Hypothalamic proline endopeptidase activity is not changed by various behavioral procedures.

ABSTRACT

Proline endopeptidase (E.C.3.4.21.26) is an enzyme which cleaves several neuropeptides at the carboxyl-side of proline residues. Some peptide substrates of this enzyme may be found in the rat hypothalamus (thyrotropin releasing hormone, neurotensin, substance P, oxytocin, vasopressin, beta-endorphin). Recent research has shown that the hypothalamic levels of some of these substances (e.g., vasopressin, beta-endorphin) change by a variety of training procedures. We studied the effect of various forms of training on the activity of proline endopeptidase of rat hypothalamus. The present results show that the activity of this enzyme is not altered by electroconvulsive shock or inhibitory avoidance training when measured, 0, 1, or 3 hr after these procedures. Other behavioral procedures (habituation to an open field, two-way active avoidance conditioning, or 1 min of inescapable footshock) also had no effect on hypothalamic proline endopeptidase activity measured immediately after training or test sessions. We conclude that proline endopeptidase probably does not play a regulatory role in the effect of synaptically released hypothalamic neuropeptides on behavior.