The Effects of β-Noradrenergic Receptor Blockade on Acquisition of Eyeblink Conditioning in 3-Month-Old F344 Rats

• Published in: Neurobiology of learning and memory 2002-09, Vol.78 (2), p.246-257
• Main Authors: Cartford, M.Claire, Allgeier, Chrissy A., Bickford, Paula C.
• Format: Article
• Language: English
• Subjects: Adrenergic beta-Antagonists - administration & dosage; Adrenergic beta-Antagonists - pharmacology; Animal; Animals; Behavioral psychophysiology; Biological and medical sciences; Blinking - drug effects; Conditioning; Conditioning (Psychology) - drug effects; Dose-Response Relationship, Drug; Electromyography; Fundamental and applied biological sciences. Psychology; Learning - drug effects; Learning. Memory; Male; Memory - drug effects; Neurotransmission and behavior; Propranolol - administration & dosage; Propranolol - pharmacology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Rats, Inbred F344; Receptors, Adrenergic - drug effects; Time Factors
• ISSN: 1074-7427; 1095-9564
• DOI: 10.1006/nlme.2002.4063

There is evidence that blocking β-noradrenergic receptors will cause deficits in some forms of learning. We investigated the effects of systemic injections of 1, 5, and 10 mg/kg doses of propranolol on acquisition of delay eyeblink conditioning in 3-month-old Fischer 344 rats. We presented a 3-kHz, 90-dB tone as a conditioning stimulus and a 6 psi airpuff as our unconditioned stimulus to freely moving rats. We monitored eyelid activity using EMG signals. The treatment subjects were injected with either propranolol or saline 0.5 h prior to daily training sessions. Two groups of control subjects, one receiving injections of saline and one receiving injections of 5 mg/kg propranolol, received daily training sessions with unpaired and randomized presentation of the tone and airpuff. Each daily training session for the treatment groups consisted of 27 paired training trials and 3 conditioned stimulus-alone training trials. Rats injected with saline vehicle or with 1 mg/kg propranolol achieved a 60% or better learned response rate within two training sessions. Rats injected with 5 or 10 mg/kg propranolol never achieved a response rate significantly different from animals that received unpaired, random presentations of the tone and airpuff stimuli. These results agree with prior studies from our lab that have shown a dose-dependent effect of β-noradrenergic receptor blockade on learning in rabbit eyeblink conditioning as well as in a runway, motor learning paradigm. We believe that the β-noradrenergic system plays an important role in learning and memory in more than one cerebellar-dependent learning paradigm.