Dose Response of Arginine Vasopressin to the CCK-B Agonist Pentagastrin James L. Abelson, M.D., Ph.D., Jean-Michel Le Mellédo, M.D., and Daniel G. Bichet, M.D., FRCPC Cholecystokinin (CCK) is a peptide neurotransmitter that agonist. However, this may have been due to a greater modulates hypothalamic-pituitary-adrenal (HPA) axis percentage of subjects releasing AVP in the higher dose activity and may be involved in fear or anxiety states. groups, rather than a direct effect of dose on magnitude of Arginine vasopressin (AVP) also modulates HPA axis response. AVP and ACTH responses were correlated, but activity and may play a role in fear conditioning. Few AVP response alone could not account for the magnitude of human studies have examined interactions between CCK the ACTH response. AVP release was significantly and AVP systems. To explore relationships between CCK-B correlated with anxiety symptom responses. These findings receptor activation, the HPA axis response, and AVP suggest a possible role for the CCK-B receptor in AVP release, a dose-response study using the CCK-B receptor release, which may be at least partially separate from its role agonist pentagastrin was conducted. Adrenocorticotropin in modulation of the HPA axis. Further work is needed to (ACTH) and cortisol results have been previously reported determine whether these are physiologically meaningful and AVP data is presented here. Thirty-five healthy interactions and to determine their functional implications. subjects were randomly assigned to receive placebo, or 0.2, [Neuropsychopharmacology 24:161–169, 2001] 0.4, 0.6, or 0.8 ␮g/kg doses of pentagastrin. AVP release © 2000 American College of Neuropsychopharmacology. appeared to increase with increasing doses of the CCK-B Published by Elsevier Science Inc. KEY WORDS: Cholecystokinin; Vasopressin; Pentagastrin; functioning as a neuromodulator of the hypothalamic- Anxiety; Panic disorder pituitary-adrenal (HPA) axis (Abelson and Liberzon 1999). CCK-B agonists, such as pentagastrin, activate the Cholecystokinin (CCK) is a peptide neurotransmitter that HPA axis in humans, stimulating release of adrenocorti- is widely distributed in brain areas involved with cogni- cotropin (ACTH) and cortisol (Abelson and Liberzon tive or emotional aspects of behavior, such as prefrontal 1999; Abelson et al. 1994; de Montigny 1989; Degli Uberti cortex, cingulate, hippocampus, amygdala, and the locus et al. 1983; Späth-Schwalbe et al. 1988). coeruleus (Lindefors et al. 1993; Saito et al. 1980). Some Levels of CCK and corticotropin-releasing hormone evidence suggests it may modulate stress responsiveness, (CRH) were found to be correlated in human cere- brospinal fluid, suggesting that central regulation of these two neuropeptides may be linked in humans; and From the University of Michigan Department of Psychiatry, Anx- this linkage may be tighter under conditions of stress iety Disorders Program, Ann Arbor, MI (JLA); Department of Psy- (Geracioti et al. 1999). Animal work also demonstrates chiatry, University of Alberta, Edmonton, Alberta, Canada (J- substantial interaction between CCK and the HPA axis. MLM); and University of Montreal, Hôpital Sacré-Coeur, Montreal, Quebec, Canada (DGB). The axis is directly sensitive to CCK activation (Kami- Address correspondence to: James L. Abelson, M.D., Ph.D., Rm laris et al. 1992; Matsumura et al. 1983; Mezey et al. C435, Med Inn Bldg/0840, 1500 E. Medical Center Drive, Ann 1986; Reisine and Jensen 1986); and CCK peptide is co- Arbor, MI 48109–0840. Received 24 January 2000; revised 4 May 2000; accepted 19 July localized with other HPA axis secretagogues (Kiss et al. 2000. 1984; Larsson and Rehfeld 1981; Mezey et al. 1986; Mill- NEUROPSYCHOPHARMACOLOGY 2001–VOL. 24, NO. 2 © 2000 American College of Neuropsychopharmacology Published by Elsevier Science Inc. 0893-133X/01/$–see front matter 655 Avenue of the Americas, New York, NY 10010 PII S0893-133X(00)00182-2 162 J.L. Abelson et al. NEUROPSYCHOPHARMACOLOGY 2001–VOL. 24, NO. 2 ington et al. 1992; Rehfeld 1978; Rehfeld and Larsson links, and potential relevance to mood and anxiety dis- 1981; Rehfeld et al. 1987; Vanderhaeghen et al. 1985). orders, further exploration of interactions between Central CCK systems are stress and glucocorticoid sen- CCK, AVP, and the HPA axis are warranted. We have sitive (Mezey et al. 1986; Siegel et al. 1987); and periph- recently demonstrated in human subjects that the CCK- eral CCK can regulate activity in central components of B agonist pentagastrin releases ACTH and cortisol in a the HPA axis (Chen et al. 1993). dose-dependent fashion (Abelson and Liberzon 1999). Though CCK-HPA axis interactions are well estab- We have also shown that another CCK-B agonist (CCK- lished, the mechanisms by which they interact remain 4) can release AVP in humans (Le Mellédo et al. in uncertain. Central regulation of the HPA axis is exerted press). To determine whether pentagastrin stimulates primarily through corticotropin-releasing hormone AVP release in a dose-dependent fashion and whether (CRH), arginine vasopressin (AVP), and negative gluco- AVP participates in the ACTH response to pentagas- corticoid inhibition (Aguilera 1994). Animal work sug- trin, we have now also examined plasma AVP re- gests that both CRH (Biró et al. 1993; Kamilaris et al. 1992) sponses following varying doses of intravenous penta- and AVP (Bondy et al. 1989; DeBold et al. 1984; Mezey et gastrin. al. 1986; Verbalis et al. 1987) could mediate CCK effects on the HPA axis. However, due to substantial cross spe- cies variation in CCK function (Hinks et al. 1995; Wood- METHODS ruff et al. 1991), human studies will be needed to clarify Subjects these mechanisms in humans. CCK-induced release of ACTH differs from that seen with human CRH in its ra- As previously described (Abelson and Liberzon 1999), pidity, brevity, and relative resistance to cortisol feedback subjects were 19 female and 16 male healthy adults, inhibition (Abelson and Liberzon 1999; DeCherney et al. with a mean age of 26.3 Ϯ 7.7 years (range, 18–45 1985; Hermus et al. 1984; Schürmeyer et al. 1984), raising years). They were recruited through newspaper adver- questions about the role of CRH as mediator of the hu- tising, screened using the Structured Clinical Interview man HPA response to CCK agonism. A very rapid and for DSM-IV (SCID) to insure the absence of psychiatric robust release of AVP is seen in humans after CCK ago- disorders, and paid $100 for their participation. An ab- nist injection (Le Mellédo et al. 1997; Miaskiewicz et al. breviated Family Informant Schedule and Criteria in- 1989), supporting its potential role as mediator of CCK terview (Mannuzza et al. 1985) was used to exclude activation of the HPA axis. No human studies to date those with affective or anxiety disorders in first degree have simultaneously examined both ACTH and AVP relatives. Subjects had no recent (three months) serious responses to CCK receptor agonists. medical illness, no history of alcohol or drug depen- Functional interactions between CCK, AVP, and the dence, and no recent (six months) drug or alcohol HPA axis could be important to our understanding of a abuse. They did not smoke more than 20 cigarettes per number of clinical conditions. The CCK-B receptor is day or drink more than four cans of beer (or the equiva- thought to play a role in anxiety states (Bradwejn and lent) per week in the past 6 months. They were within Koszycki 1994; Harro et al. 1993) and CCK-B agonists Ϫ10% and ϩ25% of ideal body weight, had a negative reliably elicit panic attacks in the laboratory (Abelson urine drug screen, and had normal screening laboratory and Nesse 1994; Bradwejn et al. 1991; de Montigny tests (blood counts, electrolytes, glucose, liver and renal 1989). Panic patients show subtle abnormalities in HPA functions). Female subjects were pre-menopausal, were axis activity (Abelson and Curtis 1996), similar to those not taking birth control pills, and were studied within seen in patients with depression (Linkowski et al. 1985). the first 10 days after the onset of menstruation (to pre- Recent work suggests that HPA axis dysregulation in clude the possibility of pregnancy and control for ef- depression may be associated with a shift towards in- fects of menstrual cycle on the HPA axis). All subjects creased vasopressinergic control of the axis (Dinan et al. provided written informed consent. 1999; Holsboer and Barden 1996). Abnormalities in AVP levels or receptor activity have been detected in Procedures depression (Purba et al. 1996; van Londen et al. 1997) and obsessive-compulsive disorder (Altemus et al. Subjects were assigned (by constrained random assign- 1992), but have not yet been studied in other anxiety ment to give approximately equal age and gender dis- disorders. Evidence that AVP may play a role in condi- tributions in each group) to a placebo group or one of tioned fear (Stoehr et al. 1993), avoidance learning (In- four dose groups (0.2, 0.4, 0.6, and 0.8 ␮g/kg). The se- sel et al. 1999), and novelty sensitivity (Ehrenreich et al. lection of doses was based on the study’s primary focus 1996) suggests a possible relevance to phobic behavior on ACTH and cortisol (Abelson and Liberzon 1999). and panic. An AVP antagonist has shown some anxi- Subjects and nursing staff were blind to group assign- olytic activity in an animal model (Liebsch et al. 1996). ment. The experiment was conducted in a General Clin- Given the pharmacological and neuroanatomical ical Research Center (GCRC), where subjects were ad- NEUROPSYCHOPHARMACOLOGY 2001–VOL. 24, NO. 2 Vasopressin Response to Pentagastrin 163 mitted at 1:00 p.m. An intravenous catheter was added to plasma from patients with central diabetes in- inserted into a forearm or antecubital vein and kept sipidus to calculate recoveries (done with every assay). open with a normal saline drip.