Variations of motor activity following intraventricular (D-Pen2, D-Pen5)-enkephalin administration: interaction with acute uncontrollable foot-shock in mice.
The effects of intraventricular administration of (D-Pen2, D-Pen5)-enkephalin (DPDPE) (0.005, 1.0, and 2.5 micrograms/microlitter in a 1-microlitter vol.) on horizontal activity, rearing, and exploratory head dipping were assessed among CD-1 mice exposed to acute uncontrollable foot-shock 15 min following stressor termination. Foot-shock reduced horizontal activity, rearing, and exploratory head dipping during the immediate 15-min poststressor interval. Mice challenged with 0.005 micrograms DPDPE were behaviorally indistinguishable from vehicle-treated subjects. The 1.0-microgram dose of DPDPE increased horizontal activity in stressed and nonstressed subjects. Intraventricular infusion of 2.5 micrograms DPDPE potentiated horizontal activity in previously stressed mice but had no effect in nonstressed animals. The suppression of rearing and exploratory head dipping following uncontrollable foot-shock was not ameliorated by the delta-receptor agonist, and DPDPE was without effect on rearing and exploratory head dipping in nonstressed animals. Potential neurochemical mechanisms associated with the expression of these stressor associated behaviors are discussed.
Mendella
P D
PD
Unit for Behavioural Medicine and Psychopharmacology, Carleton University, Ottawa, Ontario, Canada.
Zacharko
R M
RM
D000700:Analgesics / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004597:Electroshock; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000008:administration & dosage / Q000494:pharmacology*; D005106:Exploratory Behavior / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects*; D017465:Receptors, Opioid, delta / Q000819:agonists; D013315:Stress, Psychological / Q000523:psychology*
D000700:Analgesics; D004745:Enkephalins; D017465:Receptors, Opioid, delta; D020881:Enkephalin, D-Penicillamine (2,5)-