Organization of the guinea-pig uterine innervation. Distribution of immunoreactivities for different neuronal markers. Effects of chemical- and pregnancy-induced sympathectomy.

The structural organization of the guinea-pig uterine innervation was investigated by an immunofluorescence method using neurofibrillary protein (NF) and neuron-specific enolase (NSE) as general neuronal markers. NF- and NSE-immunoreactive nerve trunks and non-varicose nerves formed continuous networks similar to nerves with analogue morphology and with immunoreactivities for tyrosine hydroxylase (TH; adrenergic nerves) and neuropeptide Y (NPY). NF- and NSE-immunoreactive non-varicose nerves occurred in the myometrium and along vessels, where TH- and NPY-immunoreactive varicose nerves were also comparatively frequent. After chemical sympathectomy all TH- and NPY-immunoreactive varicose nerves and most NF- and NSE-immunoreactive non-varicose nerves disappeared, suggesting colocalization of TH, NPY, NF and NSE immunoreactivities. During pregnancy all NF-, NSE-, TH- and NPY-immunoreactive nerve structures disappeared in the foetus-bearing uterine horns whereas in the cervix and non-foetus-bearing uterine horns only the myometrial TH- and NPY-immunoreactive varicose nerves disappeared. After parturition there was a complete structural restoration of all types of immunoreactive nerves in previously non-foetus-related tissue. The reinnervation of this tissue followed a similar time-course to that after chemical sympathectomy. In contrast, the reinnervation of previously foetus-related tissue was much slower and incomplete. In conclusion, the whole autonomic uterine innervation undergoes overt structural changes during pregnancy and these changes are related to the foetus-bearing regions.