Play behavior in rats pretreated with scopolamine: Increased play solicitation by the non-injected partner
Terrence Deak a,*, Jaak Panksepp b,c
Behavioral Neuroscience Program, Department of Psychology, State University of New York at Binghamton, Vestal Parkway East, Binghamton, NY 13902-6000, United States
J.P. Scott Center for Neuroscience, Mind and Behavior, Bowling Green State University, Bowling Green, OH 43403, United States Center for the Study of Animal Well-Being, Veterinary and Comparative Anatomy, Pharmacology and Physiology (VCAPP), Washington State University, Pullman, WA 99164-6520, United States
Received 1 April 2005; received in revised form 9 September 2005; accepted 13 September 2005
Play behavior was assessed in juvenile rat pups following chronic administration of scopolamine (0.5 or 1.0 mg/kg, i.p.) to one partner in each dyad of rats. Scopolamine administration significantly reduced the number of pins and mean pin duration of both playmates in pairs where only one rat was injected with scopolamine (irrespective of dose). However, dorsal contacts were significantly increased in rats exposed to a play partner that had been injected with scopolamine, indicating an increase in play solicitation when the partner was rendered non-responsive with this drug. These effects were stable and consistent over the course of 15 days of repeated testing in the presence of scopolamine. In other words, normal animals did not extinguish play solicitation even after prolonged periods of non-reciprocity. Upon cessation of drug treatment, play behavior returned largely to normal in both animals. Overall locomotor activity levels were significantly reduced in pairs where one rat had been injected with scopolamine. Together, these data suggest that the effects of repeated scopolamine are acute in nature, and that disruption of normal play behavior following chronic scopolamine treatment does not produce long-term impairments in social play behavior beyond acute action of the drug. D 2005 Elsevier Inc. All rights reserved.
Keywords: Scopolamine; Play behavior; Social interaction; Motivation; Rat
In the study of dynamic social interactions such as roughand-tumble play it is often difficult to analyze neural substrates underlying these processes because a variety of behavioral,
cognitive, and emotional processes are interacting simultaneously in complex and seemingly inextricable patterns . One way to simplify the analysis of juvenile play interactions has been to pharmacologically induce a state of non-playfulness in one animal of a play dyad. This provides a non-playful target for the play-solicitations of the non-drugged animal. Although this could be achieved in various ways, the most
common has been to give one animal of a play pair high doses of anti-cholinergic agents such as scopolamine [20,21]. The
advantage of such agents is that while anti-muscarinic drugs * Corresponding author. Tel.: +1 607 777 5918; fax: +1 607 777 4890. E-mail address: firstname.lastname@example.org (T. Deak).
0031-9384/$ - see front matter D 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.physbeh.2005.09.009
dramatically reduce playfulness, animals continue to locomote and to show social investigation [16,18,23], which is not the case with immobilizing agents such as high doses of opiates
an d do p a m i n e b l o ck i n g a ge n t s , b o t h o f w h i ch c an a l s o markedly reduce play . Thus, if one animal of a play pair is given scopolamine, the other animal still has a moving target toward which to direct play-solicitations such as darting and pouncing with dorsal contacts or nape attacks .
Previous work has utilized such procedures to dissect the
reinforcing value of social play [5,16], the motivation of
neurologically impaired animals to solicit play , the effects of neurotoxicological interventions on social motivation...