  We present optical spectroscopy of a sample of metal-rich extragalactic HII
regions in the spiral galaxies M83, NGC 3351 and NGC 6384, including a number
of circumnuclear HII regions (hot spots). Different age estimators (equivalent
width of the Hbeta emission line W(Hb), Balmer line absorption profiles, UV
spectra) provide consistently young ages (4-6 Myr) for the hot spots. We have
detected the W-R bump feature at 4650 A in five of the objects, and in fewer
cases possibly the WC features at 5696 A and 5808 A. Six additional objects
showing W-R features are drawn from our previous work on extragalactic HII
regions. From the measured luminosity of the W-R blue bump we estimate a small
number of WN stars (from 1-2 to about 30). By assuming instantaneous bursts of
star formation the ages derived from W(Hb) (3-6 Myr) and the strength of the
W-R bump are in agreement with the predictions of evolutionary stellar
population models, provided we account for stochastic effects on the IMF. From
a comparison with published photoionization models based on synthetic cluster
spectral energy distributions we find some evidence for an overestimation of
the number of He ionizing photons in the model fluxes. In general, however, the
massive star diagnostics are in agreement with the predictions of recent
evolutionary models calculated with a Salpeter IMF and a high mass limit. We
find no compelling evidence for a depletion of massive stars (M > 40-50 solar
masses) in the IMF of metal-rich clusters, contrary to our previous conclusions
based on older evolutionary models.
