INTRAHYPOTHALAMIC DISCRIMINATIVE STIMULUS EFFECTS OF NEUROPEPTIDE-Y

Neuropeptide Y (NPY) is one of the most ubiquitous neurotransmitters i n the CNS and has been implicated in a variety of psychological and ph ysiological functions. The current study investigated whether intrahyp othalamic (IH) administrations of NPY were behaviorally discriminable from saline injections. Rats were trained to differentially respond ba sed on whether they received IH injections of NPY (0.5 mu g/0.5 mu l) or saline (0.5 mu l 0.9% NaCl). Subjects demonstrated discriminative c ontrol (85% correct in 8 out of 10 consecutive sessions) after a mean of 32 sessions. The ability of subjects to discriminate IH NPY from sa line was dose dependent, with the lowest NPY dose tested (0.03 mu g/0. 5 mu l) generalizing to saline. The opioid antagonist naloxone blocked the discrimination of NPY when administered IP (3.0 mg/kg) or IH (50 mu g/0.5 mu l). (C) 1998 Elsevier Science Inc.