[Effects of systemic administration of strychnine, L-allylglycine, bicuculline and picrotoxin on the transsynaptic neural destruction in the medullary dorsal horn following transection of the rat inferior alveolar nerve].

Adult rats underwent unilateral transection of the inferior alveolar nerve and subsequent intraperitoneal injection of strychnine (1 mg/kg, 3-23 days) at various posttransectional intervals. When they were sacrificed at 18-30 days posttransectionally, many pyknotic neuronal cell bodies were observed in plastic embedded toluidine blue-stained 1 micron-thick sections of the medullary dorsal horn. They were mostly found in the dorsal part of the dorsal horn ipsilateral to the neurotomy and were more abundant in laminae I/II than in laminae III/IV. Similar pyknotic neurons were found after 1 or 2 days of L-allylglycine administration (55.7 mg/kg/day) at a posttransectional interval of 20 days. Unlike those observed after strychnine treatment, the pyknotic neurons after L-allylglycine treatment were evenly distributed throughout laminae I-IV of the dorsal half of the medullary dorsal horn. Twenty-three days of bicuculline (2 mg/kg/day) or picrotoxin (0.5 mg/kg/day) treatment at an interval of 7 days did not yield pyknotic neurons. The results are discussed in the light of intrinsic synaptic circuitry of the dorsal horn.