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This investigation examined receptor subtype specificity and possible modulation by GABAa receptor ligands of NPY-induced behavioral responses to stressful stimuli. First, a series of NPY receptor agonists were examined for their potential effects on punished responding in a conflict test modified for incremental shock. NPY, peptide YY (PYY) and NPY Y1 receptor agonists [Leu31,Pro34]-NPY and [Gly6, Glu26,Lys26,Pro34]-NPY produced increases in punished responding in the conflict test. No significant effects on unpunished responding were noted. The pattern of responding was similar to that observed with the benzodiazepine agonist chlordiazepoxide. Neither pancreatic peptide (PP) nor the Y2 agonists NPY13-36 or [Glu2,32,Ala6,Dpr27,Lys28]-NPY significantly altered punished or unpunished responding. Of significance, the atypical Y1 agonist [Cys7,21,Pro34]-NPY produced negligible effects on punished responding, consistent with the presence of a subclass of Y1 receptors. Second, the anxiolytic effects of NPY were subjected to treatments that block actions at the GABAa receptor complex. The increase in punished responding produced by NPY was not altered by administration of the benzodiazepine antagonist flumazenil and only partially blocked by the picrotoxinin receptor ligand isopropylbicyclophosphate (10 and 15 microg/kg). These findings further support the hypothesis that the pharmacologic substrates for the anxiolytic-like actions of NPY may be mediated by the Y1 receptor subtype and suggest that these actions are independent of either the benzodiazepine or picrotoxinin binding sites of the GABA/benzodiazepine receptor complex.

The ability of MALDI-MS to analyze photolabile arylazido peptide derivatives was investigated. Peptides containing UV-labile p-azidobenzoyl groups were subjected to MALDI-MS analysis in a variety of matrices. As standard MALDI-MS employs a UV laser (337 nm), we investigated conditions that would allow detection of the intact molecule ions for these light-sensitive peptides. When using α-cyano-4-hydroxycinnamic acid (ACHC) or 2,5 dihydroxybenzoic acid (DHB) as the matrix, photoinduced degradation products were prevalent. In contrast, when employing the matrix sinapinic acid, the intact molecule ion corresponding with the azido peptide was the predominant signal. The protection of photolabile azido derivatives correlates with the UV absorbance properties of the matrix employed, i.e., sinapinic acid, which exhibits a strong absorbance near 337 nm, most efficiently protects the azido derivative from photodegradation.