a standard auditory odd-ball paradigm requiring the counting of rare (20%) occurring 'deviant' tones interspersed among more frequent (80%) occurring 'standard' tones, were assessed once before infusion, and at 10 min and 40 min after the onset of infusion. Compared with the placebo, CCK-4 delayed the latencies of N100 and P200 components elicited by 'deviant' stimuli. No significant treatment differences were observed with respect to N200, P300b, mood or adverse symptoms. These preliminary findings suggest that CCK-4 may interfere with information processing relating to the selection of significant stimuli and as such, may be of relevance to mechanisms underlying panic disorder.

A double-blind, placebo-controlled study on the effects of Gotu Kola (Centella asiatica) on acoustic startle response in healthy subjects

Investigations of the pharmacologic profile of medicinal plants have revealed that a number of plants with purported anxiolytic activity bind to cholecystokinin (CCK) receptors. This finding is intriguing in view of the proposed involvement of CCK in the pathophysiology of fear and anxiety. This double-blind, placebo-controlled study was undertaken to evaluate the anxiolytic activity of Gotu Kola (Centella asiatica) in healthy subjects. Gotu Kola has been used for centuries in Ayurvedic and traditional Chinese medicine to alleviate symptoms of depression and anxiety. Recent studies in the rat have shown that long-term pretreatment with Gotu Kola decreases locomotor activity, enhances elevated-plus maze performance, and attenuates the acoustic startle response (ASR). In this study, the authors evaluated the effects of Gotu Kola on the ASR in humans. Subjects were randomly assigned to receive either a single 12-g orally administered dose of Gotu Kola (N = 20) or placebo (N = 20). The results revealed that compared with placebo, Gotu Kola significantly attenuated the peak ASR amplitude 30 and 60 minutes after treatment. Gotu Kola had no significant effect on self-rated mood, heart rate, or blood pressure. These preliminary findings suggest that Gotu Kola has anxiolytic activity in humans as revealed by the ASR. It remains to be seen whether this herb has therapeutic efficacy in the treatment of anxiety syndromes.