Effects of scopolamine on smell discrimination in the rat

Abstract

Earlier work suggested that scopolamine might cause a blockade of olfactory perception. Rats were trained to perform a smell-discrimination and head-poke response for food reinforcement. Following treatment with saline or scopolamine (SeOl, rats were retested on these two tasks as well as on passive avoidance. Scopolamine significantly impaired passive avoidance and head-poke responding. Scopolamine also caused a delay in the onset of discrimination performance. There was a significant disruption of smell discrimination on early trials, during which seo rats failed to execute choices, whether correct or incorrect. However, when seo rats began to execute choices, their choices were correct. They showed a significant improvement over trials and maintained near-perfect discrimination on the second half of the test. The results of the smell-discrimination test indicate that scopolamine did not cause a complete blockade of olfactory perception. The results of the head-poke test suggest that scopolamine might increase vibrissae sensitivity.

Age-related scopolamine effects on social and individual behaviour in rats

“…Another explanation could be a possible interaction between scopolamine and olfaction. It has been shown that cholinergic antagonists affect the activity of neurons in olfactory bulbs (review in Kasa 1986) and could produce some olfactory impairments without rendering the rat anosmic (Mollenauer et al 1976). The importance of olfaction in agonistic behaviour was often underlined (Blanchard et al 1975;Lumia et al 1975).…”

No Influence of Scopolamine Hydrobromide on Odor Detection Performance of Rats

“…Although alterations in odor-mediated learning and memory tasks following the administration of cholinergic drugs have been reported in animals (Mollenauer et al, 1976;Cheal, 1981;Soffie and Lamberty, 1988;Hunter and Murray, 1989;Ravel et al, 1992Ravel et al, , 1994, odor detection per se has not been measured. Conceivably a number of such effects could reflect decreased smell function, rather than alterations in memory encoding.…”

“…Limited support for this notion came from early observations that scopolamine reduced the fear response of rats to cats (Plotnik et al, 1974) and that olfactory bulbectomy had a similar effect (Mollenauer et al, 1974). The possibility that olfactory sensitivity was altered by scopolamine was tangentially supported by evidence that ether-soaked cotton balls failed to induce a typical head-turning response in scopolaminetreated rats (Mollenauer et al, 1976).…”

“…In light of these findings, Mollenauer et al (1976) trained 13 rats to perform a two-choice odor discrimination task in which responding to the odor of wet Purina lab chow (versus no odor) was reinforced using sucrose pellets; subsequently, six of the rats were administered 0.8 mg/kg scopolamine hydrobromide and their performance compared with the remaining rats, who received saline alone. Although the scopolamine-treated rats evidenced decreased performance on the first 10 of 20 test trials, their performance on the last 10 trials was normal.…”

Handbook of Psychopharmacology

“…Impaired learning has subsequently been shown in studies using pretreatment with cholinergic antagonists in both rats (Berger andStein. 1969: Blozovski andHennocq, 1982;Feigley, 1974;Mollenauer et al, 1976;Wilson and Riccio, 1976) and mice (Calhoun and Smith, 1968;Calhoun I'f at., 1970;Bohdaneckv and Jarvik, 1967;Dilts and Berry, 1967;Glick and Zimmerberg, 1971). Intraventricular injections of pyrrolcholine, a choline analog that competes for uptake and is converted to acetylpyrrolcholine (an inactive form of the transmitter), also impair initial learning (Glick et al .. 197:)).…”