ELECTROPHYSIOLOGICAL CHARACTERISTICS OF LOCUS-COERULEUS NEURONS IN THE MAUDSLEY REACTIVE (MR) AND NONREACTIVE (MNRA) RAT STRAINS

Extracellular single-unit recording techniques were used to evaluate t he physiological and pharmacological characteristics of noradrenergic locus coeruleus (LC) neurons in urethane-anesthetized Maudsley reactiv e (MR) and non-reactive (MNRA) rat strains, a presumed genetic model f or differences in 'anxiety'. LC neurons from MNRA rats were found to h ave a significantly higher basal discharge rate than LC neurons from e ither the MR or Sprague-Dawley (SD) rats. The discharge pattern of MNR A LC neurons also differed significantly from that of LC neurons from SD and MR rats, with LC neurons from MNRA rats exhibiting a burst-like pattern of discharge. Finally, MNRA LC neurons were significantly les s sensitive to the inhibitory effects of i.v. clonidine on spontaneous activity.