The present invention relates to compounds of formulae IA and IB wherein R.sup.1 and R.sup.2 are each independently lower alkyl or --(CH.sub.2).sub.m--O-lower alkyl, or together with the N atom to which they are attached form a heterocyclic ring; R.sup.3 is hydrogen or lower alkyl; R.sup.4 is lower alkyl; hetaryl is 3H-imidazole-2,4-diyl or 1H-pyrazole-1,4-diyl; n is 1 or 2; and m is 1 or 2; and to pharmaceutically acceptable acid addition salts thereof. These compounds may be used for the treatment of Alzheimer's disease, Parkinson's disease, Huntington's disease, neuroprotection, schizophrenia, anxiety, pain, respiration deficits, depression, ADHD, drug addiction, such as amphetamine, cocaine, opioids, ethanol, nicotine, cannabinoids, or for the treatment of asthma, allergic responses, hypoxia, ischaemia, seizure and substance abuse, or for use as sedatives, muscle relaxants, antipsychotics, antiepileptics, anticonvulsants and cardiaprotective agents for coronary artery disease and heart failure.