Castration in rats impairs performance during acquisition of a working memory task and exacerbates deficits in working memory produced by scopolamine and mecamylamine.
BACKGROUND
Although much research has focused on the effects of ovarian hormones on learning and memory in females, less information is available regarding the effects of testicular hormones on learning and memory in males. Additionally, despite evidence of an interaction of testicular hormones and the cholinergic system in areas of the brain implicated in learning and memory, no information is available regarding the behavioral consequences of that interaction.


OBJECTIVE
We assessed the effect of castration in male rats on working memory during acquisition of a radial maze. We also assessed the interactive effects of castration and scopolamine, a muscarinic receptor antagonist, as well as mecamylamine, a nicotinic receptor antagonist, on behavior.


METHODS
Young adult male rats were castrated or underwent sham surgeries. Beginning 10 days after surgeries, performance on a task of working memory was assessed across 24 days of acquisition in an eight-arm radial maze. Following acquisition, scopolamine and mecamylamine dose-effect curves were established.


RESULTS
Castration of male rats significantly decreased arm-choice accuracy during acquisition. Castration significantly exacerbated impairments in arm-choice accuracy produced by scopolamine as well as mecamylamine, without altering the disruptive effects of the drugs on the rate at which rats entered the arms of the maze.


CONCLUSIONS
These results indicate that castration in male rats impairs working memory during acquisition of a spatial maze task. Additionally, these results suggest that the absence of testicular hormones increases the sensitivity of male rats to the impairing effects of scopolamine as well as mecamylamine on working memory.
Daniel
Jill M
JM
Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA. jdaniel@uno.edu.|Department of Psychology, University of New Orleans, New Orleans, LA 70148, USA. jdaniel@uno.edu.
Winsauer
Peter J
PJ
Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA.
Moerschbaecher
Joseph M
JM
Department of Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005730:Ganglionic Blockers / Q000633:toxicity*; D008297:Male; D018782:Maze Learning / Q000187:drug effects*; D008464:Mecamylamine / Q000633:toxicity*; D008569:Memory Disorders / Q000139:chemically induced* / Q000209:etiology; D018727:Muscarinic Antagonists / Q000633:toxicity*; D009919:Orchiectomy; D051381:Rats; D012601:Scopolamine / Q000633:toxicity*; D013735:Testicular Hormones / Q000502:physiology*
D005730:Ganglionic Blockers; D018727:Muscarinic Antagonists; D013735:Testicular Hormones; D008464:Mecamylamine; D012601:Scopolamine