Effects of pentagastrin and the cold pressor test on the acoustic startle response and pupillary function in man

• Published in: Journal of psychopharmacology (Oxford) Vol. 14; no. 4; pp. 387 - 394
• Main Authors: Tavernor, S. J., Abduljawad, K. A. J., Langley, R. W., Bradshaw, C. M., Szabadi, E.
• Format: Journal Article
• Language: English
• Published: London, Thousand Oaks, CA and New Delhi SAGE Publications 01-07-2000; Sage; Sage Publications Ltd
• Subjects: Acoustic startle response; Activation; Adolescent; Adult; Anxiety; Behavioral psychophysiology; Biological and medical sciences; Blood pressure; Cold pressing; Cold Temperature - adverse effects; Cold treatment; Electromyography; Fundamental and applied biological sciences. Psychology; Heart rate; Heart Rate - drug effects; Hemodynamics - drug effects; Humans; Immersion; Infusions, Intravenous; Light effects; Male; Males; Miscellaneous; Pain Measurement - adverse effects; Panic; Pentagastrin - administration & dosage; Pentagastrin - pharmacology; Photic Stimulation; Pressure - adverse effects; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Reflex, Pupillary - drug effects; Reflex, Pupillary - physiology; Reflex, Startle - drug effects; Reflex, Startle - physiology; Reflexes; Startle response; Tachycardia; cold pressor test; anxiety; startle reflex; pentagastrin; panic; pupil; Human; Agonist; Pentagastrin; Intravenous administration; Healthy subject; Startle reflex; Subjective evaluation; Stress; Eye; Cholecystokinin receptor; Gastrointestinal hormone; Acoustic stimulus; Pupillary reflex; Anxiety; Hemodynamics; Mechanism of action; Blinking; Pentapeptide
• ISSN: 0269-8811; 1461-7285
• DOI: 10.1177/026988110001400407

Pentagastrin, a cholecystokinin2 (CCK2) receptor agonist, evokes autonomic and subjective features of anxiety in healthy volunteers. The present experiments examined the effects of pentagastrin on two responses with known sensitivity to another anxiogenic procedure (threat of electric shock): the acoustic startle response and the pupillary light reflex. The effects of pentagastrin were compared with those of the cold pressor test, a procedure known to elicit sympathetic activation. Twelve healthy males (18–35 years) participated in two experiments each consisting of two sessions in which they received (1) pentagastrin (0.3 µg/kg, i.v.) and a control infusion (saline), and (2) cold pressor test (90 s hand immersion at 4 °C) and a control immersion (37 °C), using a balanced single-blind protocol. Electromyographic responses of the orbicularis oculi to 40 ms, 1 kHz, 115 dB tones (‘startle responses’) [Experiment 1], and miotic responses to 200 ms, 0.43 mW/cm2 light pulses [Experiment 2] were recorded before, during and after the infusions and hand immersions. Heart rate, blood pressure and subjective feelings were also recorded. The amplitude of the startle response was not significantly affected by pentagastrin, but was reduced during the cold pressor test. Resting pupil diameter increased during both pentagastrin infusion and the cold pressor test, but neither procedure altered the amplitude of the light reflex. Tachycardia, increased blood pressure and subjective anxiety were induced by both pentagastrin and the cold pressor test. The cardiovascular and mydriatic effects of pentagastrin and the cold pressor test are consistent with the known ability of these treatments to induce sympathetic activation. The anxiety induced by these treatments, unlike anxiety induced by threat of electric shock, was not accompanied by potentiation of the startle response or reduction of the miotic response. The results indicate that different anxiogenic procedures do not have equivalent effects on these reflexes.